Don't blame the airplane's ventilation system the next time you experience dry eyes and headaches while flying.
It's the interaction between your oily body and ozone in the upper atmosphere that is the real culprit, a new study suggests.
The finding, detailed online in Environmental Science & Technology, a publication of the American Chemical Society, could lead to new preventative measures to make flying more comfortable.
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In simulated four-hour flights, American and Danish researchers placed two groups of 16 volunteers in a mockup of an airline cabin and then exposed them to varying levels of ozone and air flow, including levels typically experienced during actual flights.
Ozone in the cabin was found to increase the production of identifiable chemical byproducts, including compounds known to be associated with headaches, nasal irritation and other symptoms of "sick building" syndrome.
More than half of the chemicals produced were the result of the interaction of ozone with bodily oils such as squalene, oleic acid on volunteer's skin, hair and clothing, according to study leader Charles Weschler, a chemist at the University of Medicine and Dentistry of New Jersey.
More study is required to link these chemical byproducts with the adverse health effects flyers frequently report, but if they are "demonstrated to be harmful, simple steps can be taken to reduce their production in aircraft and buildings," Weschler said.
For instance, releasing chemical compounds that destroy ozone in airplane ventilation systems could help remove most of the ozone from incoming air and bring levels down closer to what the Federal Aviation Administration (FAA) recommends.
At cruising altitudes, the atmosphere outside of an airplane contains very high ozone levels, frequently topping more than 500 parts per billion (ppb).
FAA regulations state that cabin ozone levels should not exceed 250 ppb at any time while flying above 32,000 feet or average.
During a four-hour flight that includes cruising at or above 27,000 feet, the FAA recommends that ozone levels should average no more than 100 ppb.
Narrow-body planes are the worst offenders, Weschler said, because they are often not equipped with the ozone-destroying catalysts that are common on wide-body planes.
As a result, ozone in the cabin air of narrow-body planes can "exceed ozone levels in Washington, D.C., on a smoggy day," Weschler said.
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