In smaller planes, used increasingly these days, HEPA filter use is much lower, the GAO said. It did not give a rate.
The GAO report, however, did raise health concerns about flying in its report to Congress.
"Although significant improvements have been made to aircraft ventilation systems, cabin occupants are still exposed to allergens and infectious agents, airflow rates that are lower than those in buildings, and air pressures and humidity levels that are lower than those normally present at or near sea level," according to the GAO report.
It said that little is known about the health effects of flying, but it recommended that the cost of placing filters on all planes be studied, noting that they had been "strongly endorsed by cabin air quality and health experts as the best way to protect cabin occupants' health.?.?."
So, what can the flying public do, especially when held captive by a hacker in the next seat?
Most doctors advise against wearing a mask while flying. Masks don't filter out most germs because they're too tiny, Joseph and other physicians said.
But a few common-sense tips can make for a healthier holiday: Try to get enough sleep and eat properly before and during your trip to help your body fight off infection. Drink plenty of water, and wash your hands frequently to minimize the transmission of germs.
Happy -- and healthy -- flying.
Mary Ann Roser writes for the Austin American-Statesman. E-mail: firstname.lastname@example.org
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