Aviation Safety: More Research Needed on the Effects of Air Quality on Airliner Cabin Occupants
Published: 2004-01-16T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: 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.
section_title: What GAO Found
paragraphs: 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.

section_title: Letter
paragraphs: 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 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.  In 2001, the National  Research Council 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.
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. 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 membersof 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 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.
subsections: section_title: Background
paragraphs: 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.  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.
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 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.  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).  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.
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.  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.
section_title: Despite a Number of Studies, Data Are Lacking About the Effects of Air Quality On Cabin Occupants
paragraphs: 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.   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, 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 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 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. 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, 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.
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.  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 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.)
section_title: FAA has Taken Action to Address Council Recommendations On Cabin Air Quality, but These Efforts Could Be Improved
paragraphs: 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.
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. 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.
subsections: section_title: Council Recommendations Calling for Cabin Air Quality Surveillance and Research Programs
paragraphs: 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.
subsections: section_title: Council Concluded That Surveillance and Research Programs Needed to Answer Outstanding Questions Concerning Cabin Air Quality
paragraphs: 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.
section_title: FAA Has Taken the Lead in Developing Surveillance and Research Programs
paragraphs: 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.  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. 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, 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.  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. 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.
section_title: Committee Members Concerned about Scope, Independence, and Funding of FAA Surveillance and Research Program
paragraphs: 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 is currently coordinated by Building Research  Establishment, Ltd. (BRE). 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.
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, 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.
section_title: Council’s Recommendations Concerning FAA Oversight of Aircraft Ventilation Systems
paragraphs: 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 (CO), ozone (O), 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) 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.
section_title: Council Recommendation Concerning Airborne Allergens
paragraphs: 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.
section_title: Council Recommendation Concerning Health Information
paragraphs: 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).
section_title: Council Recommendation Concerning Aircraft Ventilation System Shutdown
paragraphs: 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.
section_title: Some Technologies Exist for Improving Cabin Air Quality, but There Are Questions About Whether They Should be Required
paragraphs: 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.
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.
subsections: section_title: High Efficiency Particulate Filters Are an Effective Technology for Cleaning Recirculated Air
paragraphs: 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.  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.  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 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) 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 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.
section_title: Technology is Available to Remove Ozone from the Air Brought in from Outside the Aircraft
paragraphs: 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, 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.
section_title: Increasing Ventilation Rates in Aircraft Cabins Poses Challenges
paragraphs: 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.
section_title: Conclusions
paragraphs: 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.
section_title: Recommendations for Executive Action
paragraphs: 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.
section_title: Agency Comments
paragraphs: 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 http://www.gao.gov.
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.
section_title: Objectives, Scope, and Methodology
paragraphs: 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. 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.
A revenue passenger mile is a standard unit of passenger demand for air transport, defined  as one fare-paying passenger transported one mile.
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.
section_title: Biographical Information on the National Research Council Committee
paragraphs: 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
section_title: Transmission of Severe Acute Respiratory Syndrome (SARS) on Board Aircraft Is Rare and Associated with Proximity
paragraphs: 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.  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.
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.
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.
section_title: European CabinAir Study: Scope and Methodology
paragraphs: In 2001, Building Research Establishment, Ltd. (BRE) 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: 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.
section_title: Surveillance and Research Programs
paragraphs: 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.
subsections: section_title: Research Program
paragraphs: The following is a detailed description of the research program, including  long-standing questions regarding air quality, objectives, and program  approach.
subsections: section_title: Outstanding air quality- related questions to be addressed by the research program
paragraphs: 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?
section_title: Research program objectives
paragraphs: 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.
section_title: GAO Contacts and Staff Acknowledgments
subsections: section_title: GAO Contacts
section_title: Staff Acknowledgments
paragraphs: 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.
section_title: Selected Bibliography
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