Inappropriate Use of Risk Assessment in Addressing Health Hazards Posed by Civil Aircraft Cabin Air

Abstract

Over decades, the airline industry has published considerable documentation on the potential for inhalation exposure to organophosphates and other toxins sourced to engine oil fumes supplied by “bleed air” systems, which are used on most commercial and military aircraft. Case studies on the subsequent development of neurological and other symptoms reported by crewmembers have also been widely documented. However, airline industry reviews tend to define toxicity of engine oil fumes according to a single toxicological endpoint - Organo Phosphate Induced Delayed Neuropathy (OPIDN) – which is acknowledged to be the result of a very high dose of exposure to a specific chemical, Tri-Ortho Cresyl Phosphate (TOCP). Industry reviews typically argue that the low levels of TOCP in aviation engine oils justifies the safety of continuing to use unfiltered engine bleed air to ventilate civil and military aircraft cabins. In fact, this approach ignores the routine presence and toxicity of a complex mixture of OPs in oil fumes supplied by engine bleed air systems and ignores the type of neurological symptoms that crews report (i.e., not OPIDN). The industry approach also ignores the scientific literature on repeated low-dose exposure to OPs over extended periods (particularly relevant for airline crewmembers) and the variable susceptibility of individuals to toxicological damage. This paper reviews the above-mentioned studies and presents the scientific literature that should be considered to make a realistic risk assessment of the hazards of aircraft engine bleed air.