Planes, Trains, and …Germs?
Travel Health Risks You Can -- and Can't - Avoid
Which Is Healthier: High-Flying Planes or High-Rise Offices?
Air passengers often complain about aircraft ventilation. But Gendreau notes
that a normal airplane cabin changes its air 15 to 20 times an hour. A typical
office building changes its air 12 times an hour.
High efficiency particulate air (HEPA) filters scrub the air on some planes.
The filters may be able to trap airborne viruses because they catch the
droplets that carry the viruses. But 15% of U.S. commercial airliners carrying
more than 100 passengers lack HEPA filters.
"Federal regulatory agencies need to tighten the rules in terms of
ventilation and in terms of the HEPA filters that are used," Gendreau says.
"Now, in the U.S. and Europe, there are no requirements for how much
ventilation an aircraft should have. They don't specify what kind of HEPA
filters to use - or even require them."
Even so, there's no definitive proof linking airplane ventilation to disease
spread. Overall, the risk of catching something from another infected passenger
is about 1 in 1,000 -- about the same as an office building or any other
confined space. And Gendreau points out that mathematical models indicate that
doubling a plane's ventilation rate would cut the risk of airborne infection by
half (using tuberculosis as a model).
Yet airplanes make infection easier in other ways. One example is
pressurized air. Planes normally set cabin pressure to what you'd experience at
the top of an 8,000-foot mountain. Since cruising altitudes are higher than
this, planes cycle air through their engines to pressurize it. That heats the
air, which is then cooled. This wrings out just about every drop of
"We end up with low-humidity, desert-like air," DeHart says.
"The longer you fly, the drier your mucous membranes get. And the dryer
they get, the more susceptible they are to infection. So in a cabin with nearly
500 people, the air is circulated, the air is filtered -- but still, infectious
material gets spread."
Most of that spread comes from the people sitting next to you, and in the
two rows in front of you and behind you. If one of these people has a cold, you
are at risk.
"The risk is higher than your typical office environment, because of the
much higher concentration of people for the air that you have," DeHart
says. "The impact of colds is probably more frequent than you would have in
just an office setting."
Is There a Health Risk From Pillows, Blankets, and Tray Tables?
Germs don't just fly through the air. They also lurk on contaminated
surfaces -- what infectious disease specialists call "fomites."
Gendreau warns that there's a lot of "hype" around this issue. The
facts, he says, don't turn up any obvious dangers.
"There have been a number of microbiological content studies of aircraft
cabin. In fact, the FAA is currently looking into this," he says. "The
British government's aviation health working group recently looked at microbial
flora [germs] in two different aircraft types. They found that this stuff is
not worse - and maybe better - than other places where people congregate like
buildings or other modes of transportation."