Cognitive function following exposure to contaminated air on commercial aircraft: A case series of 27 pilots seen for clinical purposes

Background. Cabin air on commercial aircraft is sometimes contaminated with hydraulic fluids, synthetic jet engine oils and combusted or pyrolized materials. The incidence of contaminated air events is hard to quantify as commercial aircraft do not have air quality monitoring systems on board. In the UK, around 350 aircrew have advised their union that they may be suffering physical and psychological ill health following exposure to contaminated air. Design. This paper presents a case series of 27 pilots referred for psychological assessment. The general aim of the assessment was to determine whether pilots show evidence of cognitive impairment and whether this relates to exposure history. Materials and method. All pilots underwent neuropsychological and adult mental health assessment, undertaken by 12 examiners, instructed to search for alternative explanations other than exposure to toxic fumes for any symptoms reported. Results. Pilots reported alarming cognitive failures at work such as being unable to retain or confusing numerical information from Air Traffic Control. Nine pilots were excluded from further analysis because they had a medical or psychiatric condition which might otherwise explain these difficulties. In the remaining 18 pilots, language, perceptual skills and general intellectual ability were preserved, but performance on tests of psychomotor speed, attention and executive functioning was below expected levels. Conclusions. The cognitive deficits identified in this cohort of pilots cannot be attributed to factors such as mood disorder or malingering. However, the evidence available in this study does not enable firm conclusions to be drawn regarding a causal link with contaminated air; the cohort of pilots was self-selected and only crude indices of exposure were available. Further research is warranted given the scientific uncertainty regarding the health effects of inhalation of heated or pyrolized engine oil.