Screening-level exposure models to evaluate the direct release of cosmetic ingredients: development and application to ultraviolet-light filters used in suncare products

Concerns regarding the environmental risks of UV-filters used in suncare products have grown in recent years. Much of this concern has been driven by their use in products by consumers engaged in outdoor recreational activities, such as swimming, which can facilitate their direct emissions into aquatic systems. Uncertainties in estimating the amount of a UV-filter that might be directly emitted to water, however, represent a continuing challenge, and include the need to quantify the number of users of suncare products, the skin area covered, the concentration of the UV-filter in the product and the extent to which the UV-filter is 'washed-off'. This study aims to address this gap, which includes the development and application of screening-level exposure Models to Evaluate the direct Release of Cosmetic Ingredients (MERCI). The tier 1 and 2 MERCI models-SUNscreen and multi-SUNscreen-are described, with application to octocrylene, a well-studied UV-filter used in suncare products. Model results suggest that both tools provide reasonable estimates of environmental exposure. Specifically, the tier 1 SUNscreen model, estimates an environmental concentration of 422 ng·L-1 in freshwater and range from 191-428 ng·L-1 in marine water capturing differences between low-moderate tidal dilution rates, whereas sediment concentrations are estimated to be 206 ng·g-1 dw (freshwater) and 94-210 ng·g-1 dw (marine). The tier 2 multi-SUNscreen model, on the other hand, estimates freshwater concentrations of 81 ng·L-1 in water and 0.5 ng·g-1 dw in sediment, results that are observed to be within an order of magnitude of monitoring data. Overall, both models support a conservative, screening-level approach for estimating environmental exposure to UV-filters, and thus represent tools that can be readily utilized to support both risk assessment and research prioritization.