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The issue of pollution is a daily topic in the modern world, be it from traffic, industry or other sources, but how many of us have worried about the air we are breathing in aircraft?
You may think about the person next to you with a cold but probably not much more than that. People who spend their working lives in aircraft may see it differently however.
For some years now airline pilots have been increasingly concerned about the issue of cabin air quality after some have reported feeling ill, even to the point of incapacitation. The aircraft manufacturers and airlines have always reassured both crews and passengers alike. There can be no inherent problem they say.
Now however, sufficient evidence is available to raise serious concerns and there are two aircraft types that seem to be prone to the problem. They are the British Aerospace 146 (and its variant the Avro RJ) and the Boeing 757, although incidents on other types have also been reported.
The air in aircraft cabins comes from outside where you would expect it to be pretty clean. Fine, but it must be pressurized in order to ensure that the cabin altitude does not exceed 8000 feet. The air conditioning and pressurization system fed by unfiltered compressed air that is bled from the aircraft engines. Theoretically this cannot mix with engine oil due to oil seals.
In spite of designs intended to keep the toxic engine chemicals clear of the aircraft occupants, evidence suggests that this is not always successful. Gas turbine engines – be they jet or turboprop – have some pretty nasty substances flowing through their veins. Any sheep farmer will be aware of Organophosphates (OPs) but may be surprised to know they are creating a health hazard in another, unrelated industry.
If you have heard of OPs it will probably be a few years ago when they produced a major health problem for farmers using sheep dip. Some farmers suffered long-term and serious health problems. OPs can produce symptoms ranging from dizziness to serious brain damage. So what has that got to do with aeroplanes?
A great deal I fear. OPs are used extensively in aircraft engine oil, as are tricresyl phosphates or TCPs. In spite of assurances that it is impossible to mix engine lubricants with cabin air, there are now too many occurrences of contamination for the concern to be ignored.
It is clear that there are two problems here, both the long-term health issues for all who fly and the immediate safety issue of pilot incapacitation. In the past, few cases reported by pilots and cabin crew, have been conclusive, as those affected often recover when they land and display no further trace of illness.
Following more reports of crew, and occasionally passengers, suffering strange effects they have now been attributed to chemical contamination and yet no clear-cut program appears to be in place to resolve the problem.
Imagine that you or the pilot of your aeroplane were to experience, vomiting, difficulty breathing or disorientation. Obviously it is a cause for concern and yet the situation is still treated on a case-by-case basis by the authorities.
In March 2000, both pilots of a BAE 146 en route to Birmingham began feeling unwell. The co-pilot had visited the cabin following reports of an, “oily petrol smell,” and was subsequently unable to concentrate. He soon became incapacitated, leaving the captain to fly the aircraft. Then he too began feeling light headed. This aircraft was approaching its destination and so the captain landed successfully although he found judging height difficult. Both men were taken to hospital where no abnormalities were found.
Subsequent examination of the aircraft found an oil leak that had contaminated the cabin air. As a result of this incident, the UK Air Accident Investigation Branch examined other similar events. The AAIB are the highly regarded crash investigators who reconstructed the Pan Am 747 that exploded over Lockerbie.
They considered 23 other cases of contaminated cabin air and in the majority of cases it was related to defective oil seals, which allowed engine oil to vaporise and enter the cabin air supply. The BAE 146 pilots involved in the Birmingham incident we found to have ingested both decanoic and octanoic acids. These were considered, “irritants,” rather than neurotoxins, although both OP and TCP traces were found in the aircraft systems and cabin. These elements were subsequently deemed to be too small to be a serious threat, although the report does state that people vary in their vulnerability to these agents.
The acids, it seems, can produce headaches and vertigo as well as less serious but unpleasant effects such as eye and throat irritation. One pilot reported having mouth blisters after a contamination incident. In Sweden an entire 146 crew, plus some passengers were affected with a range of symptoms.
Other incidents produced reports of crew and passengers experiencing eye irritation and mouth ulcers as well as nausea, disorientation and in the case of a 757 crew who diverted to Paris, the inability to articulate what their problem was to air traffic control.
The AAIB made a list of recommendations, which were received by the various countries’ regulators with responses varying from partial to complete acceptance. In Britain this resulted in lengthy investigations by a committee whose results were published in language that would do credit to Sir Humphrey of, “Yes Minister.”
The result is to leave the situation unclear. What is certain is that there have been many incidents in which unpleasant chemicals have been introduced into aircraft cabins. Other aircraft types include the Fokker 100 and Boeing 737.
As the AAIB observed in their report, the requirement for aircraft manufacturers is to ensure that the occupants have clean air to breath, yet there is no requirement to ensure that engine oil products are safe.
Some affected pilots insist that there is a deliberate attempt to cover up a threat to the health of passengers and crew alike and there is a growing campaign for action, driven by pilots who have been suffered. The IPA (Independent Pilots Association) complained to the House of Commons Transport Committee that the CAA had a, “head in the sand,” attitude to the problem.
As yet, I have no direct evidence of institutional obstruction but that does not mean it does not exist. During research for my book on the airline industry I definitely see evidence of obfuscation regarding other issues and specifically the problem of pilot fatigue.
Both the airline operators and the regulators – the Civil Aviation Authority – are in denial on that issue, which is clearly too difficult for them to resolve. Bearing this in mind, maybe those who cry, “foul,” over cabin air have grounds for their dissatisfaction too?
In the absence of clear proof, I will leave you with a quote from another famous fictional TV series, “House of Cards”, starring the late Ian Richardson as Prime Minister Frances Urquhart. “You might think that, I couldn’t possibly comment.”
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