In flight, every crew member and passenger relies on an air supply. The assumption, of course, is that this air is filtered if not fresh. Perhaps you have sensed (and promptly dismissed) that there may be quality control issues around cabin air. The problem goes further than that, however, and astoundingly, this is not by accident but by design.
As a result of poor design, every breath that the crew and passengers take today, consists of a 50/50 mix of recirculated cabin air and bleed air, the latter of which can contains a wide range of synthetic chemicals, such as tricresyl phosphate (TCP or TOCP), an organophosphate which is highly neurotoxic to humans. In fact, the World Health Organisation stated in 1990 that “Because of considerable variation among individuals in sensitivity to TOCP, it is not possible to establish a safe level of exposure” and “TOCP are therefore considered major hazards to human health.”
…with the exception of single aircraft — the new Boeing 787, where cabin air is taken directly from the atmosphere with electrically powered compressors — all flights today involve a high risk of exposure to these neurotoxic chemicals. When you consider there are about 100,000 flights a day (only 5% of which occur on “safe” Boeing 787’s, with at least 1 in 100 flights experiencing a major ‘fume event,’ this amounts to the health endangerment of millions of daily passengers.