Synopsis

Phototoxicity or photoirritation, has historically been evaluated in mice or pigs by various methods as a safety test prior to initial exposure of humans. These methods have been expensive. We have modified an assay for routine valuation of fragrance chemicals for phototoxic potential prior to HUMAN TESTING. Our method uses ultraviolet (UVA) irradiation during diffusion of test chemicals from a paper disc placed upon agar freshly seeded with Fleischman's Baker's Yeast. A concurrent positive control, 8-METHOXYPSORALEN is tested at 10-4%. The test for each chemicall: is contained within a four-compartment plasticunit. Light-specific zones ofinhibited yeast growth 'r•flect phototoxic events. Duplicate units are run in the absence of ultraviolet light to account for any direct, UV-independent anti-fungal activity. Correlations are made with UV ABSORPTION data. The test is inexpensive, simple to conduct and provides results within 72 hours. Correlations with positive human phototoxicity results have been excellent. The test provides a tool to easily pre-screen for phototoxic changes related to structural modifications of useful chemicals. It is used primarily to set safe initial dose levels for human panelists inthe hazard assessment program. i'