Genetic toxicity of styrene and some of its derivatives.

Styrene, an important plastic monomer, is mutagenic after metabolic activation in several test systems. Probably because of an unfavorable activation : inactivation ratio, some mutagenicity assays have not, however, found styrene mutagenic. Styrene is converted by microsomal monooxygenases in vivo to styrene-7,8-oxide, which is a well-known mutagen. Arene oxides have also been proposed as the reactive metabolites of styrene, but the significance of these compounds is not yet fully understood. Only few derivatives of styrene have been tested for mutagenicity. The results are characterized by difficulties in metabolic activation. Many styrene-7,8-oxide analogues substituted at the phenyl ring are electrophilic reactants and mutagenic in vitro. Human whole-blood lymphocyte cultures have a peculiar feature, ie, styrene and many of its analogues substituted at the ring or vinyl chain induce sister chromatid exchanges in the cultured cells without exogenous metabolizing systems. This activation is brought about by erythrocytes present in the cultures and probably results from the conversion of styrenes to styrene-7,8-oxides.