If you are a frequent flyer you may be interested to read here about poisons in the air supply on planes

Christopher Booker's notebook - Sunday Telegraph

See the first part: "Pilots disabled by poisoned air"

Extract:

"The essence of the problem is that the air supply to the cockpits and cabins of many modern airliners is bled off from their engines, where it becomes contaminated with carcinogens, immunosuppressants and highly toxic organo-phosphorus (OP) chemicals, especially a compound known as tricresyl phosphate (TCP) used as an anti-wear additive. Both crew and passengers are thus exposed to small amounts of OPs and a cocktail of other nasties. OPs, more commonly used as pesticides, cumulatively attack the nervous system, causing disorders ranging from nausea, headaches and dizziness to, eventually, serious mental and physical breakdown.

Although this problem was first identified 30 years ago, following a near-fatal incident in the US, it was kept so quiet that when hundreds of pilots in the 1980s began to experience adverse reactions they had no idea why. One of the first to track down the cause was Susan Michaelis, flying BA146s in Australia, when in 1997 she was permanently grounded by severe illness. Two years later, at her instigation, an official inquiry by the Australian Senate heard enough expert evidence to confirm that the cause of so many pilots and cabin crew suffering ill-health was contamination of cabin air by TCP and other chemicals.

In 2001 the cause was taken up in Britain by Captain Loraine, a senior member of the British Air Line Pilots Association (BALPA), who flew Boeing 757s. But from the industry and regulators, such as the Civil Aviation Authority (CAA), they met with a wall of denials. Although more pilots were suffering from "aerotoxic syndrome" every year, there began a cover-up which uncannily parallelled the methods used by government in the 1990s when the health of thousands of farmers was destroyed by OPs in sheep dip."