Cosmetic UV filters used in sunscreens and their impact on corals put into perspective

Abstract Coral reefs are declining worldwide due to various global and regional factors, with climate change and the associated warming of the oceans being one of the primary drivers. Recreational beach activities lead to the direct emission of sunscreen products and their UV filters into coastal marine environments and thus may impact coral health. However, although sunscreen formulations may be optimized in some regions by using non-hazardous UV filters, in many countries with coral reef abundance, additional emissions may occur due to untreated and insufficiently treated wastewater. For lipophilic ultraviolet absorbing (UV) filters, however, adequate treatment of domestic wastewater would significantly (up to > 90%) reduce such indirect emissions. Furthermore, such measures would also help to improve both river and coastal water quality, as domestic wastewater typically contains many more substances resulting from other uses such as personal and homecare, pharmaceuticals, disinfectants, and biocides. As these provisions are both cost and time consuming, prioritization of improvement needs may be supported by standardized and validated test methods (preferably under ISO) that allow for a toxicity assessment of effluent streams on corals. Furthermore, these methods may also be used to identify substances considered critical for coral health. The ban of certain cosmetic UV filters in some regions may not be considered a suitable solution to maintain coral reefs. Thus, from a more holistic approach, improving wastewater management would contribute to the maintenance of coral reefs on a local scale, especially in areas (e.g., islands originating from volcanic activities) that are less affected by rising sea surface water temperatures.