Insufficient evidence to support causal link, but more work needed on cabin fumes, says UK government panel

An independent panel of scientists appointed by the government has rejected claims that organophosphate nerve toxins from engine oil fumes are causing ill-health among pilots. 

Earlier this year, the British Airline Pilots Association (BALPA) presented the UK Department for Transport with evidence suggesting that flight crews exposed to jet engine fumes suffered ill-health including headaches, nausea and chronic fatigue. 

Pilots are exposed to toxins when cabin air, which is warmed across the engine, becomes contaminated by hydraulic fluid, engine oils and pyrolised materials as a result of leaks. Lobby groups believe cresyl phosphate, an organophosphate added to jet oil to cut wear of engine parts, is responsible for the symptoms.

But now the UK Department of Health’s Committee on Toxicity (COT), which was asked to review the data, has concludedthat the evidence to date is insufficient to support a causal link and ruled out further studies to look at organophosphates alone. 

Instead, the committee recommends that cabin air be tested for other ’potentially harmful substances’ and that the ’prevalence of reported neuropsychological symptoms’ be investigated. However, the panel adds that it does not support ’any specific additional research for any other acute or chronic health effect’. 

Sarah Mackenzie-Ross from University College London, UK acted as an independent scientific expert on behalf of the COT. She and her team have clinically assessed 27 pilots who reported symptoms. ’We found all of these pilots to have cognitive deficits and we are in the process of assessing another 1500 pilots,’ she told Chemistry World.

In 2004, the Civil Aviation Authority received only 72 engine leaks into the cabin air supply. But, Mackenzie-Ross suggests that this accounts for only 3.66 per cent of the total because of under-reporting by pilots. ’This could indicate that up to 1967 flights in the UK may have experienced contaminated air in 2004,’ she wrote in a 2006 report.1 

A health scandal? 

Jon Hoyte, chairman of the Aerotoxic Association lobby group, called the conclusions of the COT report criminal. ’The fact that they do not admit that there is a direct link between these fumes and ill health is a scandal,’ he told Chemistry World. ’I was a pilot for 16 years and suffered symptoms including chronic fatigue, dizziness and problems with my speech. It was only when I was assessed in a clinical study that I realised I had been poisoned.’ 

"The fact that they do not admit that there is a direct link between these fumes and ill health is a scandal" - Jon Hoyte

’The government has its hands tied,’ he continued. ’They simply cannot admit a link because this would have severe commercial ramifications for the airlines.’ 

But the committee says that cabin air supply needs to be properly monitored and tested before any links can be fully assessed. 

The DfT has already approached British Airways to set up tests of equipment capable of capturing substances released in fume incidents and says it hopes to begin a study this year.