Did engine bleed air kill a pilot?

At least one researcher is convinced that aircraft engine “bleed air” used to pressurize the cabin and maintain various systems in flight is highly toxic and may be responsible for the death of a British Airways pilot in 2012. Senior first officer Richard Westgate passed away in December 2012 after flying commercially for 16 years. His illness was a drawn out one, with symptoms such as numbness and memory loss but more than a dozen doctors failed to come up with a solid hypothesis on the cause or a course of treatment. Enter Professor Mohamed Abou-Donia, a leading authority on organophosphate poisoning based at Duke University.

Image of damaged brain tissue courtesy of the Westgate Foundation

Professor Abou-Donia is completely convinced that, based on specialized tests he’s run and also on review of autopsy results and brain scans, the atomization of oil from the engine leaking in to the bleed air and circulating in the cabin contributed to the illness and eventual death. In a research report released this week Abou-Donia suggests that the makeup of these lubricants causes the illnesses and deaths.

Brain and spinal tissues exhibited axonal degeneration and demyelination. Peripheral nerves showed Tlymphocyte infiltration and demyelination. T-lymphocytes had infiltrated the heart muscle tissue…. Damage to the nervous system was consistent with organophosphate-induced neurotoxicity (OPIN). The results also showed that exposure to organophosphates rendered the nervous system and heart tissue sensitive and predisposed to further injury.

And if that isn’t scary enough the researchers go on to remind us of all the chemicals which are near the bleed air supply during a flight:

The engine lubricating oil contains tri-cresyl-phosphate (TCP). The oil also contains n-phenyl-1-naphthylamine, alkylated diphenyl amines and phenol dimethyl-phosphate. The air is also contaminated by hydraulic fluid, which contains tributyl phosphate (TBP), dibutyl phenyl phosphate (DPP), or butyl diphenyl phosphate (BDP). These are all toxic and some are neurotoxic.

So, why aren’t more people suffering from these symptoms? One reasoning offered up is that the susceptibility to the effects is significantly affected by genetic variability. In other words, some people are more likely to feel the impact than others. That reads to me a bit like an allergies issue, though this version can develop over a long term aggregate exposure rather than only in an acute incident.

It would seem, based on this knowledge, that the Professor would have some means to describe which specific genetic markers/indicators are responsible for the increased impact of the aerosolized chemicals but that part is missing, at least from the version I’ve seen online. Or maybe they just know that some are likely to react worse but they haven’t figured out how to test for that yet.

The whole thing is a bit spooky, to be sure. But I’m not going to change my flying habits based on this one.

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Seth Miller

I'm Seth, also known as the Wandering Aramean. I was bit by the travel bug 30 years ago and there's no sign of a cure. I fly ~200,000 miles annually; these are my stories. You can connect with me on Twitter, Facebook, and LinkedIn.


  1. “These are all toxic and some are neurotoxic.”

    Everything is toxic. Toxicity is just the degree to which something damages an organism. Even water can be toxic if you drink too much. All the poisons put on crops to kill weeds and insects are presumed harmless to humans not because they don’t kill things (they do) but because the amounts that remain are so minor they shouldn’t be a threat to us.

  2. @scottrick – Indeed most everything is toxic (noble gases possibly excepted), the question is whether or not exposure to the levels found in a commercial airliner over the time period described are toxic. The study doesn’t say (I doubt enough data on these things in combination even exists to draw a conclusion), so I don’t think we should be dismissive of that possibility, especially given the multlifactoral nature of the problem.

  3. You lose either way. If the bleed air is has impurities that are not good for you, the recirculated cabin air is full of germs, bad odors, and is oxygen depleted.

  4. Conversely, there are actually lower levels of dihydrogen monoxide in the air at altitude, a dangerous compound found in nearly all cancers and diseased blood vessels on pathology.

  5. The answer to your headline is “NO”.

    This man may indeed have died of some strange chemical-related immune disorder or toxicity, but implying it was due to bleed air simply because he was a pilot is drawing a conclusion that isn’t warranted. Organophosphates are pretty common. He may have been spraying his yard with herbicides or insecticides incorrectly for years and been exposed that way.

    There are literally hundreds of thousands of pilots and millions of cabin crew worldwide flying every day. If bleed air were a significant danger, I’d expect this to show up in many people, not just a single individual. If there’s only a single case report out of the millions of crew with decades of exposure each, I’m pretty sure the exposure during my one hour commuter flight isn’t going to kill me. Poor maintenance and pilot fatigue are much greater risks, although the drive to the airport is still by far the most dangerous part of the whole trip.

  6. From an ex-AS MD-80 Captain:

    The MD-80 used to have a nifty little pathway to ‘fume events’ – if the APU developed an oil leak, the fluid would drain out of the the tail compartment, then down the outside of the fuselage, right into the APU air intake. Voila! Instant cabin full of of toxic fumes! It would coat the interior of the aircraft, requiring the plane to be ‘cooked’ – mechanics would override the temperature sensors to allow the cabin heat to reach high levels for several hours to bake the coating away. I had to refuse one airplane that still reeked of fumes – the mechanics’ noses would become desensitized to the odor so they couldn’t tell it was still there.

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