Airline passengers and crews who gripe about poor cabin air quality could have a new culprit to blame: the oils on their skin, hair and clothing. A recent study suggests interactions between body oils and ozone found in airplane cabins could lead to the formation of chemical byproducts that might worsen nasal irritation, headaches, dry eyes and lips, and other common air traveler complaints. Researchers placed volunteers in a mockup of an airline cabin and then exposed them to varying levels of ozone and airflow, including levels typically experienced in real flights. Consistently, ozone in the cabin increased production of identifiable chemical byproducts including nonanal and decanal, a pair of aldehyde compounds associated with headaches, nasal irritation and with other symptoms of "sick building" syndrome. More than half of the byproducts were the result of reactions with skin, hair and clothing. These oxidative byproducts are produced when ozone reacts with squalene, oleic acid and other compounds in natural skin oils. The role of these byproducts in the adverse health effects that have been associated with ozone is, at present, unknown. If these oxidation products are demonstrated to be harmful, simple steps can be taken to reduce their production in aircraft. Installing ozone-destroying catalysts in airplane ventilation systems can help remove most of the ozone from incoming air. At cruising altitude, the atmosphere outside commercial transports 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 four-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. However, these catalysts are far less common on narrow-body aircraft.