This is the accessible text file for GAO report number GAO-04-54 
entitled 'Aviation Safety: More Research Needed on the Effects of Air 
Quality on Airliner Cabin Occupants' which was released on February 10, 
2004.

This text file was formatted by the U.S. General Accounting Office 
(GAO) to be accessible to users with visual impairments, as part of a 
longer term project to improve GAO products' accessibility. Every 
attempt has been made to maintain the structural and data integrity of 
the original printed product. Accessibility features, such as text 
descriptions of tables, consecutively numbered footnotes placed at the 
end of the file, and the text of agency comment letters, are provided 
but may not exactly duplicate the presentation or format of the printed 
version. The portable document format (PDF) file is an exact electronic 
replica of the printed version. We welcome your feedback. Please E-mail 
your comments regarding the contents or accessibility features of this 
document to Webmaster@gao.gov.

This is a work of the U.S. government and is not subject to copyright 
protection in the United States. It may be reproduced and distributed 
in its entirety without further permission from GAO. Because this work 
may contain copyrighted images or other material, permission from the 
copyright holder may be necessary if you wish to reproduce this 
material separately.

Report to the Ranking Democratic Member, Subcommittee on Aviation, 
Committee on Transportation and Infrastructure, House of 
Representatives:

January 2004:

AVIATION SAFETY:

More Research Needed on the Effects of Air Quality on Airliner Cabin 
Occupants:

GAO-04-54:

GAO Highlights:

Highlights of GAO-04-54, a report to the Ranking Democratic Member, 
Subcommittee on Aviation, Committee on Transportation and 
Infrastructure, House of Representatives 

Why GAO Did This Study:

Over the years, the traveling public, flight attendants, and the 
medical community have raised questions about how airliner cabin air
quality contributes to health effects, such as upper respiratory 
infections. Interest in cabin air quality grew in 2003 when a small 
number of severe acute respiratory syndrome (SARS) infections may have 
occurred on board aircraft serving areas that were experiencing 
outbreaks of the disease. In 2001, a National Research Council report 
on airliner cabin air quality and associated health effects 
recommended that additional research be done on the potential health 
effects of cabin air.

GAO reviewed what is known about the health effects of cabin air, the 
status of actions recommended in the 2001 National Research Council 
report, and whether available technologies should be required to 
improve cabin air quality.


What GAO Found:

Despite a number of studies of the air contaminants that airline 
passengers and flight attendants are potentially exposed to, little is 
known about their associated health effects. Reports on airliner cabin 
air quality published by the National Research Council in 1986 and 
2001 concluded that more research was needed to determine the nature 
and extent of health effects on passengers and cabin crew. Although 
significant improvements have been made to aircraft ventilation 
systems, cabin occupants are still exposed to allergens and infectious 
agents, airflow rates that are lower than those in buildings, and air 
pressures and humidity levels that are lower than those normally 
present at or near sea level. 

The 2001 National Research Council report on airliner cabin air 
quality made 10 recommendations, 9 of which directed the Federal 
Aviation Administration (FAA) to collect more data on the potential 
health effects of cabin air and to review the adequacy of its 
standards for cabin air quality. FAA has addressed these 9 
recommendations to varying degrees as it attempts to balance the need 
for more research on cabin air with other research priorities (e.g., 
passenger safety). However, some in the aviation community, including 
some of the committee members who produced the report on cabin air, do 
not feel that FAA’s planned actions will address these recommendations 
adequately. For example, most members were concerned that FAA’s plan 
for implementing the report’s key recommendations on the need for more 
comprehensive research on the health effects of cabin air was too 
limited. FAA plans to address these recommendations in two parts—the 
first, which started in December 2003, and the second, which will 
start in December 2004 and end in late 2006 or early 2007. However, 
FAA lacks a comprehensive plan, including key milestones and funding 
needs. In addition, most committee members thought that FAA’s response 
to a recommendation for it to improve public access to information on 
the health risks of flying was inadequate. We also had difficulty 
accessing this information on FAA’s Web site. 

Several technologies are available today that could improve cabin air 
quality, (e.g., increasing cabin humidity and pressure or absorbing 
more cabin odors and gasses); however, opinions vary on whether FAA 
should require aircraft manufacturers and airlines to use these 
technologies. GAO found that one available technology, high-efficiency 
particulate air (HEPA) filtering, was strongly endorsed by cabin air 
quality and health experts as the best way to protect cabin occupants'
health from viruses and bacteria in recirculated cabin air. While FAA 
does not require the use of these filters, GAO’s survey of major U.S. 
air carriers found that 85 percent of large commercial airliners in 
their fleets that recirculate cabin air and carry more than 100 
passengers already use these filters. However, the use of HEPA filters 
in smaller commercial aircraft that carry fewer than 100 passengers is 
much lower. The cost to retrofit the smaller aircraft to accept the 
HEPA filter, if it were made mandatory, could be expensive.

What GAO Recommends:

GAO recommends that FAA develop detailed plans for its research and 
surveillance program on cabin air quality, improve the public’s access 
to information on the health risks of flying, and assess the costs and 
benefits of requiring HEPA filters in commercial aircraft.

www.gao.gov/cgi-bin/getrpt?GAO-04-54.

To view the full product, including the scope and methodology, click 
on the link above. For more information, contact Gerald L. Dillingham 
at (202) 512-2834 or dillinghamg@gao.gov.

[End of section]

Contents:

Letter: 

Results in Brief: 

Background: 

Despite a Number of Studies, Data Are Lacking About the Effects of Air 
Quality On Cabin Occupants: 

FAA has Taken Action to Address Council Recommendations On Cabin Air 
Quality, but These Efforts Could Be Improved: 

Some Technologies Exist for Improving Cabin Air Quality, but There Are 
Questions About Whether They Should be Required: 

Conclusions: 

Recommendations for Executive Action: 

Agency Comments: 

Appendixes:

Appendix I: Objectives, Scope, and Methodology: 

Appendix II: Biographical Information on the National Research Council 
Committee: 

Appendix III: Transmission of Severe Acute Respiratory Syndrome (SARS) 
on Board Aircraft Is Rare and Associated with Proximity: 

Appendix IV: European CabinAir Study: Scope and Methodology: 

Appendix V: Surveillance and Research Programs: 

Surveillance Program: 

Research Program: 

Appendix VI: GAO Contacts and Staff Acknowledgments: 

GAO Contacts: 

Staff Acknowledgments: 

Selected Bibliography:

Tables: 

Table 1: Potential Air Quality Related Concerns on Aircraft Cited by 
the National Research Council in 2001: 

Table 2: Status of the National Research Council's 2001 Report 
Recommendations on Airliner Cabin Air Quality: 

Table 3: Number of Large and Regional Aircraft of Top 28 Airlines That 
Do or Do Not Recycle Cabin Air: 

Figures: 

Figure 1: Passenger Cabin of Commercial Airliner: 

Figure 2: Overview of How Air Is Supplied on a Commercial Airliner: 

Figure 3: A Typical HEPA Filter for Commercial Passenger Aircraft: 

Abbreviations: 

AFA: Association of Flight Attendants:

APFA: Association of Professional Flight Attendants:

APL: Applied Physics Laboratory (Johns Hopkins University):

ASHRAE: American Society of Heating, Refrigerating and Air-Conditioning 
Engineers:

AsMA: Aerospace Medical Association:

ATA: Air Transport Association:

ATR: Avions de Transport Regional:

BAe: British Aerospace:

BRE: Building Research Establishment:

CAA: Civil Aviation Authority (United Kingdom):

CDC: Centers for Disease Control and Prevention:

CO: carbon monoxide:

CO2: carbon dioxide:

DOT: Department of Transportation:

ECS: Environmental Control System:

EPA: Environmental Protection Agency:

FAA: Federal Aviation Administration:

FARS: Federal Aviation Regulations:

GAO: General Accounting Office:

HEPA: high-efficiency particulate air:

IAPA: International Airline Passengers Association:

IATA: International Air Transport Association:

JAA: European Joint Aviation Authorities:

NEJM: New England Journal of Medicine:

NIOSH: National Institute for Occupational Safety and Health:

NRC: National Research Council:

O3: ozone:

RPM: revenue passenger mile:

SARS: severe acute respiratory syndrome:

TB: tuberculosis:

URI: upper respiratory tract infection:

WHO: World Health Organization

Letter January 16, 2004:

The Honorable Peter DeFazio: 
Ranking Democratic Member: 
Subcommittee on Aviation: 
Committee on Transportation and Infrastructure: 
House of Representatives:

Dear Mr. DeFazio:

The quality of air in commercial airliner cabins has long been a 
concern of the traveling public, the medical community, and 
particularly flight attendants, who fly often. Air quality, in the 
context of airliner cabins, refers to the extent to which airflow, low 
humidity, and air pressure[Footnote 1] and contaminants such as 
pollutants and infectious disease pathogens affect the healthfulness of 
the air. Air travelers, flight attendants, and the medical community 
have raised questions about the extent to which cabin air contributes 
to discomfort, such as dry eyes and nose, and to more serious health 
effects, such as upper respiratory infections. Interest in cabin air 
quality heightened in 2003, with reports that a small number of severe 
acute respiratory syndrome (SARS) infections may have occurred on board 
aircraft serving areas with SARS outbreaks.[Footnote 2] In 2001, the 
National Research Council[Footnote 3] issued a report that assessed 
airborne contaminants in commercial aircraft, including an evaluation 
of their toxicity and associated health effects; addressed cabin 
pressure (oxygen supply) and ventilation; and recommended approaches to 
improving data on cabin air quality.[Footnote 4]

Given this backdrop, you asked us to provide information on steps that 
the aviation community is taking to address concerns about cabin air 
quality. Specifically, you asked us to address the following questions: 
(1) What is known about the major potential health effects of air 
quality in commercial airliner cabins on passengers and flight 
attendants? (2) What actions has the National Research Council 
recommended to improve cabin air quality, and what is the status of 
those actions? (3) What technologies are available today to improve the 
air quality in commercial airliner cabins, and which, if any, should be 
required?

To address these questions we reviewed the December 2001 National 
Research Council report on airliner cabin air quality because it was 
the most current and comprehensive work of its kind in this area. The 
Council is the principal operating agency of the National Academy of 
Sciences, which was chartered by Congress to advise the federal 
government on scientific and technical matters. To produce the report, 
the Council convened a committee of experts in the fields of industrial 
hygiene, exposure assessment, toxicology, occupational and aerospace 
medicine, epidemiology, microbiology, aerospace and environmental 
engineering, air monitoring, ventilation and airflow modeling, and 
environmental chemistry. (App. II lists the members of the committee.) 
The committee examined the existing literature on this issue and made 
recommendations for potential approaches for improving cabin air 
quality. We also independently reviewed other studies on issues related 
to cabin air quality, paying particular attention to those issued after 
the publication of the National Research Council report.[Footnote 5] We 
also gathered information from airlines and the governments of 
Australia, Canada, and the United Kingdom because of the research these 
countries have done on airliner cabin air quality. We also interviewed 
officials representing the World Health Organization (WHO), the Centers 
for Disease Control and Prevention (CDC), the Federal Aviation 
Administration (FAA), the National Institute for Occupational Safety 
and Health (NIOSH), the Aerospace Medical Association (AsMA), the Air 
Transport Association (ATA), the Association of Flight Attendants 
(AFA), the International Airline Passengers Association (IAPA), and 
aircraft and air filter manufacturers. We also interviewed several 
recognized experts on cabin air quality issues. In addition, we 
interviewed 11 of the 13 members[Footnote 6]of the National Research 
Council Committee on Air Quality in Passenger Cabins of Commercial 
Aircraft that produced the 2001 report to obtain their views on the 
status of the report's recommendations and other cabin air quality 
issues, including leveraging expertise outside of FAA, such as the 
Environmental Protection Agency for its large body of research on 
indoor air quality and NIOSH for its role in conducting public health 
and air quality research. Finally, we contacted the 14 largest U.S. 
airlines that use Airbus, Boeing, or McDonnell Douglas aircraft to 
determine the extent to which their aircraft fleets use high-efficiency 
particulate air (HEPA) filters[Footnote 7] on recirculated cabin air. 
Twelve of these 14 airlines responded, allowing us to determine HEPA 
filter usage rates for approximately 90 percent of the aircraft in our 
study population. We also obtained information from an aviation 
publication and the manufacturers of regional jets (typically aircraft 
that seat 100 or fewer passengers) on the extent of HEPA filter usage 
in these aircraft. We conducted our work from April 2003 through 
December 2003 in accordance with generally accepted government auditing 
standards. See appendix I for additional information on our objectives, 
scope, and methodology.

Results in Brief:

Despite a number of studies of the air contaminants that passengers and 
flight attendants are potentially exposed to in airliner cabins and 
complaints by cabin occupants about health effects from poor cabin air 
quality, little is known about the extent of associated health effects. 
Reports published by the National Research Council in 1986 and 2001 on 
what was then known about airliner cabin air quality concluded that 
more research was needed to determine the nature and extent of health 
effects on passengers and cabin crew and that available air quality 
data are not adequate to address critical questions on aircraft cabin 
air quality and its possible effects on cabin occupant health. While 
aircraft manufacturers have made significant improvements to aircraft 
ventilation systems, passengers and cabin crews are still exposed to a 
number of air contaminants, such as allergens and infectious agents. 
Passengers and crew are also subjected to airflow rates that are lower 
than those recommended for buildings and to air pressures and humidity 
levels that are lower than those normally present at or near sea level. 
This exposure can pose a health risk to passengers with certain medical 
conditions, such as lung, heart, and circulatory disorders. In 
addition, poor cabin air quality has been associated with such 
discomforts as eye and nasal passage irritation.

The 2001 National Research Council report on airliner cabin air quality 
made 10 recommendations directed largely to the Federal Aviation 
Administration (FAA) to collect more information on the potential 
health effects of cabin air quality and to review the adequacy of its 
standards for air quality in commercial airliner cabins. To varying 
degrees, the agency has addressed the recommendations for which it is 
responsible. FAA is attempting to balance the need for additional 
research on the potential health effects of cabin air quality with 
other research priorities, such as improving passenger safety. However, 
some in the aviation community, including members of the Council 
committee who prepared the report, do not feel that FAA's planned 
actions will adequately address all of its recommendations on cabin air 
quality. For example, several of the Council committee members were 
particularly concerned about FAA's approach to implementing the 
committee's principal recommendations that more comprehensive research 
on the health effects of cabin air quality is needed. In response to 
the committee's recommendations in this area, FAA is leading the 
development of a surveillance and research program intended to relate 
perceptions of discomfort or health-related symptoms of flight 
attendants and passengers to possible causal factors, such as air 
contaminants, reduced air pressures and airflows, jet lag, low 
humidity, or inactivity. However, FAA has not yet developed a detailed 
plan with key milestones and funding estimates for conducting the 
planned surveillance and research program. In addition, of the 8 
committee members who discussed the recommendations with us,[Footnote 
8] all said that FAA's program was much more limited than the Committee 
had envisioned. For example, 2 of the 8 said that FAA's program does 
not include an adequate number and cross-section of aircraft types and 
flights for accomplishing its objective. One committee member was also 
concerned that the program is too heavily tied to the aircraft industry 
to ensure objectivity and independence. In addition, another committee 
member believes that although FAA has a committee to oversee the 
selection of the contractor for the program, it has not assembled an 
advisory committee to review the research design and monitor the 
implementation of the program. In addition, 3 committee members are 
concerned that the research effort may not be adequately funded. 
Furthermore, 6 of the committee members felt that FAA's approach for 
addressing its recommendation that increased efforts be made to provide 
cabin crew, passengers, and health professionals with information on 
health issues related to flying by creating links on the FAA Web site 
to relevant information from health organizations was inadequate 
because the links are difficult to navigate and need to be supplemented 
with other information dissemination methods, such as providing 
physicians with brochures to share with patients who are planning air 
travel.

Several technologies are available today that could improve cabin air 
quality (e.g., by filtering or removing contaminants, increasing cabin 
humidity and raising cabin pressure, or absorbing more cabin odors and 
gasses), but opinions vary on whether FAA should require aircraft 
manufacturers and airlines to use these technologies. Aircraft 
manufacturers contend that unless future research proves otherwise, the 
ventilation systems in the aircraft that they have produced provide 
ample amounts of relatively clean air. Most aircraft currently in 
production have ventilation systems that recirculate cabin air. In 
addition, all of the new large commercial airliners in production that 
carry more than 100 passengers and have ventilation systems that 
recirculate cabin air come equipped with high-efficiency particulate 
air (HEPA) filters, which are highly effective (99.97 percent) at 
capturing airborne contaminants, such as viruses, when properly fitted 
and maintained. According to our survey of major U.S. air carriers, 85 
percent of commercial airliners in the current U.S. fleet that 
recirculate cabin air and carry more than 100 passengers use HEPA 
filters. However, we found that only a small portion of the smaller 
regional jets that recirculate cabin air are using these filters. 
According to the manufacturers, most of these aircraft have no 
provision for installing any type of filter for their recycled air and 
could not be retrofitted with HEPA filters without extensive 
modifications. Nevertheless, given the proven effectiveness of HEPA 
filters, some National Research Council committee members and health 
officials believe that FAA should require them on all aircraft with 
recirculation systems. GAO also found that HEPA filters are relatively 
low cost when their use does not require modifying the existing 
ventilation system. In addition, airflow rates could be increased in 
some aircraft by adjusting settings on the ventilation system to reduce 
the effects of some airborne contaminants by diluting their 
concentration. However, this would be done at the expense of higher 
fuel consumption, increased engine emissions, and lower cabin humidity. 
Finally, both Boeing and Airbus--the world's two largest airframe 
manufacturers--are considering using air quality improvement 
technologies (e.g., increasing cabin humidity) to improve passenger 
comfort on the long-range commercial aircraft that they are developing.

To help ensure that FAA's research and surveillance efforts on airliner 
cabin air quality answer critical outstanding questions about the 
nature and extent of potential health effects of cabin air quality on 
passengers and flight attendants, GAO recommends that the FAA 
Administrator (1) develop a detailed plan for the research and 
surveillance efforts, including key milestones and funding estimates; 
(2) appoint a committee of acknowledged experts in the fields of 
aircraft ventilation and public health, including representatives of 
EPA and NIOSH, to assist in planning and overseeing the research and 
surveillance efforts; (3) leverage the findings of international 
counterparts' research on airliner cabin air quality to inform FAA's 
surveillance and research efforts; and (4) report to Congress annually 
on the progress and findings of the research and surveillance efforts 
and funding needs.

In addition, to help improve the healthfulness of cabin air for 
passengers and cabin crews, GAO also recommends that the FAA 
Administrator assess the costs and benefits of requiring the use of 
HEPA filters on commercial aircraft with ventilation systems that 
recirculate cabin air. GAO also recommends that FAA should go farther 
in addressing the Council recommendation to increase efforts to provide 
the public with information on the health risks of flying by taking 
additional steps to improve its methods for disseminating this 
information, such as improving the ease with which the public can 
access this information on FAA's Web site and systematically 
disseminating such information to physicians and their patients through 
various medical associations.

Background:

Since people began traveling in pressurized, climate-controlled 
aircraft more than 40 years ago, questions have arisen about the 
quality of air inside aircraft cabins and its effect on the health of 
passengers and cabin crews. In addition, the number of people traveling 
by commercial aircraft has increased dramatically over the years, with 
more than 600 million passengers flown by U.S. carriers in 2002 alone. 
Despite a downturn in air travel following the events of September 11, 
2001, FAA expects demand to recover and then continue a long-term trend 
of 3.6 percent annual growth. As air travel has become more accessible, 
the flying public mirrors the general population more closely than in 
years past. Therefore, it includes more young and elderly passengers 
who can be more susceptible to potential health risks associated with 
air travel. This diverse group of passengers, as well as the cabin 
crew, experiences an environment in the aircraft cabin that in some 
ways is similar to that of homes and buildings but in other ways is 
distinctly different. The National Research Council (the Council)--the 
principal operating agency of the National Academy of Sciences--has 
issued two reports at the request of Congress on the air quality in 
aircraft cabins, one in 1986 and another in 2001.[Footnote 9] The 2001 
Council report notes that the aircraft cabin is a unique environment in 
which the occupants are densely confined in a pressurized space. The 
report goes on to note that airline passengers encounter environmental 
factors that include low humidity, reduced air pressure, and potential 
exposure to air contaminants, including ozone, carbon monoxide, 
pesticides, various organic chemicals, and biological agents that can 
have serious health effects. The report concluded that there are still 
many unanswered questions about how these factors affect cabin 
occupants' health and comfort and about the frequency and severity of 
incidents in which heated oils or hydraulic fluids release contaminants 
into the cabin ventilation system. Figure 1 shows the passenger cabin 
of a commercial aircraft.

Figure 1: Passenger Cabin of Commercial Airliner:

[See PDF for image]

[End of figure]

As depicted in figure 2, supplying air to modern jet airliner cabins is 
a complex process that varies somewhat among airplane models but has 
essential characteristics that are shared by most airliners. Basically, 
some of the outside air that enters the aircraft engines is diverted 
and processed for use in the cabin in order to achieve an air pressure 
and temperature closer to that experienced on the earth's surface. FAA 
requires that air supplied to aircraft be designed to maintain a cabin 
pressure equivalent to that at an elevation of no more than 8,000 feet, 
which is similar to the elevation of Mexico City (7,500 ft.). 
Nevertheless, the air pressures inside aircraft cabins are much higher 
than the extremely low outside air pressures at normal cruising 
altitudes of 25,000 to 40,000 feet. After flowing through the engines, 
the air enters an intricate system of cooling devices and ducts and is 
distributed throughout the cabin and cockpit. Airlines that fly in 
areas where ozone levels are high[Footnote 10] are required to take 
steps to ensure that ozone levels do not exceed prescribed standards 
(e.g., by having a device that converts the ozone pollutant into oxygen 
before it enters the cabin and cockpit). The Council reported that 
unacceptable high ozone levels can occur in passenger cabins of 
commercial aircraft in the absence of effective controls. On most 
modern aircraft, an average of about 56 percent of the outside air 
supplied to the cabin is vented out of the aircraft through valves that 
help regulate cabin pressure. The remaining air is then recirculated 
through the cabin; this recirculation allows the engines to use less 
fuel for air supply and pressurization. In addition to less fuel and 
pressurization, recirculation also provides the benefit of higher 
airplane cabin humidity, improved airflow patterns, and minimized 
temperature gradients. On most large aircraft, the recirculated air 
typically passes through filters that are designed to remove harmful 
particulates, such as viruses and bacteria.[Footnote 11] FAA requires 
that aircraft ventilation systems for aircraft designs certified after 
June 1996 be designed to supply at least 10 cubic feet per minute of 
outside air per person under standard operating conditions. This 
compares with the standard minimum rate of 15 cubic feet per minute per 
person for buildings recommended by the American Society of Heating, 
Refrigerating and Air-Conditioning Engineers (ASHRAE).[Footnote 12] 
However, according to FAA officials, there is currently no standard for 
cabin ventilation rate, and it has yet to be determined if it is 
appropriate to compare building and aircraft ventilation rates because 
outside air at altitude is very clean, while air sources for buildings 
are often contaminated by pollution. Furthermore, in rare instances, 
oil leaks or other engine malfunctions can cause contaminants such as 
carbon monoxide to be released into the cabin ventilation system. The 
2001 Council report noted that questions about the frequency and 
significance of such incidents remain unanswered. In February 2002, FAA 
published a report that discussed many of the issues in the Council 
report, including an estimate of 416 air contaminant events (or 2.2 
events every 1,000,000 aircraft hours) that may have taken place in 
commercial transports within the United States between January 1978 and 
December 1999.

Figure 2: Overview of How Air Is Supplied on a Commercial Airliner:

[See PDF for image]

(1) Outside air continuously enters the engine, where it is compressed.

(2) It then passes through a catalytic ozone converter (in some 
aircraft) to air-conditioning packs.

(3) The air passes through cooling packs to a mixing manifold.

(4) Outside air entering the mixing manifold is mixed with recirculated 
air that has been cleaned with high-efficiency filters.

(5) The makeup of air in the mixing manifold is approximately 50 
percent outside and 50 percent filtered, recirculated air.

(6) Air from the mixing manifold is then supplied to the cabin on a 
continuous basis from overhead outlets.

(7) As outside air enters the airplane, air is continuously exhausted 
from the airplane.

(8) Mixed outside and filtered recirculated air is provided to the 
flight deck from the mixing manifold.

[End of figure]

FAA is responsible for setting design standards for aircraft 
ventilation systems. To fulfill its responsibilities, FAA requires that 
manufacturers design and build their large commercial airplanes to meet 
specific engineering standards, which limit the amounts of certain air 
quality contaminants (e.g., carbon monoxide, carbon dioxide, and ozone) 
that can be present in an airliner cabin. Manufacturers comply with 
these engineering standards in order to have FAA certify their 
airplanes as airworthy.[Footnote 13] However, while FAA monitors 
overall aircraft system operations, it does not require airlines to 
monitor cabin air quality during their operations to determine if air 
quality during routine flight operations is meeting the agency's 
engineering standards. According to FAA, the certification requirements 
combined with the monitoring of overall aircraft system operations are 
sufficient. However, the 2001 Council report stated that because of a 
lack of data it was not able to answer questions about the extent to 
which aircraft ventilation systems are operated properly.

Despite a Number of Studies, Data Are Lacking About the Effects of Air 
Quality On Cabin Occupants:

Passengers and flight attendants have had long-standing concerns about 
negative health effects from the quality of air in airliner cabins; 
however, research to date, including two reports by the Council, has 
not been able to definitively link the broad, nonspecific health 
complaints of passengers and flight attendants to possible causes, 
including cabin air quality. In its most recent report, the Council 
concluded that critical questions about the potential effect of cabin 
air quality on the health of cabin occupants remain unanswered because 
existing data are inadequate, and it recommended further research to 
narrow this knowledge gap.

Passengers and flight attendants (cabin occupants) have long complained 
of acute and chronic health effects during and after flying. Many 
complaints made by cabin occupants are relatively minor, such as dry 
eyes and nose, or the onset of colds soon after flying, but others are 
much more serious. According to the Association of Flight Attendants, 
its members have reported such health problems as respiratory diseases, 
nausea, dizziness, muscle tremors, nervous system damage, and memory 
loss.[Footnote 14] The association notes that these illnesses are 
consistent with exposure to carbon monoxide, pesticides, reduced oxygen 
levels, neurotoxins, and ozone gas, all of which can be present in the 
cabin itself or in cabin air supplies, depending on the flight. In 
addition, passengers with certain medical conditions can be at higher 
risk from the quality of cabin air than the general population due to 
air contaminants, lowered oxygen levels in the body (hypoxia), and 
changes in cabin pressure. Such medical conditions include limited lung 
capacity (e.g., asthma) and cardiovascular and circulatory disorders. 
Those who fly soon after surgery are particularly vulnerable to changes 
in cabin pressure. However, according to the Council report, many of 
the complaints made by cabin occupants are so broad and nonspecific 
that they could have many causes, and it is difficult to determine a 
specific illness or syndrome.

Although numerous studies have been conducted on cabin air quality 
issues, there are insufficient data to determine the nature and extent 
of cabin air quality's effect on cabin occupants. Council reports 
published in 1986 and 2001 reviewed the literature on cabin air quality 
issues and concluded that the studies had not collected data in a 
systematic manner that would conclusively address many of the questions 
about potential exposures in aircraft cabins and their health effects. 
Both reports recommended actions for improving what is known about 
cabin air quality, including the need to collect better data on the 
potential effect of cabin air quality on passenger and cabin crew 
health. The 2001 report concluded that available data on air quality 
and its possible negative effects on cabin occupant health have left 
three critical outstanding questions unaddressed and that additional 
research is needed:

* Do current aircraft as operated comply with FAA design and 
operational limits for ventilation rate and for chemical contaminants, 
including ozone, carbon monoxide, and carbon dioxide, and are the 
existing air quality regulations adequate to protect health and ensure 
the comfort of passengers and cabin crew?

* What is the association, if any, between exposure to cabin air 
contaminants and reports or observations of adverse health effects in 
cabin crew and passengers?

* What are the frequency and severity of incidents when air 
contaminants enter the cabin due to nonroutine conditions such as oil 
leaks or other engine malfunctions?

Following the 1986 report, the Department of Transportation sponsored a 
study to evaluate the health risks posed by exposures to contaminants 
on randomly selected flights. In addition, various researchers 
conducted a number of studies of cabin air quality issues, including 
eight investigations of biological agents, such as viruses and 
bacteria, on commercial aircraft. However, these and other studies were 
not able to link the broad, nonspecific health complaints that 
passengers and cabin crew continued to make to possible causes, 
including cabin air quality.

Recognizing the need for more data on the issue, Congress directed FAA, 
in AIR-21,[Footnote 15] to request that the Council perform another 
independent examination of cabin air quality. The Council's report, 
issued in 2001, concluded that when operated properly, the 
environmental control system[Footnote 16] should provide an ample 
supply of air to pressurize the cabin, meet general comfort conditions, 
and dilute or reduce normally occurring odors, heat, and contaminants. 
However, the Council also found that the design standard for 
ventilation rates[Footnote 17] in aircraft required by FAA was less 
than one-half to two-thirds the rate recommended by ASHRAE for 
buildings. The Council noted that whether the building ventilation 
standard is appropriate for the aircraft cabin environment has not been 
established.[Footnote 18] Studies have shown that low ventilation rates 
in buildings have contributed to "sick building syndrome," which causes 
fatigue, headache, and throat irritation. However, FAA officials told 
us that a sick building syndrome comparison is not applicable, in part 
because HEPA filtration results in much cleaner recirculated air than 
in a building environment.

The 2001 Council report also found that although the environmental 
control system in aircraft is designed to provide adequate air pressure 
and minimize the concentration of contaminants in the cabin, passengers 
and cabin crew are potentially exposed to air quality-related health 
risks. The Council was particularly concerned about two cabin air 
characteristics and suggested that they be given high priority for 
further investigation. The first is reduced oxygen partial pressure, 
which results from the lower air pressures present in aircraft cabins 
at cruise altitudes. Most healthy individuals are unaffected by reduced 
oxygen partial pressure, but those with health problems such as 
cardiopulmonary disease and infants can experience serious health 
effects from a lack of oxygen (e.g., respiratory stress). The other 
concern of the Council was elevated concentrations of ozone, which can 
occur at high cruise altitudes over certain areas of earth, such as the 
Arctic. The Council reported that unacceptably high ozone levels could 
occur in passenger cabins of commercial aircraft in the absence of 
effective controls. FAA allows aircraft operators to maintain cabin 
ozone concentrations at or below prescribed limits through flight 
planning that avoids areas with ozone concentrations exceeding those 
limits or the installation of devices that convert ozone to oxygen. 
However, FAA does not have a process in place to ensure that ozone 
converters are installed in all aircraft that fly routes where ozone 
may pose a risk or that converters in service are operating properly.

The Council also had what it termed moderate concern about several 
other potential air quality-related exposures on aircraft, but it noted 
that there were little data available on the frequency at which they 
occur. For example, according to the Council, infectious agents, such 
as viruses and bacteria, were likely present on aircraft, and high 
occupant densities could increase the risk of transmittal. The Council 
observed, however, that air recirculation did not increase the risk of 
transmittal, especially in systems using HEPA filters. Likewise, the 
Council noted that airborne allergens, such as cat dander, could pose 
problems for passengers with sensitivities. In addition, when aircraft 
are on the ground, according to the Council, passengers can be exposed 
to contaminants from engine exhaust, such as carbon monoxide and other 
outdoor air pollutants, including ozone and particulate matter, when 
they are pulled into the aircraft through the ventilation system. Also 
of some concern to the Council were incidents when lubricating and 
hydraulic fluids seep into the aircraft ventilation system during 
engine and other system malfunctions. Although such occurrences are 
rare, and the actual exposure to contaminants resulting from them is 
unknown, lubricating and hydraulic fluids contain substances that can 
pose neurological health risks to passengers and cabin crew if they are 
present in sufficient concentrations and for a sufficient length of 
time. Finally, the Council was somewhat concerned about exposures to 
the pesticide spraying that takes place on some international 
flights,[Footnote 19] which can cause skin rashes and other health 
effects. Table 1 summarizes information presented by the Council on the 
potential air quality-related exposures on aircraft.

Table 1: Potential Air Quality Related Concerns on Aircraft Cited by 
the National Research Council in 2001:

High concern: 

Characteristic: Cabin pressure: 

Potential health impacts: Serious health effects may occur in infants 
and those with cardio-respiratory diseases from lack of oxygen. 
Temporary discomfort or pain from gas expansion in middle ears or 
sinuses; 

Exposure frequency: Reduced cabin pressure occurs on nearly all 
flights; 

Availability of information: Reliable measurements are available; 
health effects in some sensitive groups are uncertain.

Characteristic: Ozone: 

Potential health impacts: Airway irritation and reduced lung function; 

Exposure frequency: Elevated concentrations are expected primarily on 
aircraft without ozone converters; 

Availability of information: Few systematic measurements made since 
1986 Council report.

Moderate concern: 

Characteristic: Airborne allergens: 

Potential health impacts: Irritated eyes and nose, sinusitis, acute 
increases of asthma, or anaphylaxis; 

Exposure frequency: Not known; 

Availability of information: Only self- reported data are available.

Characteristic: Carbon monoxide: 

Potential health impacts: Headaches and lightheadedness occur at low 
concentrations, more serious health effects result from higher 
concentrations; 

Exposure frequency: High concentrations could occur during air-quality 
incidents. Frequency of incidents is highly uncertain but is believed 
to be low; 

Availability of information: Reliable measurements are available for 
normal operating conditions, but no data are available for incidents.

Characteristic: Hydraulic fluids: 

Potential health impacts: Mild to severe health effects can result 
from exposure to these fluids; 

Exposure frequency: Frequency of incidents in which these fluids enter 
the cabin is uncertain but is expected to be relatively low; 

Availability of information: No quantitative data are available. 
Little information is available on health effects related to smoke, 
mists, or odors in aircraft cabins.

Characteristic: Pesticides: 

Potential health impacts: Skin rashes can result from skin or 
inhalation exposure; 

Exposure frequency: Exposure likely on some international flights; 

Availability of information: Only self-reported data are available.

Low Concern: 

Characteristic: Carbon dioxide: 

Potential health impacts: Indicator of ventilation adequacy. Elevated 
concentrations associated with increased perceptions of poor air 
quality; 

Exposure frequency: Concentrations are generally below FAA regulatory 
limits; 

Availability of information: Reliable measurements are available only 
for normal operating conditions.

Characteristic: Nuisance odors: 

Potential health impacts: Annoyance and mucous membrane irritation can 
occur; 

Exposure frequency: Can be present on any flight; 

Availability of information: Reliable information is available from 
surveys of cabin occupants.

Characteristic: Relative humidity: 

Potential health impacts: Temporary drying of skin, eyes, and mucous 
membranes can occur at relative low humidity (10 to 20%); 

Exposure frequency: Relative low humidity occurs on most flights; 

Availability of information: Reliable and accurate measurements in 
aircraft are available. 

Source: National Research Council.

[End of table]

Since the issuance of the 2001 Council report, some limited studies 
have examined specific air quality issues, such as infectious disease 
transmission, but they have raised as many questions as they have 
answered. For example, according to a revised 2003 WHO report on 
tuberculosis (TB) and air travel, as of August 2003, no case of active 
TB has been identified as resulting from exposure while on a commercial 
aircraft.[Footnote 20] The report did note, however, that there is some 
evidence that transmission of TB may occur during long flights (i.e., 
more than 8 hours) from an infectious source (passenger or crew) to 
other passengers or crewmembers. In 2002, the American Medical 
Association[Footnote 21] did not find any evidence that aircraft cabin 
air recirculation increases the risk for upper respiratory tract 
infection (URI) symptoms in passengers traveling aboard commercial 
jets. However, passengers had higher incidents of URI infections than 
the general public within a week after completing their trips. One of 
the study's authors noted that the research indicated that while flying 
increases the risk of getting colds or other infections, an aircraft's 
ventilation system may not be a key factor. A 2003 study appearing in 
the New England Journal of Medicine found that SARS transmissions may 
occur on flights carrying people in the symptomatic stages of the 
disease. (See app. II for more details on this study.[Footnote 22]):

FAA has Taken Action to Address Council Recommendations On Cabin Air 
Quality, but These Efforts Could Be Improved:

The December 2001 Council report on airliner cabin air quality made 10 
recommendations about air quality standards for the cabins of 
commercial airliners and the need for more information concerning the 
health effects of cabin air. Nine of these recommendations were 
directed to FAA, and it has implemented them to varying degrees. The 
Council report's 10 recommendations focused on five aspects of cabin 
air quality and its environment: (1) the establishment of cabin air 
quality surveillance and research programs, (2) FAA's oversight of the 
operation of aircraft ventilation systems, (3) exposures on aircraft 
due to the transport of small animals in aircraft cabins, (4) 
distribution of health related information, and (5) recommended 
procedures as a result of a ventilation system shutdown. Although one 
recommendation asked Congress to designate a lead federal agency for 
conducting airliner cabin air quality research, most of the 
recommendations were directed at or involved FAA. Table 2 describes 
each of the Council report recommendations and FAA's response.

Table 2: Status of the National Research Council's 2001 Report 
Recommendations on Airliner Cabin Air Quality:

Cabin Air Quality Surveillance and Research Request: 

Council Report Recommendations: Surveillance program; To be consistent 
with FAA's mission to promote aviation safety, an air quality and 
health- surveillance program should be established. The objectives and 
approaches of this program are summarized in appendix V of this 
report. The health and air quality components should be coordinated so 
that the data are collected in a manner that allows analysis of the 
suggested relationship between health effects or complaints and cabin 
air quality; FAA's Response: FAA is addressing this recommendation 
through a joint research effort combining the resources of FAA and the 
American Society of Heating, Refrigerating and Air-Conditioning 
Engineers (ASHRAE).

Council Report Recommendations: Research program; To answer specific 
questions about cabin air quality, a research program should be 
established. See appendix V of this report for a summary of research 
questions, objectives, and research program approach; FAA's Response: 
FAA is addressing this recommendation through a joint research effort 
combining the resources of FAA and ASHRAE.

Council Report Recommendations: Research program lead agency; The 
Council committee recommends that Congress designate a lead federal 
agency and provide sufficient funds to conduct or direct the research 
program recommendation (see above), which is aimed at filling major 
knowledge gaps identified in this report. An independent advisory 
committee with appropriate scientific, medical, and engineering 
expertise should be formed to oversee the research program to ensure 
that its objectives are met and the results publicly disseminated; 
FAA's Response: Congress has designated FAA as the lead agency to 
direct the cabin air quality research program, but, according to FAA 
officials, has not appropriated sufficient funds to support it.

FAA Oversight of Aircraft Ventilation Systems: 

Council Report Recommendations: Air quality regulations; FAA should 
rigorously demonstrate in public reports the adequacy of current and 
proposed Federal Aviation Regulations (FARs) related to cabin air 
quality and should provide quantitative evidence and rationales to 
support sections of the regulations that establish air quality-related 
design and operational standards for aircraft (standards for carbon 
monoxide, carbon dioxide, ozone, ventilation, and cabin pressure). If 
a specific standard is found to be inadequate to protect the health 
and ensure the comfort of passengers and crew, FAA should revise it. 
For ventilation, the committee recommends that an operational standard 
consistent with the design standard be established; FAA's Response: 
Necessary data to implement this recommendation will be available upon 
completion of the ASHRAE study in late 2006 or early 2007.

Council Report Recommendations: Regulations for ozone; FAA should take 
effective measures to ensure that the current FAR for ozone (average 
concentrations not to exceed 0.1 ppm above 27,000 ft; and peak 
concentrations not to exceed 0.25 ppm above 32,000 ft.) is met on all 
flights, regardless of altitude. These measures should include a 
requirement that either ozone converters be installed, used, and 
maintained on all aircraft capable of flying at or above those 
altitudes, or strict operating limits be set with regard to altitudes 
and routes for aircraft without converters to ensure that the ozone 
concentrations are not exceeded in reasonable worst-case scenarios. To 
ensure compliance with the ozone requirements, FAA should conduct 
monitoring to verify that the ozone controls are operating properly 
(see also surveillance program recommendation); FAA's Response: 
Necessary data to implement this recommendation will be available upon 
completion of the ASHRAE study.

Council Report Recommendations: Air cleaning equipment; FAA should 
investigate and publicly report on the need for and feasibility of 
installing air cleaning equipment for removing particles and vapors 
from the air supplied by the environmental control system (ECS) on all 
aircraft to prevent or minimize the introduction of contaminants into 
the passenger cabin during ground operation, normal flight, and air 
quality incidents; FAA's Response: Necessary data to implement this 
recommendation will be available upon completion of the ASHRAE study.

Council Report Recommendations: Carbon monoxide monitoring; FAA should 
require a carbon monoxide monitor in the air supply ducts to passenger 
cabins and establish standard operating procedures for responding to 
elevated carbon monoxide concentrations; FAA's Response: Necessary 
data to implement this recommendation will be available upon 
completion of the ASHRAE study.

Exposures on Aircraft, Health Information, and Ventilation Shutdown 
Procedures: 

Council Report Recommendations: Allergens; Because of the potential 
for serious health effects related to exposures of sensitive people to 
allergens, the need to prohibit transport of small animals in aircraft
cabins should be investigated, and cabin crews should be trained to 
recognize and respond to severe, potentially life-threatening 
responses (e.g., anaphylaxis, severe asthma attacks) that 
hypersensitive people might experience because of exposure to airborne 
allergens; FAA's Response: FAA issued an advisory circular providing 
guidance regarding air carrier passenger handling procedures for 
allergen-sensitive people, but did not prohibit the transport of 
animals on aircraft, particularly service animals. Agency officials do 
not think that a prohibition on animals in the cabin would be 
effective in minimizing animal allergens because they believe that 
these allergens are brought on board aircraft primarily on the clothes 
of passengers.

Council Report Recommendations: Health information; Increased efforts 
should be made to provide cabin crew, passengers, and health 
professionals with information on health issues related to air travel. 
To that end, FAA and the airlines should work with such organizations 
as the American Medical Association and the Aerospace Medical 
Association to improve health professionals' awareness of the need to 
advise patients on the potential risks of flying, including risks 
associated with decreased cabin pressure, flying with active 
infections, increased susceptibility to infection, or hypersensitivity; FAA's Response: The FAA's Office of Aerospace Medicine made health information and recommendations available to passengers and crews through its Web site and linked the site to other health-related organizations. The agency also developed a brochure on the potential risk of developing a condition known as deep vein thrombosis (DVT), in which blood clots can develop deep in the veins of the legs after extended periods of inactivity. This brochure has been distributed to aviation medical examiners and cited in the Federal Air Surgeon's Bulletin.

Council Report Recommendations: Ventilation shutdown; The committee 
reiterates the recommendation of the 1986 Council report that a 
regulation be established to require removal of passengers from an 
aircraft within 30 minutes after a ventilation failure or shutdown on 
the ground and ensure the maintenance of full ventilation whenever on-
board or ground- based air conditioning is available; FAA's Response: 
FAA concurred with the objective of the recommendation and advised air 
carriers, through advisory circulars, to deplane passengers as long as 
operational safety is not compromised. 

Sources: National Research Council and GAO analysis of FAA documents.

Note: Federal Aviation Regulations are legal requirements and rules for 
the aviation industry set by the Federal Aviation Administration.

[End of table]

FAA formed the Airliner Cabin Environment Report Response Team to 
review the findings of the NRC report on airliner cabin air quality and 
published a planned response in February 2002. However, many of the 
actions included in this plan were contingent on the formation of an 
aviation rulemaking advisory committee, on which the agency has 
deferred action. FAA subsequently updated its plans, as reflected 
above.

We reviewed FAA's approach for addressing the recommendations and found 
that the agency has made progress on implementing some of them, 
including those relating to making information available on potential 
health issues related to cabin air quality and the risks posed to 
sensitive people by allergens from small animals transported in 
aircraft cabins; however action on others is pending. For example, 
recommendations to improve FAA oversight of aircraft ventilation 
systems are pending until completion of the ASHRAE study in late 2006 
or early 2007. In implementing the Council report recommendations, FAA 
is attempting to balance the need to conduct additional research on the 
healthfulness of cabin air quality with other research priorities, such 
as improving passenger safety. Our prior work on airliner cabin safety 
and health has underscored the importance of setting risk-based 
research priorities, in part by establishing cost and effectiveness 
estimates to allow direct comparisons among competing research 
priorities. In commenting on this prior work, FAA cautioned that if too 
much emphasis is placed on cost/benefit analyses, potentially valuable 
research may not be undertaken.[Footnote 23] We concur in that caution. 
Similarly, we found that many members of the Council committee on 
airliner cabin air quality question FAA's approach to implementing some 
of the recommendations it made, particularly those related to the 
committee's principal finding that more comprehensive research on the 
health effects of cabin air quality is needed. Specifically, some in 
the aviation community have raised concerns that FAA's planned actions 
for implementing the Council recommendations on cabin air quality, 
including its research and surveillance efforts, will not be adequate 
to answer long-standing questions about the nature and extent of 
potential health effects posed by cabin air.

Council Recommendations Calling for Cabin Air Quality Surveillance and 
Research Programs:

To address the need for more information on the health effects of cabin 
air quality, the 2001 Council report made three recommendations 
regarding the establishment of cabin air quality surveillance and 
research programs. FAA, in coordination with ASHRAE, has begun to 
develop a program to monitor air quality on some flights and correlate 
this information with health data collected from passengers and cabin 
crews. Although this effort can provide a foundation for future 
research, members of the committee that produced the report are 
concerned that its scope is too limited to adequately answer long-
standing questions concerning the association between cabin air quality 
and health effects.

Council Concluded That Surveillance and Research Programs Needed to 
Answer Outstanding Questions Concerning Cabin Air Quality:

According to a committee member, the Council report's most important 
recommendations are those pertaining to the establishment of cabin air 
quality surveillance and research programs. The report concluded that 
available air quality data are not adequate to address three critical 
questions on aircraft cabin air quality and its possible effects on 
cabin occupant health:

* Do current aircraft, as operated, comply with FAA design and 
operational limits for ventilation rate and for chemical contaminants, 
including ozone, carbon monoxide, and carbon dioxide, and are the 
existing air quality regulations adequate to protect the health and 
ensure the comfort of passengers and the cabin crew?

* What is the association, if any, between exposure to cabin air 
contaminants and reports or observations of adverse health effects in 
cabin crew and passengers?

* What are the frequency and severity of incidents when air 
contaminants enter the cabin due to nonroutine conditions such as oil 
leaks or other engine malfunctions?

To answer these questions, the Council report recommended a dual 
approach that includes a routine surveillance program and a more 
focused research program. The report said that the surveillance program 
should continuously monitor and record chemical contaminants, cabin 
pressure, temperature, and relative humidity in a representative number 
of flights over a period of 1 to 2 years. Thereafter, the program 
should continue to monitor flights to ensure accurate characterization 
of air quality as existing aircraft equipment ages or is upgraded. In 
addition to air quality monitoring, the report said the surveillance 
program should also include the systematic collection, analysis, and 
reporting of health data, with the cabin crew as the primary study 
group. The report said a detailed research program to investigate 
specific questions about the possible association between air 
contaminants and reported health effects should supplement the 
surveillance program. Among the subjects suggested for research are the 
factors that affect ozone concentration in cabin air and the adequacy 
of outside air ventilation flow rates.

FAA Has Taken the Lead in Developing Surveillance and Research 
Programs:

In order to implement the surveillance and research programs, the 
report recommended that Congress designate a lead federal agency and 
provide sufficient funding to conduct or direct the research program to 
fill the major knowledge gaps. It also called for an independent 
advisory committee with appropriate scientific, medical, and 
engineering expertise to oversee the programs to ensure that the 
research program's objectives are met. In response, as a part of FAA's 
reauthorization, Congress designated FAA as the lead federal 
agency.[Footnote 24] Prior to this, FAA acted in this capacity and 
allocated limited funding for this effort, although, according to FAA 
officials, Congress provided no additional funding through fiscal year 
2003 for air quality surveillance and research; however, pending 
legislation for fiscal year 2004 would provide $2.5 million for this 
effort. In addition, on March 4, 2003, FAA announced the creation of a 
voluntary program for air carriers, called the Aviation Safety and 
Health Partnership Program. Through this program, the agency intends to 
enter into partnership agreements with participating air carriers, 
which will, at a minimum, make data on their employees' injuries and 
illnesses available to FAA for collection and analysis. According to 
FAA officials, this program has a reporting system and database 
available to capture air quality incidents.

In taking the lead for implementing the recommendations for 
surveillance and research programs, FAA has undertaken a joint effort 
with ASHRAE. According to FAA, this joint effort will build on a 
previous study conducted for FAA by NIOSH, which identified and 
characterized potential health issues, including respiratory effects, 
related to the aircraft cabin environment, but did not link the health 
issues to cabin conditions.[Footnote 25] The joint effort includes a 
surveillance and research initiative whose principal aim is to relate 
perceptions of discomfort or health-related symptoms that flight 
attendants and passengers have had to possible causal factors, 
including cabin and outside air quality and other factors, such as 
reduced air pressure, jet lag, inactivity, humidity, flight attendant 
duty schedule and fatigue, disruptions to circadian rhythm,[Footnote 
26] stress, and noise. While FAA's fiscal year 2004 appropriation in 
the research and development budget includes $2.5 million for cabin air 
research--including identifying bacterial and pesticide contamination 
and monitoring air quality incidents--it is unclear which of the cabin 
air quality projects outlined in the FAA reauthorization bill will be 
funded.[Footnote 27] Additionally, ASHRAE officials stated that the 
surveillance and research initiative would support ASHRAE's ongoing 
efforts to develop air quality standards for commercial aircraft.

According to FAA, the surveillance and research program is to be 
carried out in two parts; the first started in December 2003 and the 
second will start in December 2004 and end in late 2006 or early 2007. 
In part I, air quality data will be collected on four to six flights on 
a minimum of two different types of aircraft, and the data will then be 
compared with health information gathered from surveys of passengers 
and crew on the flights. According to FAA and ASHRAE, the protocol and 
procedures developed in part I of the study will be the basis for 
conducting on-ground and in-flight monitoring in part II of the 
initiative. In part II, air quality monitoring will be conducted on 
different models of commercial jet airplanes representing a large 
section of the world fleet and will include a minimum number of flights 
that has not yet been determined.[Footnote 28] However, according to 
FAA officials, the level of funding that will be available for part II 
is uncertain. FAA and ASHRAE have assembled a committee which is 
responsible for selecting a contractor to conduct the monitoring and 
health surveillance in part I and overseeing the contractor's 
performance. The committee consists of aircraft, health, and air 
quality experts, including five members of the Council committee, as 
well as representatives from FAA, the Association of Professional 
Flight Attendants, and the Boeing Commercial Airplane Group. In 
September 2003, the committee chose a contractor for part I, and work 
began in December 2003. FAA and ASHRAE have not yet selected a 
contractor for part II, although the estimated completion date for the 
entire program is late 2006 or early 2007.

ASHRAE officials stated that to date FAA, Boeing, and two major U.S. 
airlines are supporting this effort. FAA has provided $50,000 of the 
estimated $250,000 it will cost to conduct air quality surveillance on 
two aircraft. Boeing is the major source for the balance of the funding 
for the surveillance program. FAA had previously reported that it was 
seeking a $500,000 contract with the Johns Hopkins University Applied 
Physics Laboratory (APL) to develop devices to monitor the aircraft 
cabin environment as part of the research and surveillance program. 
However, the contract was not finalized because APL determined that the 
project would cost significantly more than $500,000 and FAA 
reprogrammed the funds. FAA said that it has not yet funded part II, 
while ASHRAE officials noted that they are planning to solicit the part 
I contributors again for part II once part I is under way.

Despite FAA's efforts to date, we found that the agency has not 
developed a detailed plan for the research and surveillance program, 
including key milestones and funding estimates, in keeping with 
generally accepted practices for oversight and independence. In 
addition, the agency has not created an independent panel of experts in 
the areas of aircraft ventilation, air quality, and public health to 
help plan and oversee this effort. Furthermore, FAA's plans do not 
explicitly include leveraging the findings of international research on 
cabin air quality.

Committee Members Concerned about Scope, Independence, and Funding of 
FAA Surveillance and Research Program:

Members of the committee that produced the 2001 Council report are 
concerned that the FAA/ASHRAE surveillance and research program, as 
designed, will fall short of answering the long-standing questions 
about the effect of cabin air quality on passenger and cabin crew 
health and comfort. We contacted the 13 members of the committee, and 8 
agreed to comment on FAA's response to their recommendations on cabin 
air quality surveillance and research. We refer to these 8 individuals 
from here forward as commenting committee members. Although 5 of 8 
commenting committee members said that the initiative should shed some 
light on cabin air quality's effects on health, all said that it was 
much more limited than the committee had envisioned. Two of the 8 
commenting committee members thought that the air quality and health 
surveillance initiative should be a continuous undertaking in which air 
quality and health information is taken from a representative sample of 
commercial aircraft and flight routes. They also said that it appears 
the FAA and ASHRAE program will not include a broad enough cross-
section of aircraft and flights to determine the full range of air 
quality problems and relate them to health effects. Two commenting 
committee members said that part I of the FAA and ASHRAE program will 
extensively monitor cabin air quality on two aircraft types; however, 
part I will not provide information that is generalizable to the U.S. 
commercial airliner fleet. According to Boeing officials involved in 
this study, part I research is designed to validate test equipment and 
study protocols and is not designed to be generalized to the airliner 
fleet. One committee member said that although more aircraft are to be 
included in part II, it is doubtful that enough information will be 
collected to adequately answer the key questions the agency's research 
and surveillance program was designed to address. According to Boeing 
officials, part II includes plans for information collection to address 
the key question of the agency surveillance and research program, 
provided sufficient funds are available. Another commenting committee 
member said that the FAA and ASHRAE program would also yield little or 
no information on air quality incidents that occur when cabin air is 
contaminated by oil or hydraulic fuel leaks. According to the member, 
these incidents are rare and can be monitored only if simple, 
inexpensive equipment (e.g., devices that can "grab" samples) is 
available to cabin crew on a large number of flights to use in the 
event that an incident occurs. FAA officials said that issues of 
sampling adequacy and specimen handling could complicate the grab 
sample approach. These officials also noted that a voluntary injury and 
illness reporting system that it has in place could capture air quality 
incidents if it were made mandatory.

Seven of the eight commenting committee members also noted that FAA has 
not adequately addressed the Council report's recommendations regarding 
cabin air surveillance and research programs. FAA has indicated that 
its program responds to the report's recommendations calling for 
surveillance and research efforts. However, these committee members 
believe that the program focuses only on surveillance and does not 
include in-depth research of air quality issues as outlined in the 
committee's recommendation calling for a separate comprehensive 
research program.

One of the commenting committee members said that a cabin air quality 
study currently under way in Europe contains many of the elements that 
the committee had hoped to see in the U.S. surveillance and research 
efforts. As part of the ongoing surveillance and research study, the 
European cabin air study[Footnote 29] is currently coordinated by 
Building Research Establishment, Ltd. (BRE).[Footnote 30] The study 
focuses on three major goals: (1) advancing the industry's 
understanding of what is known about air quality issues by assessing 
the current level of air quality found in aircraft cabins; (2) 
identifying the technology (i.e., environmental control systems 
including filtration and air distribution) that is available to improve 
cabin air quality; and (3) assessing and determining potential 
improvements to existing standards and performance specifications for 
the cabin environment. (The scope and methodology for Europe's cabin 
air study is found in appendix IV). The cabin air study partnered (to 
various degrees) with 16 organizations, including Boeing, Airbus 
Deutschland, Honeywell (manufacturer of environmental control 
systems), Pall Aerospace (filter manufacturer), British Airways, United 
Kingdom's Civil Aviation Authority (CAA), European Joint Aviation 
Authorities (JAA), and other organizations representing Austria, 
France, Germany, Greece, Norway, Poland, and Sweden. The European cabin 
air study began on January 2001 with an estimated cost of $8 million 
and is expected to disclose its findings in 2004.[Footnote 31]

Of the eight commenting committee members, three addressed the funding 
of the FAA and ASHRAE surveillance and research programs. These members 
said that the amount of funding available for U.S. efforts might be 
insufficient to conduct surveillance and research programs of the scope 
they envisioned in their recommendations. For example, one of the 
committee members stated that to conduct a surveillance and research 
program of the scope the Council had in mind, Congress would have to 
provide funding levels comparable to that of the European cabin air 
study.

One commenting committee member, National Institute for Occupational 
Safety and Health (NIOSH) officials, and airline flight attendant 
representatives we interviewed expressed concern that the extensive 
involvement of aircraft manufacturers and airlines in the design and 
implementation of the FAA and ASHRAE program could threaten the 
independence of the effort. However, with the exception of the flight 
attendant representatives,[Footnote 32] they agreed that any 
surveillance and research programs require participation by these 
groups. Nonetheless, they point to the fact that much of the available 
funding for the initiative ($200,000 of the $250,000) is coming from 
the aviation industry, which has a stake in the outcome, and that this 
might give the impression that the study lacks the necessary 
objectivity. The commenting committee member suggested that the 
research money provided by the aviation industry be placed in a special 
fund that would be managed by FAA or an independent research group. 
According to ATA officials, due to a lack of public funding on a scale 
comparable to what has been provided for Europe's cabin air study, the 
financial support and cooperation of aircraft manufacturers and 
airlines is essential if FAA is to conduct this research. In addition, 
Boeing officials stressed that the project funding is currently 
controlled by ASHRAE and the project oversight committee is led by the 
chairman of the Council study.

Five of the commenting committee members also discussed the status of 
their recommendation concerning the need for Congress to designate a 
lead federal agency and advisory committee for the air quality research 
effort. Although Congress designated FAA as the lead agency in November 
2003, FAA had already assumed responsibility for implementing the 
research and surveillance-related recommendations. In commenting on the 
Council recommendation to designate a lead federal agency, several 
members said they thought that the lead agency should be one that is 
experienced in conducting scientific research on air quality and 
environmental health issues. Some noted that the Environmental 
Protection Agency (EPA) has supported a large body of research into air 
quality issues, and another pointed out that NIOSH has performed 
studies of air quality in buildings and the workplace. Several 
commenting members indicated that although it is FAA's mission to 
promote aviation safety, they had reservations about whether the agency 
was well suited to oversee a large air quality research program on its 
own. Several members thought that, as an alternative, FAA might be part 
of a cooperative federal effort to perform airliner cabin air quality 
research. In addition, another committee member believes that although 
FAA has a committee to oversee the selection of the contractor for the 
program, it has not assembled an advisory committee to review the 
research design and monitor the implementation of the program.

Council's Recommendations Concerning FAA Oversight of Aircraft 
Ventilation Systems:

Four of the Council recommendations pertain to FAA's oversight of the 
operation of aircraft ventilation systems. These recommendations call 
for FAA to (1) demonstrate in public reports the adequacy of its 
regulations related to cabin air quality and establish operational 
standards for ventilation systems, (2) ensure that standards for ozone 
levels are met on all flights, (3) investigate the need for and 
feasibility of installing equipment to clean the air supplied to 
aircraft ventilation systems, and 4) require carbon monoxide monitors 
in air supply ducts to passenger cabins and establish procedures for 
dealing with elevated carbon monoxide concentrations. According to FAA 
officials, the agency originally planned to have an aviation rulemaking 
advisory committee assess whether current standards were appropriate 
for ensuring that aircraft ventilation systems adequately prevent 
contamination of cabin air. However, FAA decided to defer this action 
until data is available from the surveillance and research study, as 
well as the European cabin air study. Additionally, FAA believes that 
data from this study will aid in the reconsideration of air quality 
standards for commercial aircraft. However, most of the commenting 
committee members questioned the need for delay in addressing some of 
the recommendations.

Four of the eight commenting committee members said that they 
recommended that FAA demonstrate, in public records, the rationale for 
the established design standards for carbon monoxide (CO), carbon 
dioxide (CO2), ozone (O3), ventilation, and cabin pressure because FAA 
was unable to explain the reasoning for these standards. For example, 
FAA has not documented the reasons for setting the ventilation rate 
standard for aircraft cabins of new aircraft types at .55 pounds of 
outside air per minute per occupant. The American Society of Heating, 
Refrigerating and Air-Conditioning Engineers (ASHRAE)[Footnote 33] 
recommends that ventilation rates inside a building environment be at 
least 1.1 pounds of outside air per minute per occupant, which is about 
50 percent more than the current FAA requirement for aircraft. In 
addition, FAA has not documented the reasons for requiring a design for 
cabin air pressure altitude of not more than 8,000 feet air pressure, 
which is about three-fourths of the air pressure found at sea level. 
Members of the research community, including the Aerospace Medical 
Association (AsMA) and CAA, state that the loss of air pressure and 
oxygen may pose serious health risks for infants whose lungs have not 
fully developed and for older adults who may have upper respiratory 
problems.

In response to the committee members' comments, FAA provided us the 
following explanations for the design standards in question. The 
ventilation rate standard was based on a regulatory value established 
decades ago, which has been shown to be acceptable, and ASHRAE has 
formed a subcommittee to develop a standard specifically for airplanes. 
The limit for carbon monoxide concentration of 1 part in 20,000 parts 
air (0.005 percent) was adopted from the Occupational Safety and Health 
Administration (OSHA) and ASHRAE standards. The limit of maximum 
allowable carbon dioxide concentration in occupied areas of transport 
category airplanes was reduced to 0.5 percent in part due to a 
recommendation from the National Academy of Sciences to review the 
carbon dioxide limit in airplane cabins; it provides a cabin carbon 
dioxide concentration level representative of that recommended by some 
authorities for buildings. The ozone limits were based on studies 
conducted by the FAA Civil Aerospace Medical Institute and are 
comparable to standards adopted by the Environmental Protection Agency 
and the Occupational Safety and Health Administration. The cabin 
pressure altitude standard was based on the accepted industry practice 
of maintaining the health and safety of occupants while considering the 
structural limitations of the aircraft.

A commenting committee member also expressed concern that FAA certifies 
aircraft ventilation systems that are designed to meet certain 
standards, such as those for ventilation rates, but it does not require 
that systems operate in accordance with these standards. The practical 
effect is that aircraft are not monitored to determine if they meet the 
design standards. According to another commenting committee member, FAA 
did not need data from the planned research project to provide a 
rationale for ventilation system standards, or to require that 
ventilation systems operate according to standards. Some committee 
members also said that FAA could begin to take steps to ensure that 
ozone standards are met on all flights regardless of altitude and 
require monitors for dangerous carbon monoxide vapors in air supply 
ducts to passenger cabins before the completion of the planned research 
study. FAA officials said that although it does not conduct recurrent 
system design compliance checks, the agency uses various reporting 
systems to monitor aircraft system performance and takes appropriate 
mandatory action when an unsafe condition is found.

Council Recommendation Concerning Airborne Allergens:

Because of the potential for serious health effects for people 
sensitive to allergens, the 2001 Council report also recommended that 
FAA investigate the need to prohibit the transport of small animals in 
aircraft cabins and provide training to cabin crews to deal with 
allergic reactions. However, FAA does not think that prohibiting 
animals in the cabin would be effective because it believes that most 
animal allergens are brought onboard aircraft on the clothes of 
passengers rather than by the animals themselves. Instead, the agency 
issued an advisory circular highlighting the effective procedures that 
passengers can use when carrying animals and guidance on how to train 
crewmembers to recognize and respond to in-flight medical events that 
result from exposure to allergens. Additionally, FAA will enhance its 
Internet site to provide general information related to FAA and air 
carrier policy concerning the transport of animals in aircraft cabins. 
Commenting committee members generally supported FAA's approach to this 
recommendation.

Council Recommendation Concerning Health Information:

In response to the Council report recommendation calling for FAA to 
increase efforts to provide cabin crew, passengers, and health 
professionals with information on health issues related to air travel, 
FAA modified the general information section of its Web site; however, 
we found that the traveler health information is not easy to access. 
FAA created hyperlinks to other Web sites, such as those of the 
Aerospace Medical Association and Centers for Disease Control and 
Prevention, which include information on potential health risks of 
flying, particularly for health-challenged individuals. However, we 
found it difficult to locate the section of the FAA Web site that deals 
with traveler health information and when we did, it required several 
steps to reach the hyperlinks. Some commenting committee members also 
noted how difficult it is to access health-related information on the 
FAA Web site. In addition to citing the need for FAA to increase the 
accessibility of health-related information on its Web site, six of the 
eight committee members also mentioned that FAA should take further 
steps to make health information available to the flying public. 
Suggestions included having airlines include health related information 
on their Web sites and establishing a program to provide flying-related 
heath risk information to physicians that they could then share with 
their patients (e.g., through brochures).

Council Recommendation Concerning Aircraft Ventilation System 
Shutdown:

FAA responded to the 2001 Council report recommendation that it 
establish a regulation to require removal of passengers from an 
aircraft within 30 minutes after a ventilation failure or shutdown on 
the ground by issuing an advisory circular to airlines. Some commenting 
committee members viewed this action as insufficient. This 
recommendation reiterated one made in the 1986 Council report, which 
FAA did not act on. The committees that produced both the 1986 and 2001 
reports noted that environmental conditions in an aircraft cabin 
respond quickly to changes in ventilation system operation. The 
committees felt that the ventilation system should not be shut down for 
a long period when the aircraft is occupied, except in the case of an 
emergency, because excessive contaminant concentrations and 
uncomfortably high temperatures can occur quickly. Several commenting 
committee members told us that they felt strongly that FAA should 
require passenger removal in the event of ventilation system shutdown 
of more than 30 minutes and that advising airlines that this should be 
done was insufficient to accomplish the committee's objective. FAA, on 
the other hand, said that airlines pay close attention to advisories. 
The agency decided against issuing a regulation because there are 
situations when an evacuation within 30 minutes is not possible due to 
operational necessity, such as when a ventilation system breakdown 
occurs on a taxiway far from a gate.

Some Technologies Exist for Improving Cabin Air Quality, but There Are 
Questions About Whether They Should be Required:

Several technologies exist today that could improve cabin air quality, 
but opinions vary on whether requiring the use of improved technologies 
in commercial airliner cabins is warranted. We found one of these 
technologies, HEPA filters, is strongly endorsed by cabin air quality 
and health experts as providing the best possible protection against 
one cabin air problem--the presence of particulates, bacteria, and 
viruses in recirculated air. While FAA does not currently require HEPA 
filters, some health experts believe these filters should be required, 
given their demonstrated effectiveness in cleansing cabin air. Figure 3 
illustrates a typical HEPA filter for commercial passenger aircraft.

Figure 3: A Typical HEPA Filter for Commercial Passenger Aircraft:

[See PDF for image]

[End of figure]

According to many in the aviation community, several technologies are 
available today, and more are in the planning stages, that could 
improve the air quality in commercial airliner cabins. However, some in 
the aviation industry question whether requiring their use is 
warranted. Filtering particulates, bacteria, viruses, and gaseous 
pollutants and removing ozone can improve the healthfulness of cabin 
air, and increasing cabin humidity and absorbing more cabin odors and 
gasses can increase the comfort of passengers and cabin crews. While 
aircraft manufacturers acknowledge that a few technologies are 
available today that could further improve air quality and comfort in 
airliner cabins and that more are possible in the future, they believe 
that unless future research proves otherwise, the ventilation systems 
in the aircraft they have produced provide ample amounts of relatively 
clean air. One technology with proven effectiveness is HEPA filtering 
of recycled cabin air. All new large commercial airliners in production 
with ventilation systems that recirculate cabin air come equipped with 
these filters, which, when properly fitted and maintained, are 
effective at capturing airborne contaminants such as viruses that enter 
the re-circulation system. However, some regional jets, which have 
fewer than 100 seats, are not equipped with filters, and some older 
large aircraft still use less efficient filters. FAA does not require 
the filtration of recirculated air, but health experts and members of 
the committee that produced the 2001 report on cabin air quality 
believe that given their proven effectiveness, HEPA filters should be 
required for all aircraft that recirculate cabin air. In addition, 
airflow rates could be increased in some aircraft by adjusting settings 
on the ventilation system, thereby dissipating the effects of some 
contaminants. However, this would be done at the expense of higher fuel 
consumption, increased engine emissions, and lower cabin humidity.

High Efficiency Particulate Filters Are an Effective Technology for 
Cleaning Recirculated Air:

HEPA filters are a readily available and affordable technology for 
providing the best possible protection against one cabin air problem--
the presence of particulates, bacteria, and viruses in recirculated 
air. However, HEPA filters will not filter gaseous contaminants. These 
filters have become widely available for aircraft since the late 1990s. 
According to EPA, HEPA filters can remove nearly all particulate 
contaminants, such as airborne particles and infectious agents 
including bacteria and viruses, from the recirculated air that passes 
through them.[Footnote 34] A manufacturer of HEPA filters, as well as 
health authorities such as CDC, NIOSH, and WHO, believe that HEPA 
filters are highly effective in preventing the transmission of bacteria 
and viruses through aircraft ventilation systems. However, they 
emphasize that HEPA filters clean only the air that is recirculated 
through aircraft ventilation systems, so transmissions from an infected 
person to others nearby are still possible.

HEPA filters are available for most large commercial airliners in the 
U.S. fleet, but some aircraft with recirculation systems are equipped 
with less effective filters. However, not all commercial aircraft 
recirculate air through their ventilation systems. For example, some 
smaller jets, such as the Boeing 717 and Bombardier CRJ-200s, which 
typically fly shorter routes, as well as older models of some longer-
range aircraft, such as the Boeing 737-200 and the DC-10, provide 100 
percent outside air to the passenger cabins instead of recirculating 
air and, therefore, would not need HEPA filters. Nevertheless, most 
commercial airliners in use today recirculate between 30 and 55 percent 
of the air provided to the passenger cabin. Officials from Boeing and 
Airbus, the world's two largest manufacturers of commercial aircraft, 
told us that all their aircraft with recirculation systems currently in 
production are equipped with HEPA filters. The ventilation systems in 
many older commercial aircraft were designed to use the less effective 
filters available at the time, and some of these aircraft still use 
these types of filters. However, according to Boeing and Airbus 
officials, HEPA filters can be used on these older aircraft with little 
or no retrofitting required.[Footnote 35] According to a filter 
manufacturer, a HEPA filter costs about twice as much (e.g., $400 to 
$600 for the smaller narrow-body aircraft) as the non-HEPA models that 
are less effective in trapping particulates. Some regional jets, such 
as the Embraer ERJ-145 recirculate air but are not equipped with 
filters.

In fact, FAA does not require the filtration of recirculated air on 
aircraft. However, when manufacturers voluntarily equip their aircraft 
models that recirculate cabin air with HEPA or other filters when they 
are certified for flight by FAA, as most do, the aircraft are required 
to continue operating with the filters. The schedule for changing the 
filters is also included in the FAA certification process. Airlines 
typically change HEPA filters after 4,000 to 12,000 hours of service to 
maintain good airflow and in accordance with manufacturers' 
recommendations.

Little information has previously been available on the extent of HEPA 
filter usage in commercial aircraft ventilation systems, though the 
Council report and many in the health community have pointed to the 
importance of HEPA filters in preventing the spread of bacteria, 
viruses, and other contaminants in aircraft cabins. As noted earlier in 
this report, the 2001 Council report recommended that FAA investigate 
and publicly report on the need for installing equipment to clean the 
air supplied to aircraft cabin ventilation systems. In the report, the 
committee did not determine how many larger aircraft were equipped with 
HEPA filters, and regional jets were not within the scope of its study. 
However, the report concluded that HEPA filters are highly effective in 
removing all airborne pathogens and other particulate matter that pass 
through them. The report further stated that the use of recirculated 
air in aircraft cabins when combined with effective HEPA filtration 
does not contribute to the spread of infectious agents. Members of the 
research community, including those from NIOSH, as well as the 
Association of Flight Attendants, have noted that given the proven 
effectiveness of HEPA filters in capturing contaminants such as 
infectious viruses and bacteria, FAA should require their use on all 
aircraft with recirculation systems.

To determine the extent of HEPA filter usage in the United Stares, we 
surveyed the largest 14 airlines[Footnote 36] in the United States that 
had Airbus, Boeing, or McDonnell Douglas aircraft that recirculate 
cabin air, and we received responses from 12 airlines. Of the 3,038 
aircraft for which we were able to obtain survey results, 15 percent 
(454 aircraft)[Footnote 37] did not use HEPA filters. All of the 
aircraft that did not use HEPA filters were older out-of-production 
models that used less effective filters. One airline has plans to 
retrofit a small number of these aircraft with HEPA filters.

We were also able to obtain some information on HEPA filter usage in 
the U.S. regional aircraft fleet by contacting the manufacturers of 
these aircraft. We found that 69 percent of these regional aircraft 
recycle cabin air (1,087 of 1,584), and only a handful of these 
aircraft are equipped with HEPA filters. The manufacturer of a new 
regional jet model[Footnote 38] offers HEPA filters as an option. 
Information we obtained from two airlines that had 29 of these aircraft 
indicated that about half (14 of 29) were equipped with HEPA filters.

We also found that 90 percent of the regional aircraft (973 of 1,087 
aircraft) that recycled cabin air would require modifications to be 
retrofitted with HEPA filters. Most of these aircraft (73 percent) had 
no provision for installing filters in their air ducts.

Consideration has also been given to filtering outside air entering an 
aircraft's ventilation system. Outside air at cruise altitudes is 
mainly free of pollutants, except for ozone. However, in the event of 
an engine or hydraulic system malfunction, outside air can become 
contaminated before it enters the ventilation system. In addition, when 
an aircraft is at the gate or taxiing, the available outside air 
contains pollutants normally present around the airport, including 
exhaust from other aircraft on the runway. For these reasons, the 2001 
Council report recommended that FAA investigate the need for and 
feasibility of installing air-cleaning equipment for removing particles 
and vapors from the air supplied to the ventilation system. As 
previously noted, FAA has put off consideration of this recommendation 
until the completion of FAA's and ASHRAE's air quality research and 
surveillance program in 2006 or 2007. One manufacturer did begin 
installing outside air filtering equipment on one of its models in 
1992. British Aerospace began equipping its BAe 146 aircraft (now out 
of production) with outside air filters as part of an effort to reduce 
cabin odors. Other manufacturers, including Boeing and Airbus, contend 
that outside air filtration is not necessary unless U.S. and European 
research indicates a problem with the quality of air entering aircraft 
ventilation systems.

Technology is Available to Remove Ozone from the Air Brought in from 
Outside the Aircraft:

Technologies are currently available for removing ozone from outside 
air. Ozone is present in the air at high altitudes on some routes, 
particularly those over the polar regions, and FAA requires that the 
airlines that fly these routes take measures to maintain cabin ozone 
levels at or below prescribed limits (e.g., using devices that convert 
ozone to oxygen). According to ATA officials, nearly all commercial 
aircraft that fly on these routes are so equipped. However, the Council 
report said that although FAA requires that ozone concentrations in 
aircraft cabins be maintained within specified limits, surveillance 
programs with accurate and reliable equipment are needed to ensure 
compliance and that the ozone converter equipment works properly. One 
study attributed elevated ozone levels that exceeded FAA limits to 
temporary ozone plumes that can appear unexpectedly. In November 2000, 
the British House of Lords, in a study of health issues in aircraft 
cabins,[Footnote 39] made a recommendation that airlines fit their 
aircraft that fly on routes where these plumes occur with ozone 
converters to minimize potential health problems. The Council report 
also identified the need for FAA to take effective measures to ensure 
that ozone does not exceed levels specified in FAA regulations, 
regardless of altitude. As noted earlier, FAA plans to monitor ozone 
levels in selected aircraft as part of its surveillance and research 
program. However, some committee members told us that the effort will 
be too limited to enable FAA to determine if ozone is present on 
aircraft not fitted with converters or whether ozone converters are 
working properly.

Increasing Ventilation Rates in Aircraft Cabins Poses Challenges:

Increasing ventilation rates on aircraft to levels approximating those 
currently required in buildings would pose technological challenges, 
and aircraft manufacturers believe such increases are not necessary. 
Raising ventilation rates would reduce the effects of some airborne 
contaminants by diluting their concentration.

According to Boeing and Airbus officials, airflow rates on their 
aircraft could be slightly increased by adjusting settings on the 
ventilation systems, but such adjustments would increase fuel 
consumption and result in higher operating costs. According to Boeing 
officials, to achieve the same airflow rates recommended for buildings, 
aircraft ventilation systems, and possibly the aircraft themselves, 
would have to undergo expensive modifications. Boeing and Airbus 
believe that unless the U.S. and European research and surveillance 
initiatives prove otherwise, ventilation rates in commercial aircraft 
are sufficient to sustain passenger and cabin crew comfort and health.

Boeing and Airbus officials told us that they are always seeking to 
improve the aircraft they build, but they believe that the ventilation 
systems in the aircraft they produce provide a healthy and relatively 
comfortable environment for passengers and cabin crew. Nevertheless, 
Boeing is considering increasing the air pressure and humidity levels 
on the 7E7, its proposed long-range, high-altitude aircraft. Airbus 
will also offer an improved air ventilation system on its new large 
aircraft, the A380. Because of the competitive nature of the aircraft 
manufacturing industry, few details are available on the 7E7 and A380 
ventilation systems. Boeing and Airbus officials noted that if current 
research and surveillance efforts indicate problems with any aspects of 
the ventilation systems in their aircraft, they would work toward 
developing the necessary technologies to deal with these problems.

Conclusions:

The combined research efforts of FAA and ASHRAE on cabin air quality 
will provide a foundation of knowledge, according to some members of 
the committee that produced the 2001 Council report on cabin air 
quality. However, as currently designed and funded, these efforts may 
not answer many long-standing questions about the effect of air quality 
on cabin occupants' health and comfort. FAA is attempting to balance 
the need to conduct additional research on the healthfulness of cabin 
air quality with other research priorities, such as improving passenger 
safety. Our prior work on airliner cabin safety and health has 
underscored the importance of setting risk-based research priorities, 
in part by establishing cost and effectiveness estimates to allow 
direct comparisons among competing research priorities. In commenting 
on this prior work, FAA cautioned that if too much emphasis is placed 
on cost/benefit analyses, potentially valuable research may not be 
undertaken. We concur in that caution. However, information on the 
nature and extent of health effects from cabin air is needed in order 
to identify potential health threats so that it can be determined if 
action is warranted to improve cabin air quality and to target research 
and development accordingly. Moreover, committee members recommended 
more study of these issues, and others in the industry have concerns 
about FAA's surveillance and research program as currently conceived. 
Committee members were particularly concerned about FAA's decision to 
delay action on ensuring that air quality regulations are adequate or 
being met on all flights. In addition, the agency's current plan to 
monitor cabin air quality on only two aircraft types during part I of 
its program will not provide FAA with information that is generalizable 
to the U.S. commercial airliner fleet. Thus, key questions that the 
agency's research and surveillance program were designed to address 
will remain unanswered if part II of FAA's program is not properly 
designed and adequately funded. Such information is also needed to 
guide the development of new technologies. Given the importance of this 
research and surveillance effort, the program needs to be well 
designed, properly funded, coordinated with international cabin air 
quality research efforts such as those ongoing in Europe and Australia, 
and conducted in accordance with accepted standards for independence 
and oversight. The Council in its 2001 report recommended that Congress 
designate a federal agency to conduct or direct the cabin air quality 
research program and recent legislation assigned FAA as the lead 
federal agency for this effort. FAA has begun a surveillance and 
research program on its own.

Furthermore, FAA has not taken steps to ensure that HEPA filters, which 
are a proven technology for eliminating some contaminants such as 
viruses and bacteria from recirculated cabin air, are used as widely as 
possible on commercial aircraft. FAA does not currently require the use 
of filters on recirculated air. Nevertheless, we found that a number of 
aircraft manufacturers and airlines voluntarily install them and that 
the vast majority of larger commercial aircraft are equipped with HEPA 
filters. However, we also found that only a few smaller regional jets 
that recirculate cabin air have HEPA or any other type of filters. FAA 
has decided to delay addressing the 2001 Council report recommendation 
calling for the agency to investigate the need for air cleaning 
equipment on aircraft ventilation systems until it completes its cabin 
air quality surveillance and research program in 2006 or 2007. FAA 
needs to determine the costs and benefits of requiring HEPA filters on 
commercial aircraft that recirculate air.

Finally, although FAA has made some progress in implementing the 
Council's recommendation regarding the need to increase the 
availability of information on health issues related to air travel, 
more needs to be done. Creating links on the FAA Web site to pertinent 
information on the CDC and WHO Web sites is a good start, but 
navigating the FAA's Web site to reach these links is difficult. In 
addition to improving the user friendliness of the FAA Web site links, 
some commenting committee members suggested that FAA should consider 
other methods for disseminating information on the health risks of 
flying, such as providing brochures for physicians to use when 
discussing these issues with patients.

Recommendations for Executive Action:

To help ensure that FAA's research and surveillance efforts on airliner 
cabin air quality answer critical outstanding questions about the 
nature and extent of potential health effects of cabin air quality on 
passengers and flight attendants, GAO recommends that the Secretary of 
Transportation direct the FAA Administrator to:

* develop a detailed plan for the research and surveillance efforts, 
including key milestones and funding estimates, in accordance with 
generally accepted practices for oversight and independence;

* appoint a committee of acknowledged experts in the fields of aircraft 
ventilation and public health, including representatives of EPA and 
NIOSH, to assist in planning and overseeing the research and 
surveillance efforts recommended by the National Research Council in 
2001;

* leverage the findings of international research on airliner cabin air 
quality to inform FAA's surveillance and research efforts; and:

* report to Congress annually on the progress and findings of the 
research and surveillance efforts and funding needs.

In order to help improve the healthfulness of cabin air for commercial 
aircraft passengers and cabin crews, the FAA Administrator should 
assess the costs and benefits of requiring the use of HEPA filters on 
commercial aircraft with ventilation systems that recirculate cabin 
air. If FAA chooses to require the use of HEPA filters, it should also 
ensure that the regulation covers the maintenance requirements for 
these filters.

In addition, to increase access to information on the health risks 
related to air travel, the FAA Administrator should direct the staff 
responsible for the FAA Web site to improve the links to other Web 
sites containing this information. The Administrator should also 
consult with medical associations and health organizations, such as 
CDC, on other ways to increase the dissemination of this information.

Agency Comments:

We provided copies of a draft of this report to the Department of 
Transportation for review and comment. FAA generally agreed with the 
report's contents and its recommendations. The agency provided us with 
oral comments, primarily technical clarifications, which we have 
incorporated as appropriate.

As agreed with your office, unless you publicly announce the contents 
of this report earlier, we plan no further distribution until 30 days 
from the report date. At that time, we will send copies of this report 
to interested congressional committees, the Secretary of 
Transportation, and the Administrator, FAA. We will also make copies 
available to others upon request. In addition, the report will be 
available at no charge on the GAO Web site at [Hyperlink, http://
www.gao.gov].

Signed by:

Please call me at (202) 512-2834 if you or your staff have any 
questions concerning this report. Major contributors to this report are 
listed in appendix VI.

Sincerely yours,

Gerald L. Dillingham: 
Director, Civil Aviation Issues:

Signed by Gerald L. Dillingham: 

[End of section]

Appendixes: 

Appendix I: Objectives, Scope, and Methodology:

The Ranking Democratic Member of the Subcommittee on Aviation, House 
Committee on Transportation and Infrastructure, asked us to provide 
information on steps that the aviation community is taking to address 
concerns about cabin air quality. Specifically, our research focused on 
the following questions: (1) What is known about the major potential 
health effects of air quality in commercial airliner cabins on 
passengers and flight attendants? (2) What actions has the National 
Research Council recommended to improve cabin air quality, and what is 
the status of those actions? (3) What technologies are available today 
to improve the air quality in commercial airliner cabins, and which, if 
any, should be required?

To answer the first question, we reviewed the December 2001 National 
Research Council report on aircraft cabin air quality, which was the 
most current and comprehensive examination of the existing literature 
on this issue and made recommendations for potential approaches for 
improving cabin air quality. We also independently reviewed many of the 
studies on issues related to cabin air quality, paying particular 
attention to those issued after the publication of the 2001 Council 
report.[Footnote 40] We also gathered information from the governments 
of Australia, Canada, and the United Kingdom and airlines. We also 
interviewed officials representing the Federal Aviation Administration 
(FAA), the World Health Organization (WHO), the Centers for Disease 
Control and Prevention (CDC), the National Institute for Occupational 
Safety and Health (NIOSH), the Aerospace Medical Association (AsMA), 
the Air Transport Association (ATA), the Association of Flight 
Attendants (AFA), the International Airline Passengers Association 
(IAPA), aircraft and air filter manufacturers, as well as experts on 
cabin air quality issues, including members of the committee that 
produced the 2001 Council report on cabin air quality.

To address the second question, we interviewed Council committee 
members about their views on how FAA was addressing the recommendations 
they made in their report. Before conducting the interviews, we 
provided the committee members with information from FAA on its plans 
for addressing the Council's recommendation. We then asked them for 
their views on the approach for addressing each of the recommendations. 
We conducted interviews with 11 of the 13 committee members; we were 
unable to contact 2 members. Of the 11 members we interviewed, 8 agreed 
to provide their views on at least some of the recommendations. Three 
members declined to address any of the recommendations, saying that 
they were outside their fields of expertise and that they had not 
followed the progress of FAA's implementation of the recommendations.

To address the third question, we interviewed representatives of 
aircraft manufacturers, filter manufacturers, FAA officials, and 
experts on aircraft ventilation systems, including members of the 
committee. To determine HEPA filter usage, we first identified the 28 
airlines that account for 99.94 percent of the revenue passenger miles 
(RPM) flown by U.S. airlines as reported in Aviation Daily for May 
2003.[Footnote 41] Fourteen of these airlines had aircraft that 
recirculate cabin air. The other 14 only had smaller regional aircraft 
or larger aircraft that did not recirculate cabin air. After selecting 
the 28 airlines, we obtained information from Air Transport World 
(Airclaims 2002 data, July 2003 edition) on the number of aircraft they 
operate by model type. We then obtained information from the aircraft 
manufacturers that allowed us to categorize the 5,354 aircraft in the 
28 airlines by whether or not they recycle air (see table 3).

Table 3: Number of Large and Regional Aircraft of Top 28 Airlines That 
Do or Do Not Recycle Cabin Air:

Aircraft size: Larger aircraft; 
Cabin air recycled: 3,422; 
Cabin air not recycled: 348; 
Total: 3,770.

Aircraft size: Regional aircraft; 
Cabin air recycled: 1,087; 
Cabin air not recycled: 497; 
Total: 1,584.

Total; 
Cabin air recycled: 4,509; 
Cabin air not recycled: 845; 
Total: 5,354.

Source: GAO.

[End of table]

Larger aircraft included the commercial aircraft manufactured by 
Airbus, Boeing, and McDonnell Douglas. Regional aircraft included 
Avions de Transport Regional (ATR), British Aerospace (BAe), 
Bombardier, Dornier, Embraer, Fokker, Jetstream, and Saab models.

Our primary focus with the larger aircraft was to determine the HEPA 
filter usage for the 3,422 larger aircraft that recycled cabin air. To 
obtain this information, we surveyed the 14 airlines that had aircraft 
in this category and obtained responses from 12 (covering 3,038 of the 
3,422 aircraft in this category). Our survey form, which we 
administered by e-mail, asked the airlines to provide the following 
information: the number of active aircraft by model type as of June 30, 
2003; the number of active aircraft with HEPA filters; the number of 
active aircraft without HEPA filters; the reasons why HEPA filters are 
not used; and, if applicable, the types of filters used if other than 
HEPA filters.

Our primary focus with the regional aircraft was to determine what 
percentage of these aircraft recycled air, and, for those aircraft that 
did recycle air, what percentage would require major modifications to 
be retrofitted with a HEPA filter. We were able to make this 
determination on the basis of information provided by the 
manufacturers. Because only a small portion of the regional aircraft 
that recycle air are capable of being fitted with HEPA filters, we did 
not survey the 13 airlines that had only regional aircraft. In the 
cases where returned surveys also included information on regional 
aircraft that could use HEPA filters with little or no retrofitting, we 
found that only a small portion were doing so.

[End of section]

Appendix II: Biographical Information on the National Research Council 
Committee:

Dr. Morton Lippman: Professor of environmental medicine and director of 
the Center for Particulate Matter Health Effects Research and of the 
Human Exposure and Health Effects Research Program at New York 
University School of Medicine.

Dr. Harriet A. Burge: Associate professor of environmental microbiology 
at the Harvard School of Public Health. Dr. Burge's current area of 
research is on the role of environmental exposures in the development 
of asthma and evaluating exposure to fungi, dust mite, cockroach, and 
cat allergens in three separate epidemiology studies assessing risk 
factors for the development of asthma.

Dr. Byron Jones: Associate dean for Research and Graduate Programs and 
director of the Engineering Experiment Station at the College of 
Engineering, Kansas State University. Dr. Jones's research interests 
are in heat and mass transfer, human thermal systems simulation, and 
thermal measurements and instrumentation.

Dr. Janet M. Macher: Air pollution research specialist with the 
Division of Environmental and Occupational Disease Control of the 
California Department of Health Services. Her research has focused on 
the evaluation of methods to collect and identify airborne biological 
material and on engineering measures to control airborne infectious and 
hypersensitivity diseases.

Dr. Michael S. Morgan: Professor in the Department of Environmental 
Health, Industrial Hygiene and Safety Program of the University of 
Washington and director of the Northwest Center for Occupational Health 
and Safety. His research is focused on human response to inhalation of 
air contaminants, including the products of combustion and volatile 
solvents, and has encompassed both ambient air contaminants and 
occupational environmental health hazards.

Dr. William W. Nazaroff: Professor of environmental engineering in the 
Department of Civil and Environmental Engineering of the University of 
California, Berkeley. His main research interest is indoor air quality, 
with emphasis on pollutant-surface interactions, transport/mixing 
phenomena, aerosols, environmental tobacco smoke, source 
characterization, exposure assessment, and control techniques.

Dr. Russell B. Rayman: Executive director of the Aerospace Medical 
Association in Alexandria, Virginia, retired from the U.S. Air Force in 
1989 with the rank of colonel after a military medical career.

Dr. John D. Spengler: The Akira Yamaguchi Professor of Environmental 
Health and Human Habitation and director of the Environmental Science 
and Engineering Program at the Harvard School of Public Health. Dr. 
Spengler's research is focused on assessment of population exposures to 
environmental contaminants that occur in homes, offices, schools, and 
during transit, as well as in the outdoor environment.

Dr. Ira B. Tager: Professor of epidemiology in the Division of Public 
Health, Biology, and Epidemiology at the University of California, 
Berkeley, and is codirector and principal investigator for the Center 
for Family and Community Health. Dr. Tager's research includes the 
development of exposure assessment instruments for studies of health 
effects of chronic ambient ozone exposure in childhood and adolescence, 
the effects of ozone exposure on pulmonary function, and the effects of 
oxidant and particulate air pollution on cardio-respiratory morbidity 
and mortality and morbidity from asthma in children.

Dr. Christiaan Van Netten: Associate professor in the Department of 
Health Care and Epidemiology at the University of British Columbia and 
head of the Division of Occupational and Environmental Health. Dr. Van 
Netten's research interests include environmental toxicology and the 
use of electrodiagnostics to monitor worker exposure to agents that 
affect the peripheral nervous system.

Dr. Bernard Weiss: Professor of environmental medicine and pediatrics at 
the University of Rochester School of Medicine and Dentistry. His 
special interest and publications lie primarily in areas that involve 
chemical influences on behavior, including the neurobehavioral 
toxicology of metals such as lead, mercury, and manganese.

Dr. Charles J. Weschler: Adjunct professor in the Department of 
Environmental and Community Medicine at the University of Medicine and 
Dentistry of New Jersey, Robert Wood Johnson Medical School/Rutgers. 
His research interests, among others, include chemical interactions 
among indoor pollutants and the chemistry of the outdoor environment as 
it impacts the indoor environment.

Dr. Hanspeter Witschi: Professor of toxicology and associate director of 
the Institute for Toxicology and Environmental Health at the University 
of California, Davis. Dr. Witschi's research interests include 
experimental toxicology, biochemical pathology, and the interaction of 
drugs and toxic agents with organ function at the cellular level.

Source: National Research Council.

[End of section]

Appendix III: Transmission of Severe Acute Respiratory Syndrome (SARS) 
on Board Aircraft Is Rare and Associated with Proximity:

Aboard aircraft, cabin occupants are confined in close quarters for 
extended periods and can be exposed to infectious diseases carried by 
other occupants. Because air travel is rapid, people can complete their 
journeys before the symptoms of a disease begin. Consequently, there 
has been much concern regarding the in-flight transmission of 
contagious diseases, particularly tuberculosis and, more recently, 
severe acute respiratory syndrome (SARS). As part of our review of 
airliner cabin air quality, we tracked the status of SARS and air 
travel.

SARS is a serious respiratory illness that has affected persons in 
Asia, North America, and Europe. According to the World Health 
Organization (WHO), as of September 26, 2003, there were an estimated 
8,098 probable cases reported in 27 countries, including 29 cases in 
the United States. There have been 774 deaths worldwide, none of which 
have occurred in the United States. The Centers for Disease Control and 
Prevention (CDC) believes SARS is caused by a previously unrecognized 
coronavirus.[Footnote 42] The symptoms of SARS can include a fever, 
chills, headache, other body aches, and a dry cough.

SARS appears to be transmitted by close personal contact, which 
includes touching the eyes, nose, or mouth after touching the skin of 
infected individuals or objects that have been contaminated with 
infectious droplets released by an infected individual while coughing 
or sneezing. People with SARS pose the highest risk of transmission to 
household members and health care personnel in close contact. Most 
cases of SARS involved people who cared for or lived with someone with 
SARS or had direct contact with objects contaminated with infectious 
droplets. Information to date suggests that people are most likely to 
be infectious when they have symptoms such as fever or cough. However, 
it is not known how long before or after their symptoms begin that 
people with SARS might be able to transmit the disease to others. Most 
of the U.S. cases of SARS have occurred among travelers returning to 
the United States from other parts of the world affected by SARS, such 
as China. According to WHO, as of September 26, 2003, the latest 
probable case of SARS reported in the United States was on July 13, 
2003. However, there is no evidence that SARS is spreading in the 
United States. WHO has reported that although the global outbreak of 
SARS has been contained, considerable uncertainty surrounds the 
question of whether SARS might recur, perhaps according to a seasonal 
pattern. Several respiratory illnesses occur much less frequently when 
temperature and humidity are high and then return when the weather 
turns cooler. WHO has also requested all countries to remain vigilant 
for the recurrence of SARS and to maintain their capacity to detect and 
respond to the reemergence of SARS, should it occur. The CDC has 
conducted broadcasts over the Internet for healthcare providers on 
preparing for the return of SARS.

WHO has reported that as of May 23, 2003, there have been 29 probable 
cases of in-flight SARS transmissions on four flights worldwide. Out of 
the 29 cases, 24 were on one flight, and 4 of the 29 cases were flight 
attendants. WHO has stated that since then there have been no reported 
cases of in-flight SARS transmissions. The WHO Director of Communicable 
Diseases stated there is a very low risk of catching SARS on an 
airplane through the airplane's ventilation system. He noted that 
nearly all of the in-flight transmissions occurred between passengers 
who were sitting near each other. This official also stated that 
airport screening procedures have been effective in keeping individuals 
displaying SARS symptoms from boarding aircraft. In October 2003, WHO 
issued a report in which it did not find evidence that SARS is an 
airborne disease. This report further stated that at all outbreak sites 
the main route of transmission was direct contact, via the eyes, nose, 
and mouth, with infectious respiratory droplets.

In December 2003, the New England Journal of Medicine published the 
results of a study on the transmission of SARS on three flights that 
transported at least one person who had SARS.[Footnote 43] The study 
found that on one flight carrying four people with SARS symptoms, one 
other person at most developed the disease, and no illness was 
documented on another flight transporting a person with presymptomatic 
SARS. However, on a third flight carrying a symptomatic person, 22 
probable cases of SARS[Footnote 44] occurred among the other 119 
passengers. According to the study, for the 22 people with illness, the 
mean time from the flight to the onset of symptoms was four days, and 
there were no recognized exposures to persons with SARS before or after 
the flight. The study found that illness in passengers was related to 
the physical proximity to the person with SARS on the flight. Illness 
was reported in 8 of the 23 passengers seated in the three rows in 
front of the person with SARS, as compared to 10 of the 88 passengers 
seated elsewhere on the aircraft. The study noted however, that 90 
percent of the passengers who became ill on the flight were seated more 
than 36 inches from the person with SARS, which had been the cutoff 
used to define the spread of SARS droplets in other investigations. The 
study authors speculated that "airborne, small particle, or other 
remote transmission may be more straightforward explanations for the 
observed distribution of cases." The study concluded that SARS 
transmissions may occur on flights carrying people in the symptomatic 
stages of the disease and that measures to reduce the risk of 
transmission are warranted.

In November of 2003, more than 50 leading SARS researchers from 15 
countries concluded that a safe and effective vaccine would be an 
important complement to existing SARS control strategies. Most of the 
experts agreed, however, that a SARS vaccine will not be available in 
time, should an epidemic reoccur in the near future. A WHO official 
stated that the licensing and commercialization of a SARS vaccine could 
probably not be realized in 2004.

According to the International Air Transport Association (IATA), 
passengers are not at risk from being infected with the SARS virus from 
the cabin crew, who must be medically fit, without SARS symptoms, and 
physically capable to fly and fulfill their duties. CDC has stated that 
there is currently no evidence that a person can be infected with SARS 
from handling baggage or goods, because the primary means of infection 
is close personal contact. CDC has also stated the transmission of SARS 
has been associated with close contact with people with SARS symptoms, 
such as passengers on an aircraft.

The CDC has issued travel alerts and advisories for travel to areas 
affected by SARS. A travel advisory recommends that nonessential travel 
be deferred; in contrast, a travel alert informs travelers of the 
health concern and provides advice about specific precautions. The CDC 
recommends that if SARS is suspected in an outpatient setting, 
healthcare providers should provide and place a surgical mask over the 
person's nose and mouth. The CDC further recommends that if this is not 
feasible, the person with SARS should be asked to cover his/her mouth 
with a disposable tissue when coughing, sneezing, or talking. WHO has 
urged airport officials in countries affected with SARS outbreaks to 
take precautionary screening measures, such as asking passengers if 
they have had contact with anyone who has had the disease. U.S. 
airlines that fly to Asia report that they are following CDC and WHO 
guidelines. FAA has links to the CDC and WHO guidelines on its Web 
site. U.S. airlines that do not fly internationally are not modifying 
their procedures because they see no SARS risk to cabin occupants. 
According to ATA officials, U.S. airlines that do not fly 
internationally were not advised by CDC to modify procedures because 
there was no evidence of community transmission of SARS in the United 
States. However, all ATA-member airlines cooperated fully with CDC in 
instances where there was a possible person with SARS who might have 
transferred from an international to a domestic flight.

[End of section]

Appendix IV: European CabinAir Study: Scope and Methodology:

In 2001, Building Research Establishment, Ltd. (BRE)[Footnote 45] 
initiated a study on cabin air quality that was estimated to cost $8 
million. The following link provides the official description of the 
effort as posted on BRE's Internet site: [Hyperlink, http://
projects.bre.co.uk/envdiv/cabinair/work_programme.html]:

To further the industry's understanding of what is known about air 
quality issues by assessing the current level of air quality found in 
aircraft cabins, BRE will monitor four generic aircraft types in flight 
and assess cabin air quality and ventilation system performance, 
including the effects of passenger density and flight duration. A total 
of 50 such flights are planned. The findings will identify current best 
practice and will be used to improve understanding of (1) what 
constitutes good cabin air; (2) the impact on the safety, health, and 
comfort of passengers and cabin crew; and (3) the effects on operating 
costs, fuel energy use, and the external environment.

To identify the technology (i.e., environmental control systems 
including filtration and air distribution) that is available to improve 
cabin air quality, BRE will develop new designs to address various air 
quality issues, including the control of carbon dioxide, 
humidification, outside air supply, and the recirculation and 
filtration of air. Operating costs and energy consumption will be 
analyzed in relation to environmental impacts. New designs must be 
suitable for retrofitting to existing aircraft, either as complete 
environmental control systems or as subsystems within existing units. 
The overall intention is to make environmental control systems flexible 
and easy to operate. For example, improved systems might enable the 
crew to match the system to the passenger load factor, reduce bleed 
air, or provide additional comfort in different areas of the cabin.

BRE will seek to improve the performance of filtration systems and then 
develop new technologies and systems. It will assess existing 
filtration systems and consider how the installation process and 
activities such as maintenance, lifting, and cleaning affect 
performance. A technology demonstrator rig will be developed to test 
new filtration systems. New and enhanced features will be developed to 
mitigate such problems as the recirculation of pollutants, bacteria, 
and viruses. Other major factors include the compatibility of the 
filtration systems with the overall environmental control system, 
operational costs, and energy consumption.

The effectiveness of current air distribution systems will be gauged 
through in-flight monitoring. New design strategies and technologies, 
such as personal controls, will be developed with the goal of 
maximizing the effectiveness of cabin ventilation. The study will also 
look at ways of making the distribution system more easily integrated 
with aircraft design.

To assess and determine potential improvements to existing standards 
and performance specifications for the cabin environment, BRE will 
assess existing standards. Potential improvements to existing standards 
and specifications will be determined. Checks will be carried out to 
ensure the feasibility of the performance specifications and costs and 
to identify any environmental implications. New performance indexes and 
comfort criteria will also be defined, and BRE will develop a model to 
be tested.

[End of section]

Appendix V: Surveillance and Research Programs:

Key recommendations of the Council report were to establish 
surveillance and research programs to determine effects of cabin air 
quality on aircraft occupants' health and comfort.

Surveillance Program:

The following is a detailed description of these programs as stated in 
the Council report.

Surveillance program objectives:

* To determine aircraft compliance with existing Federal Aviation 
Regulations (FARS) for air quality.

* To characterize accurately air quality and establish temporal trends 
of air-quality characteristics in a broad sample of representative 
aircraft.

* To estimate the frequency of nonroutine operations in which serious 
degradation of cabin air quality occurs.

* To systematically document health effects or complaints of passengers 
and crew related to routine conditions of flight or air-quality 
incidents; to be effective, this effort must be conducted and 
coordinated in conjunction with air-quality monitoring.

Surveillance program approach:

* Continuously monitor and record ozone, carbon monoxide, and carbon 
dioxide, fine particles, cabin pressure, temperature, and relative 
humidity.

* Sample a representative number of flights over a period of 1 to 2 
years.

* Continue to monitor flights to ensure accurate characterization of 
air quality as new aircraft come online and aircraft equipment ages or 
is upgraded.

* Conduct a program for the systematic collection, analysis, and 
reporting of health data with the cabin crew as the primary study 
group.[Footnote 46]

Research Program:

The following is a detailed description of the research program, 
including long-standing questions regarding air quality, objectives, 
and program approach.

Outstanding air quality-related questions to be addressed by the 
research program:

* How is the ozone concentration in the cabin environment affected by 
various factors (e.g., ambient concentrations, reaction with surfaces, 
the presence and effectiveness of catalytic converters) and what is the 
relationship between cabin ozone concentrations and health effects on 
cabin occupants?

* What is the effect of cabin pressure altitude on susceptible cabin 
occupants, including infants, pregnant women, and people with 
cardiovascular disease?

* Does the environmental control system (ECS) provide sufficient 
quantity and distribution of outside air to meet the FAA regulatory 
requirements, and to what extent is cabin ventilation associated with 
complaints from passengers and cabin crew? Can it be verified that 
infectious disease agents are transmitted primarily between people who 
are in close contact? Does recirculating cabin air increase cabin 
occupants' risk of exposure?

* What is the toxicity of the constituents or degradation products of 
engine lubricating oils, hydraulic fluids, and de-icing fluids, and is 
there a relationship between exposures to them and reported health 
effects on cabin crew? How are these oils, fluids, and degradation 
products distributed from the engines into the ECS and throughout the 
cabin environment?

* What are the magnitudes of exposures to pesticides in aircraft 
cabins, and what is the relationship between the exposures and reported 
symptoms?

* What is the contribution of low relative humidity to the perception 
of dryness, and do other factors cause or contribute to the irritation 
associated with the dry cabin environment during flight?

Research program objectives:

* To investigate possible association between specific air quality 
characteristics and health effects or complaints.

* To evaluate the physical and chemical factors affecting specific air 
quality characteristics in aircraft cabins.

* To determine whether FARS for air quality are adequate to protect 
health and ensure the comfort of passengers and crew.

* To determine exposure to selected contaminants (e.g., constituents of 
engine oils and hydraulic fluids, their degradation products, and 
pesticides) and establish their potential toxicity more fully.

Research program approach:

* Use continuous monitoring data from surveillance program when 
possible.

* Monitor additional air quality characteristics on selected flights as 
necessary (e.g., integrated particulate-matter sampling to assess 
exposure to selected contaminants).

* Identify and monitor "problem" aircraft and review maintenance and 
repair records to evaluate issues associated with air quality 
incidents.

* Collect selected health data (e.g., pulse-oximetry data to assess 
arterial oxygen saturation of passengers and crew).

* Conduct laboratory and other ground-based studies to characterize air 
distribution and circulation and contaminant generation, transport, and 
degradation in the cabin and the ECS.

[End of section]

Appendix VI: GAO Contacts and Staff Acknowledgments:

GAO Contacts:

Gerald L. Dillingham, (202) 512-2834 Beverly L. Norwood, (202) 512-
2834:

Staff Acknowledgments:

In addition to the individuals named above, Kevin Bailey, Jim Geibel, 
David Ireland, Bert Japikse, Stanley Kostyla, Edward Laughlin, Donna 
Leiss, and Maria Romero made key contributions to this report.

[End of section]

Selected Bibliography:

[End of section]

American Society of Heating, Refrigerating and Air-Conditioning 
Engineers. Standard 62-2001, Ventilation for Acceptable Indoor Air 
Quality. Atlanta, GA: 2001.

Barnas, Gary P. Altitude Sickness: Preventing Acute Mountain Sickness. 
Milwaukee, WI: Medical College of Wisconsin, June 4, 1997. [Hyperlink, 
http://healthlink.mcw.edu/article/907195877.html] (accessed June 19, 2003).

California Department of Health Services, Occupational Illness Among 
Flight Attendants Due to Aircraft Disinsection, California Department 
of Health Services, [Hyperlink, http://www.dhs.ca.gov/ohb/OHSEP/
disinsection.pdf] (accessed Nov. 10, 2003).

Centers for Disease Control. Updated Interim Domestic Infection Control 
Guidance in the Health-Care and Community Setting for Patients with 
Suspected SARS, Centers for Disease Control, [Hyperlink, http://
www.cdc.gov/ncidod/sars/infectioncontrol.htm] (accessed May 13, 2003).

Environmental Protection Agency. Air Pollution Technology Fact Sheet on 
High Efficiency Particulate and Ultra low Penetration Air Filters. 
Research Triangle Park, NC: July 15, 2003.

Environmental Protection Agency. Indoor Air Facts Number 4 (revised): 
Sick Building Syndrome. Washington, D.C.: February 10, 2003.

Federal Aviation Administration. Report to the Administrator on the 
National Research Council Report "The Airliner Cabin Environment and 
the Health of Passengers and Crew." Washington, D.C.: February 6, 2002.

Gratz, Norman G., Robert Steffen, William Cocksedge. "Why Aircraft 
Disinsection?" Bulletin of the World Health Organization 78 (8) (2000): 
995-1004.

Hocking, Martin B. "Indoor Air Quality: Recommendations Relevant to 
Aircraft Passenger Cabins." American Industrial Hygiene Association 
Journal 59 (1998): 446-454.

Hocking, Martin B. "Trends in Cabin Air Quality on Commercial Aircraft: 
Industry and Passenger Perspectives." Reviews on Environmental Health 
17, 1 (2002): 1-49.

Maresh, Carl M., Lawrence E. Armstrong, Stravos A. Kavouras, George J. 
Allen, Douglas J. Casa, Michael Whittlesey, and Kent E. LaGrasse. 
"Physiological and Psychological Effects Associated with High Carbon 
Dioxide Levels in Healthy Men." Aviation, Space, and Environmental 
Medicine 68, 1 (1997): 41-45.

MedicineNet.com. Definitions of Bacteria, Virus, and Coronavirus, 
MedicineNet.com, 
[Hyperlink, http://www.medterms.com/script/main/art.asp?ArticleKey=13954] 
[Hyperlink, http://www.medicinenet.com/script/main/art.asp?li=MNI&ArticleKey=5997&pf=3] (accessed May 12, 2003) and 
[Hyperlink, http://www.medterms.com/script/main/art.asp?ArticleKey=22789] (accessed October 14, 2003).

Military Specification. MIL-E-5007D, General Specifications for 
Aircraft Turbojet and Turbofan Engines. 1973.

Nagda, Niren L., Harry E. Rector, Zhidong Li, David R. Space. "Aircraft 
Cabin Air Quality: A Critical Review of Past Monitoring Studies," Air 
Quality and Comfort in Airliner Cabins, ASTM STP 1393, N. L. Nagda, 
Ed., American Society for Testing and Materials (2000): 215-239.

National Research Council. The Airliner Cabin Environment: Air Quality 
and Safety. National Academy Press. Washington, D.C.: 1986.

National Research Council. The Airliner Cabin Environment and the 
Health of Passengers and Crew. National Academy Press. Washington, 
D.C.: Distributed electronically December 2001; bound report 
copyrighted 2002.

Olsen, Sonja J. et al. "Trasmission of Severe Acute Respiratory 
Syndrome on Aircraft." The New England Journal of Medicine 349; 25 
(2003): 2416-2422.

Parliament of the Commonwealth of Australia. Rural and Regional Affairs 
and Transport References Committee. Australian Senate Air Safety and 
Cabin Quality in the BAe 146 Aircraft. Canberra: 2000.

Rayman, Russell B. "Cabin Air Quality." Aviation, Space and 
Environmental Medicine 73 (2002): 211-215.

Society of Automotive Engineers. ARP 4418, Procedure for Sampling and 
Measurement of Engine Generated Contaminants in Bleed Air Supplies from 
Aircraft Engines Under Normal Operating Conditions. Warrendale, PA: 
1995.

Society of Automotive Engineers. ARP 1270, Aircraft Cabin 
Pressurization Control Criteria. Warrendale, PA: 2000.

The House of Lords, Select Committee on Science and Technology. Air 
Travel and Health,5TH Report HL Paper 121-I. Session 1999-2000. London: 
2000.

U.S. Department of Transportation, Office of the Inspector General. 
Further Delays in Implementing Occupational Safety and Health Standards 
for Flight Attendants Are Likely. AV-2001-102. Washington, D.C.: 
September 26, 2001.

U.S. General Accounting Office. SARS Outbreak: Improvements to Public 
Health Capacity Are Needed for Responding to Bioterrorism and Emerging 
Infectious Diseases. [Hyperlink, http://www.gao.gov/cgi-bin/
getrpt?GAO-03-769T]. Washington, D.C.: May 7, 2003.

U.S. General Accounting Office. Serve Acute Respiratory Syndrome: 
Established Infectious Disease Control Measures Helped Contain Spread, 
But a Large Scale Resurgence May Pose Challenges. [Hyperlink, http://
www.gao.gov/cgi-bin/getrpt?GAO-03-1058T]. Washington, 
D.C.: July 30, 2003.

U.S. General Accounting Office. Aviation Safety: Advancements Being 
Pursued to Improve Airliner Cabin Safety and Health. [Hyperlink, http:/
/www.gao.gov/cgi-bin/getrpt?GAO-04-33] GAO-04-33. Washington, D.C.: 
October 3, 2003.

World Health Organization. International Travel and Health, World 
Health Organization, [Hyperlink, http://www.who.int/ith/
chapter02_01.html] http://www.who.int/ith/chapter02_01.html (accessed 
July 24, 2003).

World Health Organization. Tuberculosis and Air Travel: Guidelines for 
Prevention and Control World Health Organization, [Hyperlink, http://
www.who.int/gtb/publications/aircraft/] (accessed Oct. 1, 2003).

Zitter, Jessica, Peter Mazonson, Dave Miller, Stephen Hulley, and John 
Balmes. "Aircraft Cabin Air Recirculation and Symptoms of the Common 
Cold." Journal of the American Medical Association 288 (2002): 483-486.

(540060):

FOOTNOTES

[1] Although airliners are pressurized, the air pressure in an aircraft 
cabin is lower than it is at sea level. Airliners are required to be 
pressurized to an altitude that is not higher than 8,000 feet. This is 
about three-fourths the air pressure at sea level.

[2] According to the World Health Organization (WHO), there is a very 
low risk of catching SARS through an airplane's ventilation system. 
SARS is believed to be transmitted based on proximity to an infected 
individual. However, WHO reported that as of May 23, 2003, there were 
29 probable cases of in-flight SARS transmissions on four flights. See 
appendix III for more information on SARS.

[3] The National Research Council is the principal operating arm of the 
National Academy of Sciences and the National Academy of Engineering. 

[4] National Research Council. The Airliner Cabin Environment and the 
Health of Passengers and Crew, National Academy Press (Washington, 
D.C.: Distributed electronically December 2001; bound report 
copyrighted 2002).

[5] See the Selected Bibliography at the end of this report and, in 
particular, Hocking, Martin B., "Trends in Cabin Air Quality on 
Commercial Aircraft: Industry and Passenger Perspectives," Reviews on 
Environmental Health 17, 1 (2002): 1-49; and Rayman, Russell B., "Cabin 
Air Quality," Aviation, Space and Environmental Medicine 73 (2002): 
211-215. 

[6] The NRC committee consisted of 13 members. We attempted to contact 
all 13 members. We interviewed 11, and 8 members responded to cabin air 
quality questions and the implementation status of their 
recommendations. Of the 11 committee members interviewed, 3 declined to 
address our questions, stating that they did not follow the progress of 
FAA's implementation of the recommendations. For example, 1 member 
stated that as a toxicologist, he could not comment on the overall 
approach FAA is taking to address the NRC recommendations.

[7] For purposes of this report, we use the Environmental Protection 
Agency's definition of HEPA, which is a filtering efficiency of 99.97 
percent. 

[8] Of the 11 members interviewed, 8 agreed to address our questions 
concerning the committee recommendations (see app. I). 

[9] National Research Council, The Airliner Cabin Environment: Air 
Quality and Safety, National Academy Press (Washington, D.C.: 1986) and 
National Research Council, The Airliner Cabin Environment and the 
Health of Passengers and Crew, National Academy Press (Washington, 
D.C.: Distributed electronically December 2001; bound report 
copyrighted 2002).

[10] The 2001 Council study reported that the effects of ozone vary 
with latitude, altitude, and season and that the concentration of ozone 
is much higher at cruise altitudes in high latitudes (greater than 
approximately 60°N) than at low latitudes (approximately 30°N), 
resulting in higher concentrations of ozone on polar flights.

[11] FAA does not require these filters; however, our survey of U.S. 
airlines found that 85 percent of the large aircraft (those that carry 
100 passengers or more) currently use HEPA filters. 

[12] The American Society of Heating, Refrigerating and Air-
Conditioning Engineers (ASHRAE) advances the arts and sciences of 
heating, ventilation, air conditioning, refrigeration, and related 
human factors to serve the evolving needs of the public.

[13] According to FAA officials, FAA regulations have always required 
limitations on certain contaminants (e.g., carbon monoxide and carbon 
dioxide). Later amendments added ozone and changed the ventilation 
requirements. However, these officials stressed that airplanes are 
certified to the regulations in effect at a certain time prior to their 
manufacture. Only the latest certified airplanes will have had to meet 
the latest amendment level for the regulations governing the cabin 
environment, such as a 1996 amendment which added the requirement that 
each occupant be provided with 0.55 pounds (equivalent to 10 cubic 
feet) of fresh air per minute under standard operating conditions. 

[14] ATA officials noted that these symptoms are also consistent with a 
host of other causes, such as lack of sleep (perhaps due to difficulty 
in adjusting to different time zones), dehydration (possibly from 
drinking too much caffeine or alcohol and not enough water during a 
long flight), the effect of changes in climate, or exposure to 
contaminants in other settings. 

[15] The Wendell H. Ford Aviation Investment and Reform Act for the 
21st Century (AIR-21), Public Law 106-181, April 5, 2000.

[16] The environmental control system includes devices that pressurize 
the cabin in flight, control thermal conditions in the cabin, and 
ventilate the cabin with outside air to prevent a buildup of 
contaminants that might cause discomfort or present a health hazard.

[17] The ventilation rate is the flow of outside air supplied to the 
cabin for ventilation and it does not normally include recirculated air 
even though recirculated air may be used for cabin ventilation.

[18] According to FAA officials, a comparison of ventilation rates for 
buildings and aircraft is not valid and that "sick building syndrome" 
should not be applied to aircraft. Furthermore, both FAA and Boeing 
officials told us that the new ASHRAE standards for buildings create 
two sets of building standards for ventilation--one for high density 
buildings and another for low density buildings. Boeing officials said 
that under this standard, high density buildings would have lower 
airflow rates per occupant, and that high density buildings are most 
comparable to airplanes with high density occupancy.

[19] Disinsection is the process of spraying the aircraft cabin with 
insecticide to prevent the conduction of insects such as mosquitoes 
from one country to another. The spraying is often done while 
passengers and crewmembers are still on board. The United States 
terminated this practice in 1979 because of health concerns and doubts 
about the effectiveness of the spraying. Over the years, a number of 
countries have changed their policies regarding the spraying of 
pesticides. The Department of Transportation is studying alternative 
technological methodologies, including air curtains to prevent airborne 
insects from flying into the aircraft cabin.

[20] World Health Organization, Tuberculosis and Air Travel: Guidelines 
for Prevention and Control (Geneva, Switzerland: Aug. 27, 2003).

[21] Zitter, Jessica, Peter Mazonson, Dave Miller, Stephen Hulley, and 
John Balmes, "Aircraft Cabin Air Recirculation and Symptoms of the 
Common Cold," Journal of the American Medical Association 288 (2002): 
483-486.

[22] Olsen, Sonja J. et al., "Transmission of the Severe Acute 
Respiratory Syndrome on Aircraft," The New England Journal of Medicine 
349; 25 (2003): 2416-2422.

[23] U.S. General Accounting Office, Aviation Safety: Advancements 
Being Pursued to Improve Airliner Cabin Safety and Health, GAO-04-33 
(Washington, D.C.: October 3, 2003).

[24] Vision 100--Century of Aviation Reauthorization Act,'' passed by 
Congress in November 2003, requires that FAA, at a minimum: 1) conduct 
surveillance to monitor ozone in the cabin on a representative number 
of flights and aircraft to determine compliance with existing 
regulations for ozone, 2) collect pesticide exposure data to determine 
exposures of passengers and crew, 3) analyze samples of residue from 
aircraft ventilation ducts and filters after air quality incidents to 
identify potential exposure of contaminants to passengers and crew, 4) 
analyze cabin air pressure and altitude, and 5) establish an air 
quality incident reporting system. The FAA administrator is to report 
the findings to Congress no later than 30 months after the date of the 
act's enactment.

[25] NIOSH conducted the study over 2 years on 33 commercial flights on 
10 different types of airplanes owned by four air carriers. NIOSH 
initially surveyed female flight attendants on reproductive health, but 
the survey was later expanded to include respiratory effects. The study 
did not include direct linkage to measurement of cabin environment 
conditions. The survey respondents flew on a wide variety of aircraft 
in which the cabin environment was not sampled.

[26] Circadian rhythm is the body's internal resting or wakefulness 
schedule over the course of a day. Outside influences, such as jet lag, 
can disrupt the circadian rhythm temporarily.

[27] FAA's fiscal year 2004 facilities and equipment budget includes 
$8.5 million to develop and demonstrate a chemical/biological detection 
and mitigation capability and decontamination procedures for aircraft 
occupants and for returning the aircraft to service. 

[28] The minimum number of flights to be included will depend on the 
recommendations of part I and on the availability of research funds and 
will be specified in the solicitation for part II to be released by 
ASHRAE in the future.

[29] The European cabin air study is known as CabinAir. 

[30] Building Research Establishment, Ltd. (BRE) is a high-level 
research-based consultancy organization, owned by a not-for-profit 
entity headquartered in the United Kingdom. BRE provides the aviation 
industry with expert advice on cabin environment issues and, 
particularly, on air quality in passenger aircraft.

[31] In addition to Europe's cabin air study (CabinAir), Australia has 
addressed cabin air quality issues through the creation of a Reference 
Group on Cabin Air Quality. The Reference Group is responsible for 
following the progress of and analyzing the outcomes of international 
research and development. The Reference Group comprises government 
agencies, industry representatives, employee/union representatives, 
and representatives of aircraft and engine manufacturers.

[32] The flight attendant groups have actively lobbied for independent 
research that is not funded and controlled by companies that have a 
financial interest in the outcome. 

[33] ASHRAE writes standards and guidelines in its fields of expertise 
to guide industry in the delivery of goods and services to the public. 
Currently, it has some 87 active standards and guideline project 
committees, addressing such broad areas as indoor air quality, thermal 
comfort, energy conservation in buildings, reduction of refrigerant 
emissions, and the designation and safety classification of 
refrigerants.

[34] The Environmental Protection Agency states that HEPA filters are 
to be 99.97 percent efficient for the removal of Particulate Matter 
(PM) that is greater than or equal to 0.3 micrometer (mm) in diameter.

[35] Installing HEPA filters on the A300 would require some 
modification. 

[36] We used revenue passenger miles (RPM) as reported in Aviation 
Daily for May 2003 to identify the largest U.S. carriers. This list 
identified the largest 28 airlines, 14 of which had the larger aircraft 
that recirculate cabin air. The other 14 airlines only had smaller 
regional aircraft or larger aircraft that did not recycle cabin air. An 
RPM is a standard unit of passenger demand for air transport, defined 
as one fare-paying passenger transported one mile. We obtained the 
model information for these carriers from data published in Air 
Transport World (July 2003).

[37] We obtained information on 3,038 larger aircraft that recycled 
cabin air, 454 of which did not have a HEPA filter. We were not able to 
obtain survey results for another 384 aircraft. Of these 384, 56 (15 
percent) of the aircraft were older models that most airlines had not 
retrofitted with HEPA filters. Our study included 3,770 larger 
aircraft, of which 348 did not recycle cabin air.

[38] HEPA filters are available for the CRJ700 manufactured by 
Bombardier.

[39] The House of Lords, Select Committee on Science and Technology, 
Air Travel and Health, 5th Report HL.

[40] See the Selected Bibliography at the end of this report and, in 
particular, Hocking, Martin B., "Trends in Cabin Air Quality on 
Commercial Aircraft: Industry and Passenger Perspectives," Reviews on 
Environmental Health 17, 1 (2002): 1-49; and Rayman, Russell B., "Cabin 
Air Quality," Aviation, Space and Environmental Medicine 73 (2002): 
211-215. 

[41] A revenue passenger mile is a standard unit of passenger demand 
for air transport, defined as one fare-paying passenger transported one 
mile.

[42] A coronavirus is so named because it looks like a corona or halo 
when viewed under an electron microscope. Two human coronaviruses cause 
about 30 percent of common colds. Coronavirses have been found to 
infect cattle, pigs, horses, turkeys, chickens, cats, dogs, rats, and 
mice. 

[43] Olsen, Sonja J. et al., "Transmission of the Severe Acute 
Respiratory Syndrome on Aircraft," The New England Journal of Medicine 
349; 25 (2003): 2416-2422.

[44] According to the study, laboratory confirmed SARS developed in 16 
persons, 2 others were given diagnosis of probable SARS and four were 
reported to have SARS but could not be interviewed by the study team. 
WHO reported that as of May 23, 2003, 24 probable SARS transmissions 
occurred on this flight. The study does not indicate the reason for the 
discrepancy.

[45] Building Research Establishment, Ltd. (BRE) is a high-level 
research-based consultancy organization, owned by a not-for-profit 
entity headquartered in the United Kingdom. BRE provides the aviation 
industry with expert advice on cabin environment issues and 
particularly on air quality in passenger aircraft.

[46] On March 4, 2003, FAA announced the creation of a voluntary 
program for air carriers, called the Aviation Safety and Health 
Partnership Program. Through this program, the agency intends to enter 
into partnership agreements with participating air carriers, which 
will, at a minimum, make data on their employees' injuries and 
illnesses available to FAA for collection and analysis. 

GAO's Mission:

The General Accounting Office, the investigative arm of Congress, 
exists to support Congress in meeting its constitutional 
responsibilities and to help improve the performance and accountability 
of the federal government for the American people. GAO examines the use 
of public funds; evaluates federal programs and policies; and provides 
analyses, recommendations, and other assistance to help Congress make 
informed oversight, policy, and funding decisions. GAO's commitment to 
good government is reflected in its core values of accountability, 
integrity, and reliability.

Obtaining Copies of GAO Reports and Testimony:

The fastest and easiest way to obtain copies of GAO documents at no 
cost is through the Internet. GAO's Web site ( www.gao.gov ) contains 
abstracts and full-text files of current reports and testimony and an 
expanding archive of older products. The Web site features a search 
engine to help you locate documents using key words and phrases. You 
can print these documents in their entirety, including charts and other 
graphics.

Each day, GAO issues a list of newly released reports, testimony, and 
correspondence. GAO posts this list, known as "Today's Reports," on its 
Web site daily. The list contains links to the full-text document 
files. To have GAO e-mail this list to you every afternoon, go to 
www.gao.gov and select "Subscribe to e-mail alerts" under the "Order 
GAO Products" heading.

Order by Mail or Phone:

The first copy of each printed report is free. Additional copies are $2 
each. A check or money order should be made out to the Superintendent 
of Documents. GAO also accepts VISA and Mastercard. Orders for 100 or 
more copies mailed to a single address are discounted 25 percent. 
Orders should be sent to:

U.S. General Accounting Office

441 G Street NW,

Room LM Washington,

D.C. 20548:

To order by Phone: 

 Voice: (202) 512-6000:

 TDD: (202) 512-2537:

 Fax: (202) 512-6061:

To Report Fraud, Waste, and Abuse in Federal Programs:

Contact:

Web site: www.gao.gov/fraudnet/fraudnet.htm E-mail: fraudnet@gao.gov

Automated answering system: (800) 424-5454 or (202) 512-7470:

Public Affairs:

Jeff Nelligan, managing director, NelliganJ@gao.gov (202) 512-4800 U.S.

General Accounting Office, 441 G Street NW, Room 7149 Washington, D.C.

20548: