Aerotoxic Syndrome: The best kept secret in aviation?
- Published: 12 February 2010
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Passengers getting off airline flights often experience ‘jet lag’ which is clearly due to changing time zones but many may also experience long-term serious ill health after certain ‘fume event’ flights but will never understand the simple cause. Captain John Hoyte explains the phenomenon known as ‘Aerotoxic Syndrome’.
Three scientists from North America, France and Australia termed this neurological illness ‘Aerotoxic Syndrome’ in 1999 but passengers are mostly still unaware that it is caused by breathing toxic cabin air in-flight.
As an airline pilot, I experienced serious neurological problems in 1990 after I started to fly the BAe 146 four-engined jet on ‘night freight flying’. It left me with Alzheimer’s-type symptoms of chronic fatigue, failing memory, slurred / incoherent speech, poor thought-processing, vision disturbances and countless other mysterious symptoms – not desirable when flying airliners.
I was a very fit young man and I carried on flying. As there are always two pilots in a modern jet I was able to mask it by using checklists and other coping devices, so keeping it quiet out of fear of losing my job.
By 1998 I had become certain that the ‘night’ aspect of my flying was responsible, so I logically transferred to day time passenger flying.
Initially I felt better but would still be troubled by the same symptoms which left me exhausted and feeling intoxicated all of the time. However, I had long since restricted my alcohol intake, as it would quickly send me ‘over the top’.
By 2004/5 and aged 50 I was ready to stop flying as my memory was failing and I felt as though I was going to kill not only myself, but take around 100 passengers and crew with me.
In mid 2005 I had to suddenly stop flying, confused, sick and exhausted. In early 2006 I was grounded with ‘chronic stress’ by expert aviation doctors. A matter of months later I was tested along with 26 other BALPA union pilots and found out we all had highly abnormal blood / fat results but more importantly, measurable sub-normal memories and cognitive dysfunction.
How could jet engine oil be found in my blood and fat? Might it be responsible for the ill health I had learnt to live with but had wrecked my life?
One essential fact is that aircrew, pilots and cabin crew breathe the same air as their passengers. This includes royalty, low cost passengers, politicians and even doctors.
Engine oil and OPs
How might the engine oil have got into my body?
In the early years of jet flying, the Boeing 707 for example had mechanically compressed air pumped into the confines of the fuselage to create the pressure and oxygen content necessary to sustain life at high altitude of jet flying.
But in around 1963 Boeing design engineers discovered that they could use the excess compressed air from a jet engine, taken off the engine prior to the fuel being mixed. This air is called ‘bleed air’ as it is bled off the engine. It is piped, unfiltered into the passenger cabin and is done so to this day.
The engineers of the day warned that if the bleed air should mix with the oil in the engine, it would convey not pure outside air, but an oil / air mixture into the passenger compartment.
Unsurprisingly, the risk was thought negligible and the accountants won the day; it was clearly a simpler system and saved money, yet had an obvious flaw.
In each jet engine seals keep the air and oil apart.
However, what aircraft manufacturers will not tell you is that the oil seals wear out, allowing the oil and air to mix.
Another fact is that jet engine oil is a highly toxic mixture of chemicals but perhaps the most worrying chemical added is 3 – 5 % Tricresyl phosphate or TCP, which is an organophosphate (OP). It is added both to make the engine last longer and as a flame retardant.
OPs date back a hundred years but the Nazis developed them extensively as nerve agents in the 1930s with the intention of damaging the human nervous system.
Many will remember the UK sheep farmers of the 1980s and 1990s who were forced by the government to dip their sheep in OPs but then found that many of the farmers developed sudden mysterious neurological ill health and suicides.
Typical symptoms of OP poisoning are chronic fatigue, sweating, speech difficulties, confusion, depression, respiratory and digestive problems. Even worse, personality and character changes also result from prolonged exposures. In fact, as the OPs affect the central nervous system, all of the body’s major systems are affected, including the brain.
The main route of poisoning is by inhalation. Occasionally oil fumes find their way into the cabin and are reported as ‘vomit’, ‘wet dog’ or ‘inside of trainers’ smells. If a whiff of fumes is smelt, no lasting damage should arise, but anybody being repeatedly exposed to the fumes or for many hours should definitely worry for their health.
Often there is a ‘fume event flight’ where visible oil fumes can be seen in the cabin. There are no chemical detectors on board, so it is up to the aircrew to detect the fumes with their noses and to deal with it by isolating the faulty bleed air line.
Most people will know the dangers of tobacco smoking and that breathing smoke fumes is harmful. The doctors also have a good understanding of the damage done by tobacco smoking and it was as recently as the 1950s that the Government actively supported smoking as being ‘healthy’.
Compare this to the situation in a fume event in an airliner.
There is no official risk, no acknowledgement of the ill health caused but total denial of the long-term effects.
Many aircrew have lost their flying medicals over the past 40 years; the official numbers are deliberately kept low whilst aviation doctors who are paid by the airlines, prefer to turn a blind eye to the cause and are possibly better at wealth than health.
Meanwhile neurological illnesses such as Chronic Fatigue Syndrome (CFS), Parkinson’s, Alzheimer’s, Motor neurone disease (MND) and Multiple Sclerosis (MS) are increasingly found worldwide but researchers state that they ‘do not know the causes’ despite millions of dollars of research.
As I suddenly found myself out of work in 2006, I began the process of finding out the reason.
It wasn’t long before I realised that there were many other victims like me around the world.
There would never be two people with exactly the same symptoms as everybody has different genes and has had different exposures.
The Aerotoxic Association was launched at the Houses of Parliament in June 2007 and has since built up a large network of victims all over the world.
In 2007 government research agreed that short-term ill health could be possible but ‘more research’ was needed to find out if repeated exposures could lead to chronic ill health.
That long-term research is coming to an end now and it is expected that in March 2010 Cranfield University, who have been commissioned by the UK government to do the research, will be in a position to confirm the exact content and concentration of visible oil fumes.
Perhaps when the truth is known, innocent aircrew and passengers will be able to make the link between their ill health and flying. But it is highly likely that yet more research will be called for.
Many suspect that the airlines and governments are keen to cover up this issue as it defines a basic design flaw in all jet-powered bleed air aircraft, including most turboprops, where a jet engine drives a propeller.
Interestingly, Boeing’s latest airliner, the Boeing 787 Dreamliner (which flew for the first time in December 2009) does not use bleed air any more for air conditioning. The designers have reverted back to using electrically-driven compressors supplying outside air. Only a passing mention is made of a ‘more comfortable passenger experience’ and ‘fuel efficiency’ is emphasised, which non-technical passengers can relate to, perhaps more easily.
Passengers may believe that the ‘drop-down’ emergency oxygen masks are for use during a fume event, when the air can suddenly change colour. The pilots only deploy this system when a ‘decompression’ occurs, when the cabin pressure is lost; never because of air quality. The reason behind this is that the oxygen is mixed with ambient air, which is already contaminated.
Some passengers have recently resorted to carrying their own simple activated carbon filter face masks as a ‘better than nothing’ health and safety measure. Whilst others seem happy to put their trust in a flawed design system which experts say goes wrong once in every 100 flights and some pilots suggest happens on most flights, to some extent.
So passengers are reliant on the noses of the flight crew and all too often, as I can testify, they have no idea of the possible harmful effects of toxic air. Young pilots and cabin crew are still blissfully unaware of any danger when they start flying and no risk is said to be present by the regulators, who are directly funded by the airlines.
Pilots are positive, logical people and whilst we can easily identify the problem we are also keen to have known technical solutions introduced, on the precautionary principle:
- Filtering the bleed air is not being done due to ‘cost’ – surely most passengers would agree to pay a little more for clean air?
- Less toxic oil is available - why take a chance with known poisons?
- Toxic air detectors are available – why rely on a pilot’s sense of smell?
There are many recorded instances of passengers being affected by a single fume event flight and where they are still ill, years later. As many passengers never meet again after a fume event flight they will be told by the airline that “They are the only ones to complain……” and any follow up is quickly squashed and lost in meaningless paperwork trail.
The worst effects of OP poisoning can arise several days after the flight, again confusing doctors into misdiagnosing depression or a virus with the subsequent mistreatments.
UCL (University College London) suggested in 2006 that 196,000 UK passengers are exposed per year, that’s about 500 per day.
Perhaps the group of people most affected are aircrew who regularly breathe these fumes but are told it’s normal and not a danger. Many leave the job early, often going part-time before “failing safe” with mysterious, supposedly undiagnosable symptoms.
It is known that some aircrew have not ‘failed safe’ but have, due to their serious neurological problems of failing memory and thought processing, made a poor judgment and paid the ultimate price. There has never been an officially-recorded accident due to Aerotoxic Syndrome but equally Aerotoxic Syndrome is still hotly disputed, ten years after it was first identified.
A high profile, celebrity exposure might be all that it takes to bring in rapid, long overdue changes.
Aircrew often talk of being in a ‘vegetable-like state’, ’zombies’ or ‘permanently intoxicated’.
As they breathe the same air as passengers it shouldn’t be too surprising when frequent flyers develop the same symptoms – the fact that few people have made the link after 45 years is perhaps a measure of how difficult it is to work it out, when people are denied the above information and are sick.
Perhaps the worst aspect of Aerotoxic Syndrome is that there are many innocent people, including young children, who have suffered the dire effects of a fume event but will never make the link to the cause of their long-term serious ill health.
This will hopefully change in the next few months as the media begin to understand a subject and start an open, balanced public discussion which should lead to the known technical fixes being introduced – one day.
Captain John Hoyte, a former commercial airline pilot and BAe 146 Training Captain, is Chairman of the Aerotoxic Association, a support group for sufferers of Aerotoxic Syndrome. Its website contains detailed information on the syndrome as well as news and articles, reports and evidence, testimonies from victims and more details of Captain Hoyte's story.