Airline passengers and crews who hold poor cabin air quality responsible for nasal irritation and headaches they suffer should, in fact, blame the oils on their skin, hair and clothing for these symptoms.
A new study has shown that interactions between body oils and ozone found in airplane cabins may lead to the formation of chemical by-products that might worsen nasal irritation, headaches, dry eyes and lips, and other common air traveller complaints.
The American and Danish researchers placed two groups of 16 volunteers in a mock-up of an airline cabin, and exposed them to varying levels of ozone and air flow, including levels typically experienced in real flights.
They say that ozone in the cabin increased the production of identifiable chemical by-products such as nonanal and decanal, a pair of aldehyde compounds associated with headaches, nasal irritation and with other symptoms of "sick building" syndrome.
Lead author Dr. Charles Weschler, who is with University of Medicine and Dentistry of New Jersey, says that more than half of the by-products 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, 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 added.
The Federal Aviation Administration says that at cruising altitude, the atmosphere outside of these aircraft contains very high ozone levels, frequently topping more than 500 parts per billion (ppb). However, 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.
The researchers say that most wide-body planes are equipped with ozone-destroying catalysts in their ventilation systems, but 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 on a smoggy day, they say.
According to researchers, their study may 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. Any time you have a situation with high-occupant densities and elevated concentrations of ozone, the same kind of chemistry is going to occur," Weschler said.
The study has been published in the journal ACS' Environmental Science & Technology.