Olefinic hydrocarbons: a first risk estimate for ethene.

The exhalation of ethene oxide by rats exposed to ethene now allows a first estimate of the genotoxic risk of ethene on a pharmacokinetic basis. The distribution (Keq, Kst) of ethene oxide under conditions of inhalation of ethene oxide, or high levels of ethene and consideration of the saturation behaviour of metabolism of ethene lead to the conclusion that inhalation exposure of rats to 1000 ppm ethene or more would theoretically correspond to about 7.5 ppm ethene oxide exposure. Available carcinogenicity data for inhaled ethene oxide were utilized into a comparison of the genotoxic risks of low levels of ethene oxide and ethene. It has been shown that consideration of ethene as a "simple asphyxiant" is inappropriate. The new intended TLV of 1 ppm for ethene oxide would be consistent with a TLV of 100 ppm for ethene.