Potentiation of lethal and sub-lethal effects of benzophenone and oxybenzone by UV light in zebrafish embryos

Benzophenones are widely used as organic UV filters in many personal care products, especially sunscreen, to protect humans from UV radiation. The increasing use of benzophenone class UV filters has raised concerns about the potential effects on the aquatic environment. These organic UV filters are designed to absorb UV light. However, to date, studies have not considered the potential of UV light to potentiate the toxicity of benzophenones in aquatic organisms. In this study using zebrafish embryos, we assessed the median lethal concentration (LC₅₀) and sub-lethal effects of benzophenone and oxybenzone either under natural levels of UV light or under laboratory light conditions. The LC₅₀ value in zebrafish embryos under both light conditions of oxybenzone was lower when compared to benzophenone. Interestingly, UV light significantly decreased the LC₅₀ values (increased toxicity) of both benzophenone and oxybenzone. The presence of UV light induced a significant increase in hydroxyl radical formation and this was reflected in both increased SOD activity and lipid peroxidation in oxybenzone treated groups. Exposure to either benzophenone or oxybenzone also delayed hatching between 60 and 96 hpf when comparing to the control group while UV exposure further delayed hatching only in oxybenzone-exposed embryos. The results demonstrate the importance of involving UV light in toxicity testing for UV filters and provide much-need information on the UV-induced toxicity of benzophenone and oxybenzone under ecologically realistic conditions.