Government departments in the UK and USA seem to be on the verge of making a U-turn on whether heated oil fumes in aircraft cabin air can severely damage crew and passenger health. Having previously denied it, now they seem to be preparing to admit the possibility.

Meanwhile, some airlines are fitting air treatment systems to clean up engine bleed air supplied to the cabin and teaching pilots handling techniques to reduce the number and severity of fume events.

Lufthansa CityLine is in the vanguard among airlines tackling the problem in its BAE Avro RJ85 fleet. The RJ85 is one of the BAe 146 series aircraft with a poor record of fume events, a fact established by the Australian Senate in 2000. CityLine has devised engine-operating techniques to reduce the number of incidents. Cargo carrier DHL also provides its crew with similar instructions for its Rolls-Royce-engined Boeing 757 fleet, which too has a relatively poor record with fume events. But whereas Lufthansa encourages reporting of incidents, DHL has advised its pilots that the occasional fume event is "normal".

 © AirTeamImages
Cargo carrrier DHL provides engine operating advice for its Rolls-Royce-engined 757s, which have a poor record with fume events

The "fume" or "smell" events occur when oil seeps from faulty engine oil seals into the compressor bleed air used to ventilate and pressurise the cabin. The air is heated in the compression process, turning the oil into aerosol particulates and fumes that are inhaled by crew and passengers. Anti-wear additives in aeroengine oil contain organophosphates that are neurotoxic if heated and inhaled. Organo­phosphates that could come into contact with humans are banned in other industries for health and safety reasons.

But although government agencies now admit that neurotoxins - for example isomers of tri-cresyl phosphate - are present in these fumes, they claim their quantities pose no threat to health. But they admit they do not know in what concentration or form (vapour or droplets) the chemicals are present.

In a re-released frequently asked question list about "cabin air quality" on its website, the UK Department for Transport now says: "The evidence available did not establish a link between cabin air and pilot ill-health, but nor did it rule one out."

It adds: "Some pilots who have experienced these events report a variety of short- or long-term symptoms or ill- health. But it is not certain that these symptoms are work related." This avoids mention of the hundreds of pilots all over the world, recorded by the Global Cabin Air Quality Executive (GCAQE) and the Aerotoxic Association with symptoms of serious long-term sickness from organophosphate poisoning that went undiagnosed for years because pilots and most doctors did not know about it. The DfT does not mention cabin crew, who have also suffered.

Explaining its current inquiry, the DfT says: "The Committee on Toxicity and the House of Lords Select Committee on Science and Technology have identified a knowledge gap. We are now trying to fill that gap. No-one has previously captured samples of cabin air during normal conditions and fume events and analysed them to see what substances they contain and in what concentrations."

Meanwhile, as the principal researcher for the GCAQE Susan Michaelis points out, there is a massive body of scientifically gathered evidence available to the DfT, but it is selective about the information it chooses. Michaelis was refused entry to a recent Aviation Health Working Group meeting.

Since then the Aerotoxic Association has called for the resignation of the chairman of the UK AHWG Sandra Webber, on the grounds that she has been colluding with British Airways' health services head Dr Nigel Dowdall to "counter the impact of lobby groups" on the fume and health issue. Dowdall also holds a senior position at the DfT. Flightglobal has seen Dowdall's letter to Webber, but BA has not replied to an invitation to comment.

The Countess Mar is a member of the UK House of Lords and has campaigned for the recognition of organophosphate poisoning among sheep farmers contaminated by sheep-dip. Her address to the annual GCAQE meeting in May 2008 described the typical behaviour of government and the scientific establishment when the status quo is challenged: "Since 1992 I have campaigned to have [organophosphates'] toxic effects recognised, and I have been through the [familiar routine]: 'It is perfectly safe', then - 'if it is making you sick it must be your fault', followed by - 'well, there may be a little problem, but we need to look into it scientifically, taking as long as we possibly can by being as devious as it is possible to be'. There was once a time when policy was made to fit the science. With changes in research funding provision, science is now more and more often manipulated to justify the policy."


Meanwhile, BAE is promoting a new bleed air treatment system, AirManager, but does not, in its publicity material, explain why it is needed. Lufthansa CityLine, which has fitted the system in some of its RJ85s, says that it seems to make the problem worse.

Lufthansa said in January that it had decided to accept the equipment without testing it, because it was so keen to neutralise fume events. And the equipment had been approved by BAE and the European Aviation Safety Agency.

Lufthansa added: "Shortly after the modification of a further three aircraft, an increase in smell events was noticed, especially in the modified aircraft. Therefore we have to question the effectiveness and reliability of the new filters. As we have encountered problems we have decided to discontinue the modifications for the moment...The already modified aircraft will continue to fly with the new filter system. [But] the air treatment system of D-AVRG, which experienced an increased number of smell reports after modification, has been de-installed and replaced with the old filter system."

The airline has also advised on engine handling technique to reduce fume events: "The labyrinth seals [in the engines] operate pneumatically and there is a time delay. If an engine spools up from idle to take-off thrust, first the oil pressure has to increase before the seal closes completely. So it is possible for a small quantity of oil particles to enter the air conditioning system. By applying the thrust increase more slowly the seals will have time to close."

To give the auxiliary power unit oil seals time, Lufthansa reminds pilots to wait 2-5min after APU start-up before opening the APU bleed air supply to the air conditioning system.

By contrast, an EASA A-NPA is considering whether cabin air quality management needs regulating. The UK Civil Aviation Authority says fume events can be dealt with by instructing pilots to don oxygen masks immediately, and that it is not its duty to protect the health of cabin crew or passengers. The CAA and the UK Health and Safety Executive effectively disagree over which has responsibility for the enforcement of health and safety standards on aircraft - so no-one in the UK is overseeing it.

In her submission to EASA on behalf of the GCAQE, Michaelis says: "The content of the A-NPA is of concern as it shows an appreciable lack of understanding of the currently available data on the subject, and a significant industry bias. Given that contaminated air is an airworthiness issue this, of course, is a major area of responsibility for EASA." The A-NPA finally concedes: "If deemed necessary, a rulemaking phase could be launched to create new airworthiness standards to limit as much as possible the occurrence of this kind of event."

Michaelis' submission includes an eight-page appendix of referenced studies, academic publications and scientific inquiry findings, all addressing the issue of contaminated cabin air and the associated hazards to crew and passenger health. There are 168 studies and inquiry findings listed. Michaelis has also sent EASA her book, the Contaminated Air Reference Manual. But EASA says studies should be pursued as if nothing has been established. The UK Committee on Toxicity has taken the same line, as has the UK DfT. No action is to be taken as a result of existing knowledge about the health dangers of organophosphates.

Surprised that no aircraft has cabin air contamination detection and warning systems, the standards-setting American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) has sent this statement to the Federal Aviation Adminstration, EASA and the International Civil Aviation Organisation: "Still, no aviation regulator requires either bleed air monitoring or bleed air treatment.

"To this end, the ASHRAE writing to ask you to establish a joint independent committee this year to investigate the technical implications and flight safety benefits of addressing bleed air contamination, and to determine the requirements for bleed air contaminant detection systems and solutions to prevent bleed air contamination, as described." By contrast, submarines, spacecraft and mines have contaminated air detection and warning systems.

Publication of an ongoing DfT-funded study of fume events was expected by May, but that date may have slipped. Five unnamed airlines flying 146 series aircraft and 757s are involved, and about 100 flights with each are to be tested.

The anticipated collection of 100 samples "showing not only presence but concentration of substances" is interesting, because if the original DfT statements about reported fume events occurring about once in every 2,000 flights are correct, 500 flights would not produce 100 samples.

The original target was to have completed sample collection by February/March, and peer review was to be complete by May, but there has been no confirmation that this has been achieved.

The changes in the past two years are small but significant. There is no longer denial that fume events occur, nor that toxic organophosphates are present. The remaining hurdle is to connect the hundreds of sick pilots and cabin crew with the events. Some, like Michaelis, say that is obvious.

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Source: Flight International