Do you get sick, experience headaches or eye and throat irritation when you fly? Many fliers do, and in an unscientific way, I've always blamed the airplane's air ventilation system. A look at popular articles on the subject confirms this suspicion. However, there have been many scientific investigations of cabin air quality conducted by credible organizations, among them the National Academy of Sciences and the Department of Transportation, and these gave different results. These studies have found that high efficiency filters and the large quantity of outside air supplied to the cabin maintain good air quality.
So is popular wisdom right, or the government agencies? It turns out maybe neither.
Recently, a new theory has emerged. The cause may lie not in the air quality but in the interaction between your body oil and the increased levels of ozone found in the upper atmosphere. American and Danish researchers placed two groups of 16 volunteers into a simulated airline cabin and exposed them to varying levels of ozone and airflow. These tests showed increased production of certain chemical byproducts associated with headaches and nasal irritation.
More study is needed to link these chemical byproducts with the illnesses commonly reported, but if they are shown to have a direct cause/effect then simple steps could be taken to reduce cabin ozone levels.