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Aerotoxicity: Toxic air for passengers and airplane crews

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The air we breathe in airplanes has to be pressurized to allow us to survive at the normal cruising altitude of around 10,000 meters, roughly 33,000 feet. No big problem, air can be compressed and heated so passengers and crew can breathe ... but there is a hitch: The compressed air in those airplane cabins has - since about the 60's - been taken from the air that the planes' jets compress before burning it together with the fuel to fly that plane.


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Documentary video: Something in the air


Of course there is no guarantee that this air doesn't contain engine oil fumes - it often does. The thing most people don't know is that there are no filters between the engine and the cabin that could clean the air. Jet engine oil is a highly toxic brew containing organophosphates. Is it any surprise that cabin crew and passengers may suffer from "unexplained" toxic effects called the Aerotoxic Syndrome?

The solution to this problem would be relatively simple - a separate electric airpump/compressor for cabin air, which takes the air from a different place - not from inside the jet motors - but it has not been adopted.

Nexus Magazine had a great article in its most recent edition, which explains why passengers and crew at times suffer from unexplained headaches and other symptoms of toxicity.

The Nexus article is written by Captain John Hoyte, a former airplane pilot who had to stop piloting planes because the toxic effects got the better of him. His health suffered to a point where he could no longer trust himself to safely ferry his passengers from one airport to the other. He is now the chairman of the Aerotoxic Association, a group he founded to make others aware of the problem and to bring about a solution - a much needed change in the attitude of airline executives and airplane makers...

The article is titled Aerotoxic Syndrome - Aviation's Best Kept Secret and is available from the Aerotoxic Association's website.

Here are some relevant quotes:

When jet aircraft first flew in the late 1950s, the engineers knew that they had to provide compressed air in airliners to support life at high altitudes and so they designed mechanical compressors which did the job well. All of the early jet airliners such as the DC-8 and Boeing 707 used this separately compressed air.

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But in the early 1960s, the accountants looked for cheaper, simpler ways to provide that air. It was realised that all jet engines have vast amounts of compressed air available from the forward section of the engine, before the fuel is added and burned.

It wasn't long before they were taking this hot, high pressure air and piping it into the cabin. They would call it "bleed air", as it was "bled off" the jet engine compressor section.

At the time, many engineers warned that if the bleed air should become contaminated with oil from within the engine or hydraulic fluid, then everybody in the jet aeroplane would not be breathing pure air but a contaminated mixture of air and...oil.

However, the risk was thought negligible, such that bleed air quickly became the only way to get compressed air into the cabin of each and every aircraft since that period, including turboprop aircraft where a jet engine drives a propeller.

The fact is that bleed air and oil are allowed to mix due to:

• a basic design feature which deliberately allows small amounts of oil to pass through oil seals to provide lubrication;
• the fact that jet engine oil seals prefer a constant temperature environment to perform "normally" and tend to leak when warming up or cooling down;
• the fact that when power changes are made, such as on take-off or at the top of descent when an incredible number of revolutions are suddenly increased or decreased, there are differing tolerances within the jet and the potential for oil to leak.

There are a number of basic facts which must be presented. There will always be a few minor differences, but the following facts are known:

• aircrew and passengers generally breathe the same air; if the pilot is sick, so will the passengers be sick;
• all jet aircraft use bleed air: turboprops, Air Force One, corporate jets;
• the chemicals in the jet engine oil are extremely toxic, especially since an organophosphate (OP) is added to make the engines last longer and provide fire retardant properties.

What are organophosphates? They were developed during World War II by the Germans, specifically to do harm to human nervous systems. They have since been used in pesticides, e.g., in sheep dip--hence the dreadful neurological illnesses affecting many sheep farmers in the UK during the 1980s and 1990s. Gulf War military personnel were also exposed to OPs and became mysteriously ill.

It is known that chronic exposure to OPs can go on to change personalities and character, affect relationships and moods, and devastate lives.

Breathing organophosphate fumes in a confined space is arguably much more hazardous than breathing in tobacco smoke, and scientists agree that a cocktail of chemicals working together synergistically is collectively many times more dangerous than any chemical in isolation.

Most people would imagine that the oil components would be filtered out, but the incredible fact is that bleed-air lines are not filtered--except, as one lawyer has darkly noted, by the passengers' lungs.

There are filters in the actual aircraft, but not in the bleed-air lines. The aircraft manufacturers helpfully put these filters inside the aircraft to filter the air, but only the air which is already in the aircraft.

Why is aerotoxic syndrome not accepted? It shouldn't be too surprising to know that industry has a habit of working together on certain issues and having vested interests. It could be argued that the aircraft industry starts the problem by designing a flawed system where oil and air can mix. But who is to blame? The engine manufacturer? The airframe manufacturer? The oil industry? The seal manufacturer? The health industry? Definitely not the airlines, although they too are party to the cover-up.

Airlines have a duty of care. At the moment, there are two distinct features: the poisoning and the cover-up. By now, though, we should realise that there are simple technical fixes that could be adopted:

• filter the bleed air;
• fit toxic fume detectors;
• remove OPs from jet engine oil.

It is high time that airline bosses be questioned about a basic duty of care to their aircrew and customers, if only to check that they understand the significance of the emerging, unstoppable science.

While the airline industry and authorities would obviously prefer the "slowly does it", incremental approach, in the meantime an enormous amount of ill health is being misdiagnosed and lives are being wrecked as a systems failure is allowed to go largely
unchecked and airlines give no warnings as to the likely damage or risk which is now known to result from exposure...

Even though you can get the gist from these extracts, I do recommend you read the full article here:

Aerotoxic Syndrome - Aviation's Best Kept Secret

Another video (part 1 of 2) on Aerotoxic Syndrome

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What Captain John Hoyte says is confirmed by a friend of ours who has, for a long time, been employed as a technical support worker in a major airline. Here is what he says:


"Synthetic engine oil is a horrendous poison. All the manufacturers know it, but it is a big big project to modify the world fleet, even if the solution is simple in theory. It would require design, testing, approval, production of material, writing of Service Bulletin etc - and then there is the question of who shall pay for it all. So I do understand (if I can't, of course, support) the manufacturers' stance: better wait till the next generation aircraft..."

In a separate message sent to someone else, our friend hints at his personal experience and gives us an idea of the politics that led to this uncharacteristic inactivity, on what seems to be an important safety issue, by the airplane manufacturers and the airlines themselves:

"I have done some analysis through the year, relating to the problem of air being taken from the engines. In my case the analysis was about "smoke in cabin", i.e. fumes coming in with the air supply, due to leaks in assorted systems in the power plant. What can be said about this aspect is that the engine oils and hydraulic fluids and de-icing fluids that DO enter the ventilation system are all toxic.

I read an article by some professor recently about it. If my recall serves me right he was critiquing research on toxicity - pointing out that there are many compounds involved in these fluids and that the sum total of these chemical impacts (toxicity) had not been analyzed. Whether TCPs (tri-cresyl phosphates) were what he was addressing I don't know.

The industry IS taking it seriously - for the sake of safety. Mainly because these fumes also reach the cockpit, where our good bus drivers do their work. There are many incidents of pilots being mentally and physically affected by such fumes. If it knocks out the pilot, you're on your own back there in the pay-your-way department - without access to a steering wheel. Bon Voyage!

However, the pilots are well aware of the problem, and they do have oxygen masks. So do the passengers, but it is unlikely they would be used unless the fumes were excessive. There are also dual supply/circulation systems, so in case of a leak one can be shut down. That may (or may not) help.

I also know I have read that one or some of the big manufacturers are discussing going forward (not back, of course) returning to outside air supply on future models, with electrical pressurization. The need for pressurization, i.e. compression, is a large part of the reason engine air is used.

Whether the industry has "withheld the truth" is as always difficult to document. What can be said is that the toxic aspect NOW has been well known for a good bit of time, and the manufacturers/FAA has opted NOT to pursue modifications (driven by health concerns), as these would be comprehensive and costly. There is also always the legal question of liability. The FAA (like the FDA) prioritizes the industry, and to hell with the passengers. True: one flight will not kill you, and most people don't fly much, so the risk is small. But if you fly a lot, what are the accumulative risks of this stuff?

Furthermore, of course the supply of NEW air is limited, as the cabin air (mostly) is re-circulated in the cabin, and although there are recirculation filters, they certainly don't sift out all the flying goodies. If you have bacteria/virus-phobia, it is not a good idea to read up on the subject. ... I am not an ATA 21 expert, but definitely aware of the problem.

It would be great if somebody blew the whistle. Our toxic load on this planet is more than high enough as it is without this added exposure. And ... the problem CAN be solved.

Regarding the Dreamliner (Boeing 787) I don't know the ATA 21 system in it. But yes, it is delayed; first flight now scheduled for late June. Regarding the statement that "To launch that plane would have resulted in an admission of a problem", I'd say that is taking it a bit too far. The problem IS known, other solutions ARE being pursued in future (new) aircraft. And of course the reason for that is - among other things - these fumes.

Some links:

"Tricresyl phosphate (TCP) is used as an anti-wear additive in aircraft turbine engine oil"


"Toxic cabin air is more poisonous than reckoned"

(UK parliament - Memorandum submitted by the Independent Pilots Association


Hamilton Sundstrand Delivers First Cabin Air Conditioning Packs for Boeing 787 Dreamliner

"Hamilton Sundstrand's cabin air conditioning packs are the first ever to be electrically driven. Typical cabin air conditioning packs use outside or "bleed" air that enters through the engines to produce the required cooling, but new technologies have enabled 787 engineers at Hamilton Sundstrand to pressurize outside air within the cabin air conditioning pack, reducing overall energy usage while contributing to the aircraft's all-electric design."

Not so Airbus A350 XWB

"For, unlike the Boeing 787, the A350 XBW continues to use bleed air for its air conditioning and anti-icing since, according to Airbus's calculations, purely electrical systems add to the maintenance costs with virtually no cost or weight advantages."


Videos: Unfriendly skies - toxins in airplane cabins
Ever smell petroleum on airliner?

I have and I've never given it much thought.

Now I do.

This is NOT just a European airline problem and as, is too often the case, corrupt government agencies are permitting corrupt corporations to mislead and injure the public.


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So if you are concerned about your own health, or you know someone in the airplane industry or on airline staff, please do let them know that you know about this situation and start making your voice heard. For sure there won't be change any time soon, unless we start to bring this situation - and the fact we know about it - to the attention of those who can take decisions that will make a difference.



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1 Comment

here is a recent article I just came across:

Australian appeal court awards big compensation in toxic cabin air case

The court confirmed the award of substantial compensation to former attendant Joanne Turner for respiratory damage caused by toxic fumes when she was working in a BAe 146 regional jet. Turner has been fighting for this decision since the cabin air contamination event 18 years ago singled out for the this court case.

On 4 March 1992, toxic fumes entered the cabin in the bleed air from the engines during a descent into Brisbane. Since then she has suffered from persistent respiratory problems. The court confirmed the award of A$139,000 ($129,000) compensation, originally awarded a year ago by the Dust Diseases Tribunal. It is to be paid by the insurers of East-West Airlines, which had appealed against the tribunal verdict.

Turner's lawyer Tanya Segelov called the decision a "significant global precedent" for pilots, cabin crew and passengers who have suffered health damage from bleed air fumes in the 146 or other types.

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