Contaminated air in aircraft cabins is causing pilots and crew to become sick, a university study claims.

A link between health problems and being exposed to air contaminated by engine oil and other aircraft fluids has been found by researchers working on the study, led by the University of Stirling.

Researchers examined more than 200 aircrew and uncovered a pattern of symptoms ranging from headaches and dizziness to breathing and problems with vision.

One test looked at the health of 219 pilots – 88% who were aware they had been exposed to contaminated air on flights. Almost 65% reported specific health problems while 13% had died or experienced chronic ill health.

Another test looked at 15 oil leaks that had led to symptoms ranging from in-flight impairment to incapacitation.

Almost three quarters included adverse symptoms in more than one crew member, with anywhere between 10 and 23 symptoms reported in relation to almost half the events.

Susan Michaelis, of the University of Stirling’s occupational health research group, told The Times: “This provides very significant findings relevant to all aircraft workers and passengers globally.

“There is a clear cause-and-effect relationship linking health effects to a design feature that allows the aircraft air supply to become contaminated by engine oils and other fluids.”

Vyvyan Howard, professor of pathology and toxicology at the University of Ulster, said: “What we are seeing here is aircraft crew being repeatedly exposed to low levels of hazardous contaminants from the engine oils in bleed air, and to a lesser extent this also applies to frequent flyers.

“Exposure to this complex mixture should be avoided also for passengers, susceptible individuals and the unborn.”

More than 3.5 billion passengers and 500,000 aircrew were exposed to low levels of engine oils in 2015. Unfiltered breathing air is supplied to aircraft cabins via the engine compressor.

Lobby group Global Cabin Air Quality Executive wants equipment in aircraft to monitor air quality.