Development of a novel rinse-off method for improved sunscreen exposure assessment

Recent legislative measures restricting the sale of sunscreens containing certain ultraviolet light filtering ingredients (UVFs) have been based on a perception of risk to aquatic life despite the lack of a robust data set to support these decisions. Concerns were focused on the potential for recreational swimmers' and divers' sunscreen use to result in exposures to coral already stressed due to climate change, disease, and other local conditions. In published environmental risk assessments for UVFs, exposure estimates were based on episodic environmental monitoring or estimates of typical sunscreen use, arbitrarily assuming the portion rinsed off from skin in seawater. To improve the accuracy of exposure estimates and thereby develop more robust risk assessments, we measured the amount of the UVFs, avobenzone, homosalate, octisalate, octocrylene, and oxybenzone released to seawater from four sunscreen products (two lotions, one spray, one stick) in a novel porcine skin model of typical human sunscreen use. Sunscreen was applied to porcine skin, allowed to briefly dry, then exposed to four rinse cycles in artificial seawater. The mass of each UVF in seawater, partitioned from seawater onto glassware, and extractable from skin after rinsing were determined. The proportion rinsed from skin varied by UVF, by formula type, and by application rate. Less than 1.4% of applied octisalate, homosalate, and octocrylene was detected in seawater samples (independent of formula) increasing to an average of 4% and 8% for avobenzone in stick and lotion forms, and to 24% for oxybenzone in lotions. The initial data show substantial differences in rinse‐off among formulation types and sunscreen application rates, and stress the importance of using UVF‐specific rinse‐off values rather than a single value for all UVFs. This new method provides a tool for more robust exposure estimates, with initial data supporting lower rinse‐off values than adopted in published risk assessments. Integr Environ Assess Manag 2021;17:961–966. © 2021 Johnson & Johnson Consumer Companies Inc. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).
KEY POINTS Regulatory decisions on sunscreen use have been made on the basis of potential risk to coral, but published risk assessments for sunscreens' ultraviolet light filter (UVF) ingredients lack empirical data to establish their rinse‐off rate from swimmers' skin into seawater.A method was developed to reproducibly simulate rinse‐off of UVFs in sunscreen from skin into seawater, and the method was tested for stick, lotion, and spray formula types.Rinse‐off of the five UVFs in these formulas—octocrylene, octisalate, homosalate, avobenzone, and oxybenzone—varied substantially and depended on the sunscreen formula type and application rate.The initial results suggest that published risk assessments adopted artificially high rinse‐off rates, and future assessments should account for differences among UVFs and for the sunscreen formula types used.