Toxicity assessment of binary mixtures of BP3 with 4-MBC (UV-filters), and BP3 with DEET (insect repellent) using the aquatic midge Chironomus riparius

Personal care products have various organic ultraviolet filters (UV filters) in their composition to increase protection against ultraviolet radiation. Some of these products also contain insect repellents in their formulations. Consequently, these compounds reach freshwater ecosystems, exposing aquatic organisms to a cocktail of anthropogenic contaminants. In this study, the joint effects of two most frequently detected UV filters (Benzophenone - 3 (BP3) and Enzacamene (4-MBC)) and joint effects of BP3 combined with an insect repellent (N, N diethyl-3-methylbenzamide - DEET) were evaluated using life-history traits of the aquatic midge Chironomus riparius such as emergence rate, time to emergence and imagoes body weight. The results showed synergistic effects between BP3 and 4-MBC for C. riparius emergence rate. Regarding the effects of BP3 and DEET mixture, our analysis suggests synergism in the case of males but antagonism in the case of females' time to emergence. Our results imply that the effects of UV filters present in sediments within chemical mixtures are complex and that the evaluation of effects using different life-history traits can yield different patterns of responses. This study demonstrates the importance of assessing the combined effects of pollutants used/found concomitantly in aquatic systems for a more accurate risk assessment, as individual chemical testing can underestimate the toxicity of organic UV filters.

Automated summary

Personal care products containing organic ultraviolet filters (UV filters) and insect repellents can introduce anthropogenic contaminants into freshwater ecosystems, impacting aquatic organisms. This study evaluated the combined effects of two commonly detected UV filters (Benzophenone-3 (BP3) and Enzacamene (4-MBC)) and BP3 combined with an insect repellent (N,N-diethyl-3-methylbenzamide - DEET) on the life-history traits of Chironomus riparius. The results showed synergistic effects between BP3 and 4-MBC on emergence rate, whereas the effects of BP3 and DEET mixture differed for males and females. The study highlights the complexity of chemical mixtures in sediments and the importance of assessing their combined effects for accurate risk assessment.