How good is the air up there? Despite improvements in cabin air quality, questions remain about whether airlines are doing enough to ensure that flying doesn't make their passengers sick

Insight on the News, May 27, 2003 by Jamie Dettmer

Byline: Jamie Dettmer, INSIGHT

Travel through any major international airport in Europe or the Far East today and chances are that a fair number of passengers in the terminals and at the check-in desks will be sporting surgical masks. Board a flight and most of the masks eventually will be removed an example of comfort winning over the fear of contracting severe acute respiratory syndrome (SARS).

For supercautious travelers determined to help resist SARS, the removal of masks once on board their flights may well be imprudent. For despite improvements in cabin air quality during the last decade there still are major questions about the effectiveness of sophisticated air-cleaning systems meant to screen out or otherwise destroy spores, bacteria and viruses on aircraft.

Privately, pilots working for major airlines tell Insight they remain worried about cabin air quality despite the public claims made by their employers that flying is safe and passengers shouldn't fear catching SARS or any other virus for that matter. Some of their anxieties focus not on the newer air-cleaning technology itself, in which they voice general confidence, but on the airlines' reluctance to examine, dismantle and clean regularly the high-efficiency particulate air filters themselves.

Says a senior Alitalia pilot, "The problem is that none of the airlines want to ground a plane for the half-a-day it takes to clean the air systems. A grounded aircraft is losing revenue for the company, so weeks pass before the systems are dismantled and checked. Generally, it is done when the aircraft has to be grounded anyway for other major repairs."

A United Airlines pilot agrees, saying he believes the filter systems should be cleaned after a couple of long-haul flights, depending on how full the planes are. "The filters get real dirty, and most manufacturers recommend regular cleaning," he says, "but from my experience it can be several flights, sometimes a dozen or more, before the cleaning system is stripped down."

Neither pilot, like several others with whom Insight spoke about this problem, was willing to go on the record but both spoke on the condition of anonymity.

SARS has put air quality front and center again as an issue for passengers and flight crews alike. In April, Rep. Peter DeFazio (D-Ore.), ranking Democrat on the House Transportation and Infrastructure subcommittee on Aviation, asked the General Accounting Office (GAO) to study the effects of cabin air quality on airline passengers in light of the emergence and spread of SARS. A key mover of legislation approved by Congress in 1988 and 1989 to ban smoking on domestic flights, DeFazio has written to GAO Comptroller General David Walker requesting an investigation. He notes that air quality in the cabins of commercial airliners has been an ongoing concern for the traveling public for some time. And he emphasizes that "concerns range from general discomfort (e.g., dry eyes, scratchy throats and nasal irritation) and the development of colds after air travel, to more serious concerns about the transmission of disease by other passengers. Concerns about the transmission of disease have been highlighted most recently by the spread of SARS from its origin in Asia to other continents via air travel."

Major U.S. and foreign carriers long have been prickly about criticism of cabin air quality, claiming there is very little risk of infectious disease being transmitted aboard passenger aircraft. They say studies of cabin air quality have not demonstrated a significant health hazard for either passengers or crew and that when compared with the air circulating in homes or office buildings the air quality in passenger jets often is superior.

This issue has been around since the early 1980s, when the carriers set out to increase fuel efficiency by introducing ventilation systems that recirculated cabin air. While older systems had used only fresh air compressed, humidified and cooled by the engines the new systems allow airlines to recirculate as much as 50 percent of cabin air, thereby decreasing workload demands on the engines and reducing the fuel needed to clean the cabin air.

Since then passenger and air-crew complaints about air quality and the contraction of colds and other respiratory illnesses have increased. The airlines have pointed to several studies to back up their claims that all is well with carrier air purity, including a 1999 study undertaken by scientists at the University of California at San Francisco and published in the Journal of the American Medical Association. That study involved more than 1,000 passengers flying between the San Francisco Bay area and Denver during the winter and early spring of 1999. About 19 percent of passengers on planes with recirculated cabin air reported colds a week after their flights. In comparison, 21 percent who flew in planes using only fresh air reported colds.

According to Jessica Nutik Zitter, an assistant clinical professor of medicine at the university and one of the authors of the study, the findings were a surprise. "We were expecting to see an increase in URIs [upper respiratory infections] among passengers traveling on commercial flights that used recirculated air ventilation," she said at the time. Another report cited frequently by the airlines is one issued by the American Medical Association in 1998 and based on several studies conducted by Consolidated Safety Services and the U.S. Department of Transportation. The report found that levels of bacteria and fungi on airplanes were lower than those found in public buildings.