More and more pilots are reporting that air polluted by engine fumes is making them ill and even incapable of handling their aircraft. So why are passengers not being told? Charles Starmer-Smith reports.

"It was during the descent that my first officer told me he was feeling really bad and very close to vomiting. He went on to oxygen. I felt confused and five seconds later I, too, was close to vomiting. I just managed to put on my mask, after which I could hardly move. We were sitting there flying at 600 miles an hour, late at night, both of us more or less incapacitated. I could not even raise my hand; I could not talk; it was like I was paralysed."

This is not a script for a Hollywood action film but the account of Neils Gomer, a captain on a Swedish aircraft, who was almost completely incapacitated by toxic fumes. He also stated that many of the 73 passengers on the flight were so deeply asleep that it was difficult to wake them up - a fact confirmed by the accident investigator, who noted that passengers were in a "zombie-like condition". He managed to land, but said later that if he had delayed by seconds going on to oxygen the plane would have crashed.

Incidents of contaminated air on aircraft are referred to in hundreds of reports filed by pilots in recent years, and some of the accounts have been seen by The Daily Telegraph. They highlight concerns about the effects of toxic fumes from engines - which some medical specialists refer to as "aerotoxic syndrome". It is not just pilots and cabin crew who are at risk; passengers are too. After examining Civil Aviation Authority records, Dr Mackenzie Ross, a clinical neuropsychologist at University College London, estimated that the problem is affecting up to 200,000 passengers each year. Many campaigners and experts believe that may be a conservative estimate.

Contaminated air in the cabin has long been an open secret among pilots and crews. The aviation industry has been accused of knowing about the problem for decades and doing little to tackle it. With reports linking exposure to contaminated air with long-term harm to health, US lawyers report that passengers and crews are beginning to seek redress.

"Current air travellers are basically the canaries getting knocked down by the fumes first," claims Captain Susan Michaelis, a former pilot in the Qantas regional network and author of the Aviation Contaminated Air Reference Manual (ACARM) - a book that details all known incidents of and studies into aero-toxicity. According to Dr Bhupi Singh, head of research at the RAAF Institute of Aviation Medicine, Michaelis's work is the leading database of factually sourced information on contaminated air in the cabin, yet Michaelis claims it has been ignored by the CAA and the Government. Last month the Government began a study into the subject - the first official acknowledgement that there may be a problem that needs investigating.

The Department for Transport says that it is about to undertake "ground-breaking" research into incidents involving fumes. "The DfT commissioned the Committee on Toxicity (CoT) to examine this issue," a spokeswoman said. "The CoT concluded there was a need to undertake research on cabin air quality involving a strategy designed to look for the largest number of chemicals. The results of this research would be informative for evaluating the potential adverse health effects associated with cabin air fumes."

In 50 of years of commercial flights, aviation has changed beyond recognition. But for all the advances in design, safety and comfort, until the launch of Boeing's new Dreamliner (787) next year (on which air will be compressed electronically), little has been done about the fact that both passengers and crew are breathing in air that comes straight from the engines.

When commercial flights began in 1958 passengers breathed in air supplied directly from the atmosphere using compressors. But this was deemed to be too expensive, so in 1962 a system was installed to draw the air from the heart of the engines - known today as "bleed" air.

Air is drawn out of the compression section of the engine and cooled. It then enters the cabin, where it mixes with recirculated air that has passed through filters designed to remove bacteria and viruses. These "recirculated air" filters do not remove any fumes or vapours from the engine. So if engine oil or hydraulic fuel leaks, because of poorly designed or faulty seals, or even over-filled tanks, toxic chemicals can contaminate the air supply.

At the very least this can cause drowsiness, headaches, flu-like symptoms and nausea - the kind of symptoms that Dr Nicola Hembry, a specialist in environmental medicine, says passengers may wrongly assume have been picked up from another passenger. At worst, air can be laced with a chemical, tricresyl phosphate (TCP), an organophosphate, or other toxic mixtures of chemicals that have been linked to serious respiratory problems, memory loss, neurological illnesses and even brain damage.

Captain Tristan Loraine, a former British Airways pilot of 19 years' experience, has conducted more than seven years of research into the issue since his doctor's diagnosis that repeated exposure to contaminated air had rendered him unfit to fly. His findings, which have been made into a documentary film, Welcome Aboard Toxic Airlines, have prompted an investigation by the BBC1 programme Panorama, which is to be screened on March 3. In 2006 Loraine helped form the Global Cabin Air Quality Executive (GCAQE), a campaign group that represents 400,000 crew worldwide.

Mohamed Bahie Abou-Donia, Professor of Pharmacology and Neurology at Duke University, North Carolina, in the United States, said blood tests are being carried out on airline crews showing the specific antibody that confirms brain damage and cell death. "Those air crew that showed positive results had been exposed to contaminated air in airline cabins," he said.

In Britain, however, the DfT is not yet screening pilots for neuro-psychological impairment related to working on an aircraft. "Until we know what's in the air we can't screen the pilots," a DfT spokesman said. "Once we have carried out air tests we can move on to monitoring pilots for anything that may affect them."

Is there technology available to filter out such toxins? Yes, according to Pall Aerospace, a company that specialises in filtration systems. To install it would cost airlines millions of pounds. Critics say that is why little has been done. But Loraine argues that more significant is the fact that to make the change would be an admission that something has long been wrong. Boeing and Airbus, asked to comment, had not responded as we went to press.

Loraine also says that there are detectors, costing no more than £15,000 per aircraft, that could alert pilots, passengers and crew to toxins in the air. At present, pilots and crew rely on their sense of smell, yet often contaminated air is odourless, which makes the odour filters on some aircraft of limited use.

Nearly all types of aircraft have been affected by contaminated air, but CAA records show that the British Aerospace 146, the Boeing 757, the Airbus A319 and the Embraer 145 seem to be particularly susceptible. Last November it emerged that cabin crew at the no-frills airline Flybe had refused to fly on the BAe 146 after 10 leaks of contaminated air in little more than a year. During a flight from Birmingham to Belfast, two stewards became violently ill and collapsed. The crew was taken to hospital on landing. Flybe said it was "completely confident" that its aircraft are "operated and maintained to the highest industry standards" and added that none of its 700 pilots had refused to fly any of its aircraft. The company said it was phasing out the BAe146 "for green" reasons.

Earlier this month there were serious incidents involving fumes on two British Airways (Boeing 757 and A319) flights to Madrid and Malpensa (Milan). A BA spokesman said: "We can confirm there were reported incidents of fumes on aircraft on February 7 and 11, which were thoroughly investigated. The health and safety of our staff and passengers is of utmost importance to us and we take all reported incidences of fumes seriously. We see no trends in sickness rates or causes that would indicate a link."

In June last year a Qantas crew smelt fumes on the flight deck of a 767 and refused to fly the aircraft. Managers asked another crew to take over and they refused. And, as long ago as 2000, a report to the Australian Senate documented oil leaks on the BAe 146 and outlined how 140 members of Ansett crew held medical certificates from doctors exempting them from flying the aircraft.

A spokesman for BAe said links between contaminated air and health are not yet proven. "It always has been debatable and still is debatable whether contamination due to oil leaks affects a person's health," he said. "This issue was first discussed openly at the Australian Senate inquiry [which] was inconclusive, as has been every investigation since."

CAA documents show that, on British airlines, there have been 25 incidents involving fumes on the Boeing 757 alone since November last year. One pilot complained of being unable to complete his duties; others told of passengers and crew suffering nausea and headaches. The reports mention pilots having to put on oxygen masks, make emergency diversions and mayday calls, and put paramedics on standby.

Malcolm Hooper, professor of medicinal chemistry at the University of Sunderland, said that the travelling public was rarely informed about these events or the possible health consequences. "It's really grossly irresponsible," he said, "and unless we take some serious and urgent action there could be a big disaster."

Engineers are only too aware of the problem. A spokesman for the Association of Licensed Aircraft Engineers (ALAE) said that airlines' desire to cut costs was driving down maintenance standards, which would only make incidents involving contaminated air more frequent.

Michaelis's research suggests that only four per cent of cases are reported. In 2005, for example, her investigations revealed 265 reported incidents of in-flight smoke and fumes on British aircraft - yet a CAA report to the House of Lords claimed there were only 35. Furthermore, 106 BA Boeing 757 pilots she surveyed reported more than 1,660 incidents during their careers, mostly thought to be associated with oil-contaminated air. A similar survey of 250 current and retired British BAe 146 pilots found that 85 per cent believed they had breathed in contaminated air while flying. Over half reported symptoms of ill health relating to air contamination, and nearly one in 10 had to be retired on health grounds.

"There is no way that any working pilot is going to jeopardise his position, so the truth will only come out from retired pilots, crew, engineers and passengers," said Alan Carter, a British pilot of 22 years' experience, who has retired on health grounds. "It is one of the biggest cover-ups in history. If they [airline industry] admitted to this, it would just open the floodgates [for litigation]."

A BAe spokesman said that since 2003 70 per cent of the fleet had been fitted with a new design of oil seal. "Since fitting, we have had no reports of any failures across five million hours of engine operation," he said, adding that, in his view, there was an element of misdiagnosis and misreporting by flight and cabin crew.

Although the CAA continues to deny that there is a health issue or that incidents involving fumes are not being reported, its equivalent in the United States, the Federal Aviation Administration, said in 2006 that it was seriously worried about under-reporting and provided $2 million of funding for further investigation. Chris Witkowski, of the US Association of Flight Attendants, said that in a decade it had recorded more than 800 cases on one airline of flight attendants being affected by contaminated air.

Even when pilots feel compelled to file a report, there is no guarantee that the CAA will receive it. David Hopkinson, a former pilot who had his licence taken away by the CAA for medical reasons (for which he blames toxic air), had filled out a report after a very bad flight on a Boeing 757, and requested it be sent to the CAA. The Daily Telegraph has seen the report, entitled "Toxic fumes on the flight deck". But the CAA claims that it never received it, blaming a clerical error.

When this issue of under-reporting was raised in the House of Lords, the Transport spokesman, Lord Bassam, insisted there was no cover-up, adding that only one in some 2,000 flights are affected by "fume events" and that the numbers of people who report feeling unwell as a consequence are very small. But with 2.4 million flights in and out of Britain each year, that would mean almost 1,200 flights.

"That sounds like a lot of flights," said John Hoyte, a former pilot and training officer for Flybe who is director of the Aerotoxic Association, which was set up to help victims of contaminated cabin air. "We are getting reports of pilots whose memory is suddenly shot to pieces and there is no way they can be in command of an aircraft moving at 600mph. There are several in-built safety factors in a cockpit, so another pilot can take over, but what if two get affected simultaneously?"

Judith Murawski, an industrial hygienist and co-chairman of the Global Cabin Air Quality Executive, is aware of even more alarming incidents. "On one A320, the airline's maintenance records confirm that oil contaminated the air supply. The pilots were both on oxygen and managed to land safely. All three flight attendants have been off work since then with neurological problems - that was 18 months ago. I bet nobody contacted the passengers to check they were OK."

A British family who flew to Florida last summer believe they suffered from air pollution. "We got very ill," said Samantha Sabatino. "The only thing I remember about the conditions on the aircraft were that it was a little bit musty with a stale sort of smell. Then I realised that all the other passengers had the same symptoms as us - I spoke to more than 40. The only thing we had in common was that we travelled out on the same aircraft and breathed the same air."

It recently emerged that British Aerospace, which makes BAe 146 aircraft, had paid money to two Australian airlines over alleged design flaws in the aircraft leading to contamination of cabin air. The documents, seen by The Daily Telegraph, were signed in 1993 and show that BAe paid East West Airlines and Ansett Transport Industries A$750,000 (£350,000) "as liquidated damages in full and final settlement of any and all claims which Ansett and EWA may have against BAe either now or in the future in respect of oil or other fumes adversely affecting the cabin environment."

Another document shows that a further A$1.2 million was paid by Allied Signal, the engine parts manufacturer, to both airlines. Both pay-offs contained clauses that prevented details being made public.

A BAe spokesman denied that any cover-up took place. "Both airlines were unhappy about cabin smells in the BAe 146 and had spent money to investigate the causes. There was no suggestion at the time that the smells had any potential health implications. This was a commercial agreement to compensate the airlines for these issues and the use of the confidentiality clause is standard in our contracts."

During a year-long Senate investigation in the Australian Parliament in 1999, airlines and aircraft manufacturers denied that the chemical tricresyl phosphate (TCP) had ever been present in the cabin. Dr Dai Lewis, chief medical officer at Ansett Australia, told the inquiry: "The chemical that everyone is worried about and surmising is the cause of the problem has never been recorded in an aircraft." Yet a report emailed two years before by the engine manufacturer (Allied Signal) to all senior staff at Ansett, including Dai Lewis, clearly stated otherwise: "TCP is being detected by health and safety measurements during and after pack burns. Levels measured on the bleed air contamination monitor during pack burn were four times greater than we allow."

In Britain, the Department for Transport also claims that it has no knowledge of TCP being found in pilots' blood. Yet the results of tests on a BA pilot, conducted by Glasgow University's Department of Forensic Medicine, were positive and were sent to the CAA.

In 2002 the US National Research Council recommended that airlines do swab-testing after incidents involving contaminated air, so that we can better understand what contaminants are present. No airline appears to have taken that advice. Air crews in Europe, Australia and the US have covertly taken swabs from the walls inside commercial airliners and in 37 cases out of 43 found traces of TCP.

Dr Mackenzie Ross's evaluations of the mental health of 27 pilots who mainly flew Boeing 757s and BAe 146s showed alarming degeneration in reaction times, decision-making and problem-solving abilities. In May 2006 she sent a report of her findings, which mirrored research relating to Australian pilots in 2002, to the Department for Transport. The Government has since agreed to fit air-monitoring equipment on aircraft. It admitted there was a "large body of anecdotal and descriptive evidence" linking ill-health among crew with poor air quality, but said more work was needed to establish a definite link. "The DfT takes passenger and crew health very seriously," a spokeswoman said. "However, it is not known what, if any substances, are in cabin air. That is why it is undertaking this research as a matter of priority."

Ms Michaelis has accused the DfT of being selective in sourcing its data and in the type of tests it is using.

A spokesman for the British Airline Pilots Association (Balpa) said that it welcomes the Government's investigation.

Mobil, whose Jet II engine oil is used in about half of passenger aircraft, despite being deemed to be "harmful" by the Australian Civil Aviation Safety Authority, says there is no acceptable alternative. But a French company, NYCO, claims it produced a different oil lubricant 30 years ago, after the French Health Ministry made it aware of the toxic nature of TCP. This oil has already been validated for a wide range of passenger aircraft.

Peter Jackson, chairman of the UK Independent Pilots Association, said the aviation industry has been aware of the dangers of contaminated air for almost as long: "When an accident finally occurs, if it has not already, they cannot say they were not warned. There is a paper trail a mile long."

* Additional reporting by Mark Rowe.

* Welcome Aboard Toxic Airlines ( will be showing on March 9 at Richmix Cinema, London (, and on March 16 at the Phoenix Picture House, Oxford (
* More information:;; .