UK aerotoxic inquiry may head down the wrong path

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The UK Department for Transport has been carrying out exploratory tests to decide the best methods for detecting chemicals that are present in cabin air contamination events, following many well-documented serious incidents in commercial air transport aircraft in the past 25 years.

A high proportion of the events were associated with the British Aerospace 146 series and Boeing 757s, and the DfT exploratory tests have been targeting these, but some events have been reported in all aircraft types pressurised using engine bleed air.

In 2000 an Australian Senate inquiry ruled that toxic fumes generated by organophosphates from heated engine oil additives had not only threatened safety, but had caused chronic sickness in flight crew and cabin crew. Possible effects on passengers have never been studied.

The Royal Australian air force, which had encountered similar problems with military aircraft such as the Lockheed C-130 Hercules and the General Dynamics F111, studied the problem and acknowledged its existence. The UK DfT, meanwhile, has acknowledged the need for a technical study and is defining the terms of reference for the tests, but has not been able to explain why it has begun the study now rather than immediately after the Australian Senate report, given that the aircraft most frequently cited is the 146 series, a British-certificated design.

It is becoming clear early in the DfT inquiry that it is being selective in sourcing the data on which it bases its terms of reference. It has refused to use a major reference document known as "The Aviation Contaminated Air Reference Manual" (ACARM) that has just been favourably reviewed by aviation medical specialist Dr Bhupi Singh, associate professor and head of research at the RAAF Institute of Aviation Medicine.

Delivering his verdict on the 815-page manual - the only single-source document that brings together referenced data on all known events, studies and inquiries on aero-toxicity - Singh says: "The events data pertains to a wide range of aircraft operators in many countries spread across the globe. All data is extensively researched and referenced, with its source clearly identified. In fact, one of the strengths of the manual is its extensive referencing."

Singh continues: "A notable and distressing element of the data is the widespread prevalence of denial of the existence of the problem, particularly among the aircraft operators and aviation regulators."

Meanwhile, Prof Clement Furlong, research professor of genetics and medicine at the University of Washington, Seattle, who presented a paper on "Organophosphates: the effect on pilots and passengers" at the Flight International Crew Management Conference in Brussels in December, revealed he is well down the research path to establishing conclusively the neurological effects that specific cocktails of organophosphates can have on the human brain.

In charge of the UK DfT investigation is an eminent psychologist, Prof Helen Muir, who has conducted world-renowned research on many aviation subjects, including human behaviour during aircraft emergency evacuation, but the appointment of a psychologist to head a task of this nature has been questioned by several interested bodies, including the Global Cabin Air Quality Executive (GCAQE), which represents pilots and other aviation workers whose health has suffered from toxic air on board aircraft. Capt Susan Michaelis, the GCAQE's chief researcher, is the author of the ACARM.

Other authorities, including the GCAQE, that have attempted to submit evidence to the DfT have also been rebuffed. One apparent reason for the selectiveness over sources is the recent report on cabin air by the UK Committee on Toxicity (COT), which alleges there is no proof that oil-contaminated air has been, or could be, the cause of chronic illness in flight and cabin crew. But the COT's findings were based on a study that also refused to accept for consideration data from the ACARM, and would not hear evidence from the GCAQE.

It has been established by a UK House of Lords inquiry that cabin air contaminants are caused by leaking engine oil seals releasing oil that undergoes thermal decomposition (pyrolysis) into a range of substances such as volatile organic compounds, low molecular weight organic acids, esters, ketones and tri-cresyl phosphate isomers (TCP), yet the COT has stated there is no proof that TCP has been present in any of the documented cases.

Michaelis says this is quite simply wrong, but she fears there is a danger that the DfT tests may not be specifically designed to detect TCP, which is reckoned by the GCAQE to be the critical component of the brain-affecting chemicals.

Aviation Contaminated Air Reference Manual