Synthetic ultraviolet light filtering chemical contamination of coastal waters of Virgin Islands national park, St. John, U.S. Virgin Islands

• Coastal waters of Virgin Islands National Park (VINP) were sampled for the presence of synthetic UV screen chemicals.
• 4-methylbenzylidene camphor, benzophenone-3, octinoxate, homosalate, and octocrylene were detected.
• The highest detected concentrations were for BP-3 (6,073 ng/L) followed by homosalate and octinoxate.
• Concentrations declined with distance from the beach at Trunk Bay, the location of greatest visitation in VINP.

Contamination of surface waters by synthetic ultraviolet light (UV) filtering chemicals is a concern for the Virgin Islands National Park (VINP). Discrete water samples were collected from VINP bays to determine UV filter chemical presence in the coastal waters. Spatial distribution and the potential for partitioning between subsurface waters and the sea surface microlayer (SML) were also examined. The UV filter chemicals 4-methylbenzylidene camphor, benzophenone-3, octinoxate, homosalate, and octocrylene were detected at concentrations up to 6073 ng/L (benzophenone-3). Concentrations for benzophenone-3 and homosalate declined exponentially (r2 = 0.86 to 0.98) with distance from the beach. Limited data indicate that some UV filter chemicals may partition to the SML relative to the subsurface waters. Contamination of VINP coastal waters by UV filter chemicals may be a significant issue, but an improved understanding of the temporal and spatial variability of their concentrations would be necessary to better understand the risk they present.