Ultraviolet (UV) filter chemicals are the active ingredients used in sunscreens, lotions, cosmetics and other personal care products to protection the skin from UV light. One commonly used UV filter chemical is octyldimethyl para-aminobenzoic acid, better known by its commercial name as Padimate O. UV filter chemicals enter the aquatic environment via direct (e.g., swimming) and indirect (e.g., wastewater treatment plant effluent) routes; though they are designed to be photostable, several are known to degrade upon exposure to UV light, which has implications for their effectiveness in sunscreen products and their fate in the environment. In this study, the aqueous photolysis of Padimate O was investigated under natural and simulated sunlight to determine the kinetics and mechanism of direct photolysis and the importance of indirect photolysis. The quantum yield for the direct photolysis of Padimate O is 0.0016, and its half-life due to direct photolysis is approximately four hours. Results from photolyses in the presence of varying concentrations of several humic and fulvic acids indicate that indirect photolysis is much less important than direct photolysis for Padimate O. In addition, the direct photolysis kinetics appear to be independent of pH over an environmentally relevant pH range. Liquid chromatography � mass spectrometry was used to investigate the products of direct photolysis, including two demethylated products and one methylated product. Results also indicate the formation of dimers of Padimate O, which have not been previously reported in the scientific literature. Current studies are focused on isolating the direct photolysis products using preparatory-scale chromatography techniques in order to assess their cellular toxicity. The data obtained in this study may be used to assess the fate of Padimate O in the aquatic environment and to make informed decisions about its use in consumer products.

Aqueous photolysis of the common ultraviolet filter chemical octyldimethyl para-aminobenzoic acid (Padimate O)

247th National Meeting (2014)

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