EXPOSURE to oil-contaminated air supplies mean air crews are at risk of long-term health problems, a study has found.

In the first paper of its kind, a “clear link” is said to have been proven between a career in the skies and ill-health caused by airborne exposure to engine oil.

Scientists confirmed a cohort of more than 200 aircrew had been exposed to a number of substances through aircraft air systems and reveal a “clear pattern” of acute and chronic symptoms, ranging from headaches and dizziness to breathing and vision problems.

Dr Susan Michaelis of Stirling University, which led the work, said: “This research 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 in normal flight. This is a clear occupational and public health issue with direct flight-safety consequences.”

More than 3.5 billion passengers and 500,000 aircrew are said to have been exposed to low levels of engine oils in 2015 alone. Unfiltered breathing air is supplied to aeroplane cabins via the engine compressor.

Published in the World Health Organisation journal Public Health Panorama, the study is the first of its kind to look in depth at the health of aircrew who are suspected to have been exposed to contaminated air.

Experts conducted independent surveys to review the circumstances and symptoms of crew members working in pressurised flight environments.

One test looked at pilots’ health and showed almost 90 per cent were aware of exposure to contaminants, and around 65 per cent had specific health issues and 15 per cent had died or experienced chronic illness.

The other test looked at specific oil leak incidents, all of which occurred when the aircraft was preparing for, or in, flight. Almost 95 per cent caused symptoms ranging from in-flight impairment to incapacitation and almost 75 per cent included adverse symptoms in more than one crew member, with anywhere between 10 and 23 different symptoms reported in half of events.

Professor Vyvyan Howard, of Ulster University, 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 fliers.

“We know from a large body of toxicological scientific evidence that such an exposure pattern can cause harm and, in my opinion, explains why aircrew are more susceptible than average to associated illness. However, exposure to this complex mixture should be avoided also for passengers, susceptible individuals and the unborn.”