Photolysis of Organic Ultraviolet Filter Chemicals

Chemicals are a very big part of our lives and have both harmful and beneficial aspects, but would anyone think that everyday products such as sunscreen or cosmetics would have harmful chemicals in them? Organic ultraviolet filter chemicals (UVFCs) are the active ingredients in most sunscreen products and in some cosmetics. These chemicals are used to protect the skin from the damaging effects of sunlight exposure. However, when these products are used, the chemicals end up in the environment. Traces of organic UVFCs have been found in our water, sewage, fish and even humans. When the UVFCs are exposed to sunlight many degrade, and little is known about the environmental fate and potential toxicity of the resulting photoproducts. One commonly used UVFC we are interested in is octyldimethyl para-aminobenzoic acid (OD-PABA), which readily degrades in sunlight. The most common products that contain OD-PABA are lipsticks and lip balms. Some work has been done in the MacManus-Spencer lab on the photochemical degradation of OD-PABA, and the structures of three photoproducts have been proposed. The overall goal of this project is to study the mechanism of OD-PABA photolysis, characterize photoproducts and test their toxicity. Direct photolyses of OD-PABA in pure water have been conducted. To simulate “real-world” conditions in a controlled way, indirect photolyses in water with well characterized dissolved organic matter (DOM) were also conducted. DOM absorbs sunlight and transfers energy to OD-PABA or to dissolved oxygen, which may enhance the degradation of OD-PABA.