More than half of the byproducts were the result of reactions with
skin, hair and clothing, according to Charles Weschler, Ph.D., the
study�s lead author, who is with University of Medicine and Dentistry
of New Jersey. These oxidative byproducts are produced when ozone
reacts with squalene, oleic acid and other compounds in natural skin
oils, he said.
�The role of these (by)products in the adverse health effects that
have been associated with ozone is, at present, unknown,� Weschler
said. �If these oxidation products are demonstrated to be harmful,
simple steps can be taken to reduce their production in aircraft and
buildings. For instance, installing ozone-destroying catalysts in
airplane ventilation systems can help remove most of the ozone from
incoming air, he noted.
In 2006, about 750 million people boarded commercial aircraft in the
United States, according to the Federal Aviation Administration. At
cruising altitude, the atmosphere outside of these aircraft contains
very high ozone levels, frequently topping more than 500 parts per
billion (ppb). According to FAA regulations, cabin ozone levels should
not exceed 250 ppb at any time flying above 32,000 feet or average
more than 100 ppb during any 4-hour flight segment that includes
cruising at or above 27,000 feet.
Most wide-body planes are equipped with ozone-destroying catalysts in
their ventilation systems, according to study co-author William
Nazaroff, Ph.D., of the University of California, Berkeley. However,
these catalysts are far less common on narrow-body aircraft. 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.
In fact, the study, which was supported by the FAA and the Danish
Technical Research Council, could help scientists better understand
the adverse effects of ground-level ozone, an important component of
urban and regional air pollution. �Although this work was done in a
simulated aircraft, the results certainly have implications beyond
that,� Weschler said. �Any time you have a situation with
high-occupant densities and elevated concentrations of ozone, the same
kind of chemistry is going to occur.�
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