Regulation may be in the air for the cabins of commercial aircraft, though it is unclear which is more infectious: airborne particles or hysterical legislation. On April 6, the House subcommittee on aviation, chaired by John Mica (R-Fla.), discussed efforts to prevent a pandemic–an epidemic across international boundaries affecting masses–and debated whether the problem can best be addressed through legislation or common sense.
An outbreak of great scale is a concern, given that there are 1.6 billion air passengers each year, and that most of them complete their trip before they show any symptoms of being infected with a particular pathogen. While epidemics planted by terrorists are cause for concern, natural outbreaks can be just as devastating. Between November 2002 and July 2003, Severe Acute Respiratory Syndrome (SARS) killed at least 774 people among the 8,000 suspected to have been infected while traveling on the airlines.
With that in mind, the airline cabin is certainly not the only source of contamination. The common flu kills 36,000 people on the ground in the U.S. each year.
Lawmaking and technical standards about cabin air quality remain in suspension until as late as 2007, when the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) may cough up its analysis of airborne dangers. Congressional committee members sharply criticized Dr. Jon Jordan, the FAA Federal Air Surgeon, for relying on a trade group with a history of delay and no clear experience in aviation.
“At this time, no one takes responsibility for the safety of cabin air at takeoff,” acknowledged Dr. Jordan.
In September 2004, the FAA launched its own airliner cabin environment research, ACER, but despite feverish funding and a half-dozen university partners the agency has been sitting on its hands.
In any case, it may be that the passengers’ hands, not the cabin air, might be the real problem. “It might be more effective to distribute alcohol wipes to all the passengers,” said Vernon Ehlers (R-Mich.). Witness Dr. Ronald Brown, founder of Orlando, Fla.-based AeroClave, agreed.
“It is my belief that many aircraft-acquired illnesses are not the result of recirculating air, but rather the direct hand-to-mouth transmission from touching contaminated hard surfaces.”
Seat belts, tray tables, latches and toilets do the dirty work. Studies by the World Health Organization have shown the SARS virus could live on hard plastic surfaces for 72 hours.
In August, AeroClave will introduce a unit promised to clean a regional airliner-size cabin in 2.5 hours by manipulating air to a temperature and humidity “lethal for a number of disease-causing agents.” AeroClave is completing prototype tests on its two decommissioned DC-9s, saying that each application costs only $100 in consumable fuel and filters.
Cabin Air Quality
A Government Accountability Office survey found that 50 percent of smaller regional commercial fleet operators used high-efficiency particulate air (HEPA) filters, which change cabin air up to 20 times per hour and at 99.97-percent efficiency. Ehlers questioned whether scientists knew enough about spreading viruses to require fleet coverage. Legislators, keeping an eye on research by the Department of Homeland Security and the Defense Advanced Research Projects Agency, are considering requiring bioaerosol detectors with a one-minute reaction time.
Brown and others testified that filtering is widely misunderstood by the public.
“The airflow in (Boeing airplanes) is generally from top to bottom, not front to back as many people believe. Air supplied at one seat row leaves at approximately the same row.” This pattern compartmentalizes the airflow and limits the spread of particles.
Dr. Jordan also defended the air in commercial aircraft cabins.
“It is important to understand that studies have indicated that many aspects of cabin air are as good as or better than the air found in office or home environments. Air carriers have the benefit of flying at altitudes above the air pollution that is circulated into spaces on the ground that we occupy daily,” said Jordan.
Jordan was unaware of studies specific to business jets, adding that findings would differ depending on whether the aircraft recirculated its air and, if applicable, its quality of filtering.
Developing Best Practices
Ground environments such as airports contain large transient populations, and researchers are seeking machines with a shorter detection time, and protocols for communication and treatment. The DOT is compiling a best- practices manual for airport operators at international gateways, though the committee was given no deadline for its completion.
Dr. Anne Schuchat, acting director of the National Center for Infectious Diseases at the Centers for Disease Control and Prevention (CDC), said that the greatest current threats to aviation are pandemic influenza similar to the strain that struck in 1918; the Marburg hemorrhagic fever now consuming Angola; and the Southeast Asian avian or “bird flu” designated H5N1, though it has not yet sustained person-to-person transmission.
There are no FAR or NTSB requirements to report an apparent illness or even a death. The CDC, though, has civil authority.
“In accordance with 42 CFR Part 71.21(b), CDC requires the commander of an aircraft destined for a U.S. airport to report the presence on board of any death or any ill person among passengers or crew to flight control,” reported Dr. Schuchat.
An ill passenger, defined as one with diarrhea or with a persistent temperature over 100 degrees F and accompanied by rash, glandular swelling or jaundice, must be reported to the quarantine station at or nearest the port of arrival. Such individuals can be legally detained.
Before smallpox was eradicated in the 1970s, more than 200 ports of entry held medical staff. Now, just 18 have quarantine stations, though the CDC plans to extend that number to 25 by FY2006, to cover 80 percent of international arrivals. The CDC developed a passenger locator form for scanning into an electronic database, to share with the U.S. ATA, IATA and the World Health Organization, but has no plans for Parts 91 or 135 flights.
“We are concerned about several different migrating populations entering the U.S.,” said Dr. Schuchat, “including international travelers, more than one million annual immigrants and refugees and asylum seekers. Preventing the importation of an infectious disease must address pre-departure, in-transit or upon arrival and post-arrival.”
The CDC manages health alerts in tiers of severity, via written and online travel notices; staffs the GeoSentinel network and TropNetEurope clinics to share its observations; and holds teleconferences with the medical committee of the ATA as often as once per week.
Humans are not the only carriers of airliner disease. Zoonotic infection, transmitted from animals to humans, can appear in healthy-looking live animals, which arrive in the U.S. at a rate of nearly 260 million per year, and animals can be seized under 42 CFR Part 71. The OST is also ridding insects via “non-chemical disinsection,” beginning with a pilot program in Jamaica.
Preparation is good sense, but Dr. Mark Gendreau of the Lahey Clinic Medical Center in Burlington, Mass., testified that there are too many variables to name aviation the bad carrier.
“Insufficient data prohibits a proper analysis to gain an idea of the probability of disease transmission in a commercial aircraft cabin,” he concluded. “The risk is dependent on proximity, chance, mode of transmission, infectiousness of the source, pathogenicity, duration of exposure, and ventilation, humidity and temperature.”
In March the Tufts-New England Medical Center reported that cabin air quality has been the subject of media investigations because of the perception that airborne particles are distributed cabinwide by the ventilation system. The Tufts study concluded that the perceived risk is greater than the actual risk.
“No peer-reviewed scientific work links cabin air quality and aircraft ventilation rates to heightened health risks compared with other modes of transport or with office buildings.”