Acute toxicity of novel triazine-based UV filters towards Chlorella vulgaris and Daphnia magna: Single and mixture effect

The increasing utilization of novel triazine-based UV filters (UVFs) has drawn significant attention regarding their potential toxicity to aquatic organisms. However, there is limited toxicity data for these emerging UVFs. Herein, we evaluated acute toxicities of triazine-based UVFs including bis-ethylhexyloxyphenol methoxyphenol triazine (BEMT), diethylhexyl butamido triazone (DBT), and ethylhexyl triazone (EHT), towards Chlorella vulgaris and Daphnia magna. For comparison, the acute toxicities of three commonly used non-triazine-based UVFs, namely diethylamino hydroxybenzoyl hexyl benzoate (DHHB), avobenzone (AVB), and octocrylene (OCR) were also assessed. Simultaneously, we investigated the acute mixture toxicity of these compounds on Daphnia. Under single-compound exposure (≤15 mg/L), BEMT, DBT, and EHT demonstrated less than 10 % growth inhibition in Chlorella. In contrast, DHHB, AVB, and OCR exhibited concentration-dependent inhibition. Based on 48-hours EC₅₀ values for Daphnia, the triazine-based UVFs were markedly less toxic than the non-triazine counterparts. Mixture exposure experiments revealed an antagonistic effect for combinations such as BEMT+EHT, BEMT+EHT+DHHB, and DHHB+EHT, whereas the mixture AVB + OCR+ BEMT exhibited primarily synergistic effects, likely attributed to distinct modes of action among its components. This study suggests that triazine-based UVFs exhibit lower acute toxicity under the conditions tested to Chlorella growth inhibition and Daphnia immobilization than the conventional non-triazine UVFs tested, providing essential data for the environmental risk assessment of these emerging contaminants.