Overview of how aircraft cabin air gets contaminated by engine oil fumes, the health effects, what the industry is or isn't doing about it, and the role of the Aerotoxic Association.

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Toxic Fumes in Airliners

Most airliners fly at high altitude where the air is too thin to breathe, and therefore an artificial source is required. In most airliners this is supplied from the compressor part of the engines and is known as “bleed air”. It is cooled to the required temperature and fed into the cabin.

Bleed air comes from a part of the engine which requires lubrication by a specialised synthetic oil. The oil and the bleed air are kept separate by oil seals. Seals may leak and allow oil into the air supply. This may be due to wear over time, faulty maintenance or poor design. “Wet seals” are used, and therefore there is always a small seepage of oil even under the best conditions.

When oil leaks into the hot bleed air, it is known as a “fume event”. Depending on the severity it will be noticed in the cabin by a smell (“oily”, “sweaty socks”, “vomit”, “wet dog”), a haze or smoke. Low-level background levels may be undetectable. There are no air filters between the engine and the passenger cabin.

Jet engine oils typically contains 3% tricresyl phosphate (TCP) which is a potent neurotoxin.

Aircrew and passengers have been diagnosed with chronic ill-health after breathing contaminated bleed air on aircraft, either after a serious fume event or after repeated low-level exposures. The illness was given the name “Aerotoxic Syndrome” in 1999. Symptoms include chronic fatigue, cognitive problems, speech difficulties, breathing problems and other neurological symptoms.

The aviation industry has been aware of this problem since 1977 when a navigator on a C130 aircraft was incapacitated after engine oil fumes entered the aircraft. The issue has been discussed in the UK Parliament for over ten years and the government deny any link to chronic health problems, although independent studies have shown otherwise. The government has chosen to discredit most of this data and conduct its own research which so far has not managed to come to any conclusions.

There are ways the industry could substantially reduce the effects of fume events, for example by fitting bleed air filters, installing contaminated air detectors or by using less toxic oil additives. The new Boeing 787 uses does not use bleed air in the cabin.

The Aerotoxic Association was set up on 18 June 2007 by Capt John Hoyte, a former training captain for a UK airline. Its aims are to help possible sufferers of Aerotoxic Syndrome to recognise their illness, to offer them support, as well as to lobby the industry for regulatory change. John says, “I had Alzheimer-type symptoms of memory loss, crippling fatigue and speech difficulties for 16 years whilst flying the BAe 146 and only found out about Aerotoxic syndrome and other victims by chance. Now science is proving the exact cause. The worrying part is that passengers breathe exactly the same air as the aircrew and continue to be misdiagnosed and mistreated for virus and depression after a ‘fume event’ flight”.


More information:

Aerotoxic Association website  http://www.aerotoxic.org
About Aerotoxic Syndrome  http://www.aerotoxic.org/index.php/about-aerotoxic-syndrome
Government Hansards  http://www.aopis.org/governmenthansards.htm
Victims’ testimonies http://www.aerotoxic.org/index.php/victims-testimonies
Reports and evidence http://www.aerotoxic.org/index.php/reports-and-evidence