Development of assays for the detection of photomutagenicity of chemicals during exposure to UV light. II. Results of testing three sunscreen ingredients.

Three sunscreen ingredients, derivatives of benzylidene camphor, were tested for photomutagenic potential. These were benzenesulfonic acid, 4-[(4,7,7,-trimethyl-3-oxo-bicyclo [2.2.1] hept-2-ylidene) methyl] (Mexoryl SL), 4-(2-oxo 3-bornylidenemethyl) phenyl trimethylammonium methyl sulphate (Mexoryl SO) and 3,3'-(1,4-phenylenedimethylidyne) bis [7,7-dimethyl-2-oxo-bicyclo [2.2.1] heptane-1-methanesulfonic acid] (Mexoryl SX). Two complementary assay systems were used, one involving the induction of reverse mutations in Escherichia coli strain WP2, the other measuring the induction of chromosome damage in Chinese hamster ovary (CHO) cells. Irradiation with UVA and/or UVB was provided by an Osram Ultra-Vitalux sunlamp. None of the three sunscreens, tested either to the limit of solubility or toxicity, gave any indication of photomutagenicity in either assay, under conditions in which the positive control compound, 8-methoxypsoralen, was extremely photomutagenic. It is concluded that Mexoryls SL, SO and SX can be exposed to UV light without producing photomutagenicity measurable using a bacterial reverse mutation or a mammalian chromosome aberration assay.