The ortho-isomer is rarely used on its own outside of laboratory studies that require isomeric purity, due to its extremely toxic nature, and is generally excluded from commercial products where TCP is involved.

[3] However, researchers at the University of Washington found that non-ortho TCP isomers present in synthetic jet engine oils do inhibit certain enzymes.

The earliest known mass poisoning event by TOCP occurred in 1899 when six French hospital patients were given a phosphocresote cough mixture containing the organophosphate compound.

In medical journals it was described to have produced an organophosphate-induced delayed neuropathy (OPIDN) neurodegenerative syndrome, "characterized by distal axonal lesions, ataxia, and neuronal degeneration in the spinal cord and peripheral nervous systems.

[13] Apiol was subsequently criticized by doctors, journalists, and activists until it was discontinued, citing that the dangers were too great and the number of poisonings was likely higher than accounted for.

[14] Other mass poisonings[8] include: TCP is used as an additive in turbine engine oil and can potentially contaminate an airliner cabin via a bleed air "fume event".

Aerotoxic syndrome is the name given to the alleged ill effects (with symptoms including memory loss, depression and schizophrenia) caused by exposure to engine chemicals.

In tandem, TOCP exerts physical damage by causing axonal destruction and myelin disintegration within specialized cells that transmit nerve impulses (neurons).

The dangers in metabolizing TOCP to CBDP occur when its potential to bind to AChE become imminent, for inactivation of the enzyme in nerve synapses can be lethal.

"[19] Upon inactivation, acetylcholine can no longer be broken down in the body and results in uncontrollable muscle spasms, paralyzed breathing (bradycardia), convulsions, and/or death.

[21] In humans, the first symptoms are weakness/paralysis of the hands and feet on both sides of the body due to damage to the peripheral nervous system (polyneuropathy) and a sensation of pins-and-needles (paresthesia).