Air quality questionable for take-off
03/01/2001
FAA, ASHRAE studies underway to determine if airplane air causes illness
Sheila Galatowitsch
WASHINGTON, DC—IF YOU'VE gotten sick after traveling by air recently, it probably won't make you feel better to know that there is no direct evidence linking air contamination in airplanes with health-related problems.
In fact, the Federal Aviation Administration (FAA) contends that the air in airplanes is cleaner than in the average office building. Various monitoring studies over the years have confirmed this view.
 Jones: Standards body is regrouping. |
But complaints from the traveling public and a mounting stack of medical records from flight attendants indicate more research is necessary. Several studies are underway to determine if the air you breathe on cross-country flights has the potential to make you sick. Even the most ardent advocate of higher air quality standards in aircraft—the Association of Flight Attendants (AFA)—sees cause for optimism in recent developments.
According to the AFA's Judith Murawski, an industrial hygienist in the labor group's Department of Air Safety and Health, there are three main problems with air quality in airplanes. The first is the 8,000 feet altitude level maintained inside the aircraft cabin itself, a level established in a 1957 FAA regulation.
The amount of oxygen in pressurized air at this altitude is significantly less than in air on the ground. Less oxygen in the air could lead to dizziness, headaches and nausea for flyers with health or weight concerns. The AFA is pushing the FAA to review the 8,000 feet requirement, which was originally based on blood oxygen data collected from "superfit" pilots and military men, says Murawski, not from flight attendants or passengers.
A second problem centers on ventilation rates. There is no fresh air ventilation standard for aircraft flying today, most of which recirculate cabin air to save on fuel costs, a practice begun in the 1980s. In 1996, the FAA did establish a minimum fresh air ventilation rate of 10 cubic feet per minute per person (cfm/p), but that requirement applies only to new aircraft designs that are not yet in the air.
"Current aircraft types don't have to meet that standard. They can operate at whatever flow rate they want to," says Murawski. Most aircraft operate with fresh air ventilation rates of 5 to 10 cfm/p. The minimum recommendation for public buildings, set by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), is 15 cfm/p.
A lack of fresh-flowing air leads to a third problem with air quality in planes: the levels of contaminants in the air. For in-flight air supply, air is siphoned or "bled" off from engine thrust. Air passing through engine compressors and rear-mounted engines on its way to the cabin could be contaminated with lubricating oils, hydraulic fluids, lavatory water and even sewage. The auxiliary power unit (APU) used for power and air supply while the plane is on the ground can also prove a source of contaminants.
Carbon monoxide and the neurotoxin tricresyl phosphate (TCP), an agent added to engine oil, are two contaminants topping the AFA's concerns. Flight attendants have reported symptoms consistent with carbon monoxide poisoning and exposure to TCP, including severe nausea, tunnel vision and memory loss. In some cases, these symptoms have been correlated to mechanical problems on a specific flight, says Murawski.
Humidity levels, the presence of ozone and other factors also impact whether people flying in airplanes get sick. Sitting near an infectious person, of course, ranks high on the list. Some airlines have voluntarily installed HEPA filters on planes to filter out contaminates in recirculated air, but there's no FAA requirement for the filters, their maintenance, inspection or replacement. While HEPA filters are a step in the right direction, they are not a cure-all, says Murawski, especially because they don't capture gases, ozone or viruses.
Two FAA-sponsored studies are assessing these air-quality concerns and associated health effects. A group of experts convened by the National Academy of Sciences (NAS) is reviewing data on aircraft contaminants and their toxicological effects, and potential approaches for improving cabin air quality, including the replacement of engine and APU "bleed" air with an alternative supply of air. The committee is scheduled to complete its work later this year.
In addition, the National Institute for Occupational Safety and Health (NIOSH) is in the midst of a multi-year study on the transmission of communicable diseases and general air quality in planes. Results of that study are due in 2003.
ASHRAE is also sponsoring two studies to support its development of an aircraft air quality standard. Results from the first study, released in June 1999, found no significant air quality-related health hazards for passengers or crews, but determined that more studies on different airlines and aircraft were necessary before the issue is resolved. In this study, researchers from Consolidated Safety Services Inc. (Fairfax, VA) measured contaminants and environmental parameters and surveyed comfort levels of passengers and flight attendants.
Results of the second study were scheduled for release at ASHRAE's winter meeting in Atlanta in late January and were not available at press-time. This study, conducted by Dr. Niren Nagda, principal investigator at Energen Consulting Inc. (Germantown, MD), identified, quantified and documented potential air supply system contaminants.
Nagda, who declined to comment on his research prior to its release, says that although earlier data has not shown evidence of a link between airplane air quality and human health, certain contaminant—such as semi-volatile organic compounds emanating from engine oil or hydraulic fluid leaks—were not measured in previous studies. Nagda edited the recently released "Air Quality and Comfort in Airliner Cabins," a collection of 15 scientific papers on the topic available from the American Society for Testing and Materials (www.astm.org).
ASHRAE will evaluate results of Nagda's research in its Standard Project Committee 161P, formed in 1996 to write a standard for air quality in commercial aircraft carrying 19 or more passengers. The proposed standard will encompass ventilation, thermal comfort and filtration, and consider chemical, physical and biological contaminants and factors such as moisture, temperature and pressure that may affect air quality. When completed, the standard will be the first to address air quality in airplanes.
The committee has already defined a preliminary minimum outside air ventilation rate of 5 cfm/p, but that definition is back on the table after a restructuring of the committee last year. Murawski, a committee member, says it was expanded to make membership more evenly balanced among interested parties. Committee members now include the airline operators, manufacturers, flight attendants, passengers, academia and government representatives.
Newly appointed committee chairman Dr. Byron Jones says the standards body is in the process of re-grouping, and he doesn't expect a public review draft of a proposed standard until later this year or early 2002. "People need to understand that these are consensus standards, requiring a long and difficult process to develop," says Jones, a professor of mechanical engineering and associate dean for research and graduate programs in the College of Engineering at Kansas State University.
He adds that the 15 cfm/p recommendation for public spaces, just one of the criteria for public air quality defined in ASHRAE Standard 62, was never deemed applicable to air ventilation systems in aircraft and that Standard 62 itself is under review. The 5 cfm/p preliminary ventilation rate proposal for aircraft, which provoked public criticism, is still up for discussion.
"It's too early to speculate on what the recommendation will be," says Jones. Adherence to ASHRAE standard recommendations is purely voluntary, but regulatory authorities, such as the FAA, could impose ASHRAE standards on the industry.
Among the interested parties, debate continues on whether air quality in aircraft is even a problem. But the AFA is convinced it is and would like to see a justification from the FAA for the 8,000 feet cabin altitude limit and a requirement for continuous air monitoring that would determine appropriate ventilation rates. "It's a slow process, but we are optimistic that the FAA appears to be addressing this issue," says Murawski.
If the FAA fails to act, however, there's always Congress. Last year, legislation was introduced in the U.S. House of Representatives that would have established a minimum fresh air standard on commercial flights. But lawmakers decided to postpone action until the NAS study is complete. For now, the question of air quality on airplanes is circling the ground, with no landing strip in sight.