The formation of phosgene by the action of hot surfaces and its absence when tobacco is smoked in atmospheres containing chlorinated hydrocarbon vapours.

When trichloroethylene or certain other solvent vapours are heated to a temperature of 4000 C. or more, or when the liquids decompose by exposure to light on standing in air, phosgene is produced. It is generally believed or assumed from this that when cigarettes are smoked in atmospheres contaminated with the solvent vapours phosgene is also produced and inhaled. However, nowhere in the literature is experimental evidence given of phosgene being positively identified in the inhaled gases from a cigarette smoked in these contaminated atmospheres although the danger has been pointed out by several writers, including McNally (1937), Oettingen (1937), and Converse (1938). A secondary danger may exist from the glowing cigarette tip in the atmosphere around the cigarette. Elkins and Levine (1939) carried out a comprehensive series of tests in which the effluent from cigarettes smoked in atmospheres containing a number of halogen-containing hydrocarbon vapours was examined. They did not test the inhaled gases specifically for phosgene, but, on the basis of the halide content of the exit gases, calculated that even if all the halogen found was so present it would not constitute a health hazard. The tolerance limit for continual exposure to phosgene in the atmosphere is stated by Patty (1949) to be 1-0 part per million by volume, a concentration of 2 parts per million being dangerous for prolonged exposure. In view of the extremely toxic nature of phosgene, therefore, it is essential that smoking in the presence of these solvents be forbidden unless it can be demonstrated by a test of adequate sensitivity that phosgene is not present in the exhaled tobacco smoke or formed in the surrounding atmosphere. The Detection of Phosgene