OPs Cause Bad Trips?

Do leaks of hydraulic fluids and jet engine lubricating oils cause potentially toxic fumes to be released into the cabins of commercial airliners? If so, do those fumes cause acute and chronic health problems such as headache, nausea, fatigue, memory loss, and neuromuscular damage in airline crew members and passengers? Those simple questions are at the heart of a brewing controversy.

Advocacy groups and trade unions representing pilots and flight attendants have collected hundreds of anecdotal reports from over the past 20 years that they claim show a long-term pattern of incidents involving smoke or foul-smelling fumes being released into airliner cabins, resulting in acute and chronic symptoms among the people exposed. The scenario that they and Some scientists who have examined the issue have set forth is that these fumes may contain organophosphates or carbon monoxide.

Organophosphates are present in some hydraulic fluids and engine oils. It is suspected that in many cases the fumes are caused by leaks of hydraulic fluid or jet engine oil from faulty lines or seals into super-heated engine parts. There, the fluids are vaporized into gases and pass into the passenger cabin air supply. Carbon monoxide is produced when oils are chemically altered through heating.

Many people who have gotten sick in these incidents report neurotoxic symptoms that appear to be consistent with organophosphate or carbon monoxide exposure. Several crew members claim to have become temporarily or permanently disabled as a direct result of their exposure to toxic fumes. In one noteworthy case, 26 flight attendants employed by Alaska Airlines sued that carrier, claiming that noxious fumes in aircraft cabins had made them sick. In settling the case in January 2001, the flight attendants signed a statement acknowledging that the company had not intentionally caused them harm. But related litigation continues against Boeing, the manufacturer of the airplanes in the Alaska Airlines case, and Honeywell, the maker of an engine component suspected to be central to the problem.

Christiaan van Netten, head of the Division of Occupational and Environmental Health at Canada's University of British Columbia, who is analyzing leakage incidence data, says leakage occurs in about 1 out of 1,000 flights and is usually traceable to equipment failure. He adds that incidence depends largely on the type of aircraft and the maintenance habits of the airline.

Experts largely agree there is a lack of well-collected, objective exposure and health effects data. Most of the existing data are anecdotal, with only a few laboratory analyses done on oil and fluid constituents and some medical reports from flight attendants and crew members. But the evidence compiled to date has been sufficient to generate several official inquiries into the issue of airliner cabin air quality.

The most comprehensive study so far, Air Safety and Cabin Air Quality in the BAe 146Aircraft, was completed in October 2000 by an Australian Senate committee. The BAe 146, manufactured by British Aerospace, has been the subject of many toxic fume complaints in Australia and elsewhere. Notably, the committee concluded that "it appears ... that contamination of cabin aircraft air on the BAe 146 aircraft has led to short-term and medium-term health problems for a number of BAe 146 flight crew," including vomiting, difficulty breathing, disorientation, and chemical sensitivities.

The Senate report recommends several actions, from improved maintenance of the aircraft and more stringent monitoring of air quality to further study of the issue in general find a review of the jet oil used in the BAe 146. That oil, Mobil Jet Oil II, contains the organophosphate tricresyl phosphate (TCP), which several witnesses in the Australian Senate hearing felt was the compound causing health problems among exposed crew members and passengers. Mobil officials testified, however, that "there is no record of a jet oil formulated with modern conventional TCP causing human toxicity."

The Science and Technology Committee of the British House of Lords responded less sympathetically to similar evidence of TCP-related adverse health effects in aircraft cabins. In its November 2000 Fifth Report, the House of Lords committee concluded that "the absence of confirmed cases of TOCP [a highly toxic isomer of TCP] poisoning from cabin air and the very low levels of TOCP that would be found in even the highly unlikely worst case of contamination from oil leaking into the air supply lead us to conclude that the concerns about significant risk to the health of airline passengers and crews are not substantiated."

Now the U.S. Federal Aviation Administration is sponsoring a congressionally mandated review that is being conducted by a National Academy of Sciences committee. The review is assessing air quality conditions, associated health effects, and factors contributing to potentially toxic exposures in passenger cabins of commercial aircraft, with particular attention to be paid to the toxicologic effects of contaminants of concern, including those in engine oils and hydraulic fluids. The committee plans to release a final report in the autumn of 2001.