Features

Cabin air: Something in the air

21 Feb 2008 by Mark Caswell
The UK government has announced plans to monitor cabin air quality, years after concerns were first raised that air contamination is risking the health of crew and passengers. Katharine Cooke investigates. On the evening of Friday 12 November 1999, Captain Niels Gomer was at the controls of a Bae146 aircraft on flight BU925 from Stockholm to Malmö. As it climbed to altitude both Gomer and the purser had noticed a smell like “burnt sulphur”, which passed away quickly. Then, as he was preparing for landing, Gomer began to feel dizzy. He says: “We were descending and we both felt pretty bad. My first officer said he felt sick and I was leaning forward and thought I was going to throw up over the instruments. I took off my headset and put on my oxygen mask, and that was the last thing I could do physically. The flight attendant came in, but I couldn’t talk or move or raise my hand.” Fortunately the aircraft was still several thousand feet above ground and, after several seconds of breathing into his oxygen mask, the co-pilot was able to take the controls from Gomer and make a normal landing. Friday-night passengers are usually eager to get home for the weekend, says Gomer, but not in this case. “Most of them were asleep. People from the ground service had to come in and wake some of them up.” The final report by the Swedish Accident Investigation Board recorded that the passengers were “passive and more tired than normal”, but that no one had complained. There was no follow-up of the passengers and no medical tests of the pilots. The report concluded: “The incident was caused by the pilots becoming temporarily affected by probably polluted cabin air.” It is well known in the aviation industry that pollutants can enter cabin air. Modern aircraft supply their cabins with air drawn from the engines known as “bleed” air. If a seal inside the engine is not secure, oil or hydraulic fluid can leak into the bleed air, which passes unfiltered to the cabin. The heat of the engines breaks down the oils and fluids into chemical fumes which have been described variously as smelling like “dirty socks”, “wet dog” or acrid, burning oil. Former pilot John Hoyte flew the Bae146 between 1989 and 2005 and believes that repeated exposure to these “fume events” caused him progressive health problems. He began suffering speech difficulties, poor memory and chronic fatigue, and eventually lost his licence in February 2006 with an official diagnosis of chronic stress – but not before he had to walk off the plane on three occasions because he felt unsafe to fly. He says: “I lost my thought processes and got brain fog – it’s like being intoxicated.” In June last year, Hoyte and fellow pilots launched the Aerotoxic Association to push for the condition to be recognised as “Aerotoxic Syndrome”. He says: “We want an acknowledgment that if you sit on a plane full of toxic fumes caused by a broken engine seal it won’t do you any good.” Hoyte is worried that passengers may also be suffering symptoms but going undiagnosed. The Bae146 aircraft (pictured) has one of the worst reputations for fume events: it was reported in October that several Flybe staff were boycotting the Bae146 after a spate of fume events had incapacitated air crew. Flybe is now withdrawing its Bae146s from service, although it says that this move is commercially motivated. In a statement, the carrier said: “Flybe took a commercial decision several years ago to reduce the number of aircraft types operated from three to two. As a result the Bae146 fleet will have been withdrawn by March 2008.” The Bae146 was also at the centre of a House of Lords debate in October when Lord Tyler claimed that in 1993, BAE Systems paid A$750,000 (£343,000) to two Australian airlines in return for suppressing concerns about design flaws in the Bae146 that were causing air contamination. Figures from the Civil Aviation Authority (CAA) state that between January 2001 and April 2006 there were 262 reported fume events, of which 38 per cent took place on the Bae146 or the B757. In the last seven years there have been 18 reports of smoke or fumes entering the flight deck in which “incapacitation” of members of the flight crew occurred. But former pilot Susan Michaelis, who works for the Global Cabin Air Quality Executive (GCAQE) and has been researching air contamination for 11 years, believes many fume events go unreported – dismissed as a nuisance or an everyday part of flying. GCAQE reported a survey of 242 past and present Bae146 pilots in which 86 per cent had experienced fume events and 57 per cent had experienced adverse effects. Michaelis says: “There is real ill health going on – both short and long-term. We hear from crews that 8 per cent are failing their medicals: that’s a huge number.” A British Airways spokesperson told Business Traveller the carrier had found no evidence of under-reporting from pilots: “Our internal reporting requirements are far in excess of the legal requirements and we have no indication that our pilots are reluctant to report fume events.” So far no link between fume events and chronic health problems has been acknowledged by the industry. The CAA says: “While there is no doubt that fume events occur [the question is] whether there is any link between them and long-term health effects. There is as yet no medical evidence to support that.” In 2005, under pressure from pilots’ union BALPA to investigate the issue, the Department for Transport (DfT) asked the Committee on Toxicity (COT) to review the problem. In September 2007 the COT reported that it was “not possible to conclude … that there is a causal association between cabin air exposures and ill health in commercial aircraft crews.” Sarah Mackenzie Ross, a clinical neuropsychologist at University College London, was one expert who submitted evidence to the COT. Mackenzie Ross, who has previously worked with farmers poisoned by organophosphates in sheep dip, studied 27 pilots with health problems after reporting exposure to fume events and put them through neuropsychological tests. Nine of the pilots were excluded from her results due to previous medical problems that might have accounted for their symptoms, but she was left with 18 pilots “in whom we could find no explanation for why they were ill”. She also found that their cognitive problems were similar to those suffered by farmers exposed to organophosphates. When 20 of the pilots underwent blood and fat analysis, all were found to have higher than average levels of one or more volatile organic compounds in their tissues, and three tested positive for tricresyl phosphate (TCP), a toxic organophosphate which is an ingredient of jet engine oil. The COT didn’t accept Mackenzie Ross’s findings as proof of a link between pilots’ ill health and contaminated air – and Mackenzie Ross acknowledges that it was only a small “self-selected” sample. She says: “I can demonstrate an association but not absolutely prove it. But what I said to the government was that you shouldn’t have a relatively young group of pilots who have cognitive impairment – they have been screened to be fit and healthy.” Michael Bagshaw, professor of aviation medicine at King’s College London, says he is unconvinced of a link. “There are more than 20,000 pilots on the CAA database and as far as I know there are only 18 pilots who have these symptoms. These 18 pilots complain of a wide range of symptoms. The Aerospace Medical Association and other organisations have looked at these symptoms and said you can’t make a case for a particular syndrome – they are too diverse.” He is also cautious about drawing comparisons with sheep dip: “The farmers who have been affected by organophosphates were standing in baths of the substance getting huge exposure.” He also emphasises there is no reason for passengers to worry: “I’m not aware of any passengers complaining of any symptoms.” The COT has recommended further research to find out what chemicals are released in a fume event, and a government monitoring project began late last year to try to capture air quality during one of these events. But it also concluded there was not enough evidence to justify looking specifically for organophosphates in cabin air – a decision which baffles the former pilots, who believe the Government wants to avoid finding TCP to protect the aviation industry. The GCAQE submitted a detailed response to the COT’s provisional findings, listing cases where TCP has been found in aircraft, including the Bae146 involved in the Swedish incident, and in swabs taken by cabin crew on various aircraft between 2005 and 2007. Toxicologist Chris Van Netten, from the University of British Columbia, confirmed to Business Traveller that he had found TCP in samples taken from aircraft filters, flight deck walls and a pilot’s uniform. Clement Furlong, a toxicologist at the University of Washington in Seattle, says genetic factors make some individuals more susceptible to organophosphates than others, which means some pilots who have been exposed to TCP may suffer much more severe symptoms than others. He is devising a blood test to detect TCP. He says: “You need several blood samples from an individual – one shortly after the event and then several over a few weeks – and you could look at different biomarkers and extrapolate back to find when the acute exposure occurred.” Tests on the Bae146 involved in the Swedish incident found more than 90 different chemicals in the engine bleed air. None of these was above its individual exposure threshold, but as Susan Michaelis points out: “Exposure standards are ground-based standards – they are only listed for certain chemicals, are arbitrary and not generally updated.” She adds that the Aerospace Medical Association, among other organisations, has recognised that ground-based exposure standards should not be applied to aircraft cabins. Exposure standards also fail to consider exposure to multiple substances. Sarah Mackenzie Ross says: “People get preoccupied with one chemical but it’s more to do with the mix of chemicals. We know from the pesticide world that if you’ve had prior exposure to one chemical it may have destroyed the enzymes needed to detoxify the effects of [exposure to] the next one.” Furlong says TCP can knock out the body’s ability to cope with other chemicals. “TCP or its metabolite will whack your carboxyl esterases, [enzymes] which are very important in metabolising pyrethroid compounds that are sprayed in aircraft in some countries to kill certain insects.” As well as onboard monitoring, the COT recommended that the Department for Transport commission a large-scale study comparing health and cognitive functioning in pilots flying different types of aircraft. When Business Traveller contacted the DfT it was unable to confirm if it would fund such a study – a spokesman said it was focusing on the onboard monitoring first. He admitted it would be a “slow process”, but added: “We haven’t ruled out anything in the COT report but we’re taking it stage by stage. We agree with everything they say.” Meanwhile, ex-pilots are concentrating on raising public awareness. One, Tristan Loraine, has funded and directed his own documentary, Welcome Aboard Toxic Airlines. He says passengers are entitled to know when a fume event has occurred. “My concern as a pilot has always been that I have stood at the front of the plane, having used an emergency supply of oxygen, and watched all these people walk off. Some people may be fine but others might not be.”There is hope in the form of the new B787, which Boeing says draws its cabin air from outside instead of from bleed air. In a statement to COT, Boeing said: “This architecture eliminates the risk of engine oil decomposition products being introduced in the cabin supply air in the rare event of a failed engine compressor seal.” Loraine says: “We’re not saying don’t fly – we’re saying people should be told [when they are exposed]. We’ve been telling the industry for 10 years and they’ve done nothing – now we have to play the last card, which is telling the public.” Business Traveller was unable to find a spokesperson to respond to comments on the COT report, despite calling the press offices of the Department for Transport, Department of Health and the Food Standards Agency. WEBSITES Aerotoxic Association aerotoxic.org Global Cabin Air Quality Executive gcaqe.org Committee on Toxicity cot.food.gov.uk Toxic Airlines documentary welcomeaboardtoxicairlines.com Aviation Contaminated Air Reference Manual - susanmichaelis.com
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