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Table 5 The Bradford Hill approach applied to Aerotoxic Syndrome (2017)

From: Health consequences of exposure to aircraft contaminated air and fume events: a narrative review and medical protocol for the investigation of exposed aircrew and passengers

Strength of association: Case studies and clinical data indicate clear health impacts in significant proportions of exposed groups.

Consistency: Clinical data consistent with known toxic effects of organophosphates; and across varying aircraft types / countries.

Specificity: Aerotoxic Syndrome is a syndrome (as is Acquired Immune Deficiency Syndrome; Multiple Chemical Sensitivity; Occupational Asthma; Gulf War Syndrome and Asperger’s Syndrome) and with common neurological/respiratory symptoms linked to oil leakage/pyrolysis products exposure in cabin air.

Temporality: Aerotoxic Syndrome was never reported prior to the introduction of engine bleed air pressurization systems and cabin air contamination precedes linked health effects.

Biological gradient: High contaminant exposure often causes greater health effects; but low dose effects also apparent, suggesting non-linearity.

Plausibility: The known effects of organophosphates and other cabin air contaminants support a causal link.

Coherence: Animal and human data support a causal link.

Experiment: Some health effects are reversible after exposure cessation, especially for acute exposures.

Analogy: Polychlorinated biphenyls; hot rubber fumes; welding fumes; traffic fumes, occupational asthma, leaded petrol, methyl mercury, organophosphate pesticides and tobacco smoke have relevant features.

  1. Data source: [207]