The absorption of tri-ortho-cresyl phosphate through the skin of hens and its neurotoxic effects.

General and neurotoxic effects of ingested triortho-cresyl phosphate *(TOCP) in man and animals have been described in detail for the last 20 years. We refer here only briefly to the clinical literature where TOCP was implicated, such as Jamaica ginger paralysis in America (Aring, Bean, Roseman, Rosenbaum, and Spies, 1941; Aring, 1942); the massive intoxications by engine oil at the beginning of the Second World War in Germany (Creutzfeldt and Orzechowski, 1941-43), in Switzerland (Moeschlin, 1952), and recently in Morocco (Smith and Spalding, 1959). Experiments on animals to study the dosage and the histology have been carried out by Barnes and Denz (1953), Cavanagh (1954), Hierholzer, Noetzel, and Schmidt (1957), Glees (1957), Silver (1959), Bondy, Field, Worden, and Hughes (1960), and Glees and White (1960). While these studies have clarified the amounts of TOCP necessary for producing toxic effects, little attention has been paid to the possibility that TOCP might be absorbed by the skin so readily that it would also damage the central nervous system. The likelihood of TOCP coming in contact with the skin in industrial workers is great as it is contained in small amounts in some plasticisers, lubricants, and petrol additives, as well as in certain lacquers. That skin absorption is possible was demonstrated by Hodge and Sterner (1943) using radio-active TOCP compounds. We decided therefore to study in a systematic way the amount of TOCP to be painted on the skin of hens necessary to cause symptoms, and to investigate neurohistologically the degree of nerve fibre degeneration.