Despite assurances from health officials that there have been few instances of SARS transmission on aircraft, even the remote possibility of catching the respiratory disease while flying has rekindled concerns about a somewhat dormant issue: the effects of airplane air on travelers' health.
Although air quality inside the cabin has long been a concern, particularly to flight attendants, the issue has taken a back seat to safety, security and financial solvency in the aftermath of the Sept. 11 attacks.
While those continue to be priorities for the government and airlines, fears about SARS and the fact that it has been spread by travelers--at least, after they land--has drawn renewed attention to the question, should we be worried about the air we breathe for hours inside a jet?
The short answer, according to most independent sources, is that there isn't really enough data to say, which has led to the not particularly reassuring recommendation that more investigation is necessary.
The long answer can be found in a report released at the end of 2001 by the National Research Council, a government advisory group: The Airliner Cabin Environment and the Health of Passengers and Crew. Congress, concerned that other questions about cabin air quality had not been addressed, requested the report as a follow-up to a 1986 council study that resulted in the ban on smoking during domestic flights.
In the latest study, which was financed by the Federal Aviation Administration, a committee of experts was asked to assess the presence of various airborne contaminants on airplanes, evaluate their toxicity and effects on travelers' health and recommend ways to improve cabin air quality. Though the committee did not conduct original research, it reviewed dozens of earlier studies of aircraft air, finding most of them lacking in scientific rigor.
"We came to some conclusions, but we were limited in the judgments we could make by a severe lack of relevant data," said Morton Lippmann, the committee's chairman and a professor of environmental medicine at the New York University School of Medicine. In fact, a primary recommendation the committee made was that the FAA provide quantitative evidence that its current regulations are adequate on issues like the amount of ventilation, the maximum cabin pressure allowed and acceptable levels of carbon monoxide, carbon dioxide and ozone in the cabin.
More specifically, it recommended that high priority be given to researching such issues as the health effects of elevated ozone levels that can occur at high altitudes; whether current cabin pressure standards create health risks for infants, pregnant women, people with cardiovascular disease and other "susceptible" travelers; whether using recirculated cabin air increases the risk of exposure to infectious agents; and whether "air-quality incidents" like a hydraulic fluid leak can create health problems.
"Basically, the NRC report looked at the existing research and said more research needed to be done and we agreed with that," said Alison Duquette, an FAA spokeswoman. Toward that end, the agency is preparing to put monitoring equipment on two aircraft and hopes to have some testing completed by next spring, but Duquette said it may be 2006 before testing is completed and it can be determined whether new rules are necessary.
Meanwhile, public attention is primarily focused on the risk of catching an infectious disease while flying (which has not been the highest priority of air quality advocates, who have been more concerned with ventilation and contaminants). Lippmann said that while research suggested there was a "minimal elevated chance" of catching an illness from someone seated next to you and in adjacent rows, "There's virtually no evidence to suggest there's a risk of everyone else on the plane getting sick."
With respect to SARS, Lippmann said heightened monitoring of suspected cases would have turned up evidence if there had been a cluster of SARS infections among passengers. "What air transport does is bring an infectious person to Toronto from China," he said, "But that's a different issue than spreading it among fellow passengers."
That may reassure travelers nervous about flying with SARS dominating the news, but there is still a perception among frequent fliers that the cold they caught after a trip probably originated with a passenger coughing across the aisle. The NRC committee report does not rule out that possibility. "Transmission of infectious agents from person to person has been documented to occur in aircraft," the report states, citing influenza, measles and tuberculosis as diseases with documented cases of transmission on planes.