Ethylhexyl triazone sunscreen and its disinfection byproducts obtained after chlorine treatment: Ecofriendliness or ecotoxicity?

In recent years, there has been a growing demand for high-quality sunscreens that combine high efficacy with ecological characteristics. This trend has led to an increased use of triazine compounds, which represent an emerging class of UV filters. While it is well-established that sunscreens can have significant environmental impacts, there is limited data on the degradation of triazine UV filters, despite available information on their environmental persistence, particularly in relation to disinfection processes. This study investigates the chemical fate of ethylhexyl triazone (EHT) under chlorination conditions, typical of swimming pools. Twelve disinfection byproducts (DBPs) were isolated and fully identified using nuclear magnetic resonance and mass spectrometry, with three of these byproducts being identified for the first time. DBP1-DBP12 were isolated at relative percentages of 1.26, 9.68, 1.05, 0.42, 0.84, 3.37, 3.58, 1.89, 0.84, 1.47, 0.42, and 0.63. Additionally, a mechanism for their formation was proposed. The ecotoxicological assessment of EHT and of byproducts (DBP1-DBP4) was conducted using acute, sub-chronic or chronic toxicity tests in producers and primary consumers of the freshwater trophic chain. The organisms included the alga Raphidocelis subcapitata, the rotifer Brachionus calyciflorus, the crustacean anostracan Thamnocephalus platyurus and the benthic ostracod Heterocypris incongruens. EHT caused a lethal median concentration in rotifers, with values in the range of tens of mg/L. EHT, DBP1, and DBP4 exhibited sub-chronic effects in ostracods at concentrations in the μg/L range, with EC50s of 210, 9, 20 μg/L, respectively. Rotifers were slightly affected by DBP3 with a chronic EC50 of 200 μg/L. Algae were not affected by either EHT or byproducts.