The National Academies of Sciences, Engineering, and Medicine (NASEM) released on August 9, 2022, a report entitled Review of Fate, Exposure, and Effects of Sunscreens in Aquatic Environments and Implications for Sunscreen Usage and Human Health. NASEM was tasked by Congress and funded by the U.S. Environmental Protection Agency (EPA) to undertake a consensus study of the potential risk of ultraviolet (UV) filters on already threatened aquatic environments and the potential consequence to human health should sunscreen usage or composition be modified. NASEM’s report reviews the state of science on the sources and inputs, fate, exposure, and effects of UV filters in aquatic environments, and the availability and applicability of data for conducting ecological risk assessments (ERA). It also reviews the epidemiological and clinical literature on the efficacy of sunscreen in preventing UV damage to human skin, the state of knowledge on potential human behavior changes, and the resulting health impacts related to skin cancer prevention from changes in sunscreen usage (e.g., reducing sunscreen use or switching to sunscreens with different active ingredients).
NASEM notes that the scope of the study is limited to the United States. According to the report, there are currently 16 UV filters allowed by the U.S. Food and Drug Administration (FDA) for use in any sunscreen sold in the United States, plus an additional proprietary UV filter, ecamsule, approved for use in limited products. While UV filters are used in a broad range of products, NASEM’s scope was to focus on their use in sunscreens. The 16 UV filters include two inorganic UV filters, titanium dioxide and zinc oxide. The summary of the attributes of UV filters relevant for assessment of environmental risk includes the following information for titanium oxide and zinc oxide:
- Titanium Dioxide: This is a metal oxide solid and as such will have different characteristics than organic compounds in that it exists in several particulate sizes and crystalline forms that impact its behavior and effects on organisms. Occurs in many consumer products and foods in both the macro and nano forms for applications other than as a UV filter. Effectively removed during wastewater treatment and occurs in low concentrations (< 10 [micrograms per liter (μg/L)]) in wastewater treatment plants [(WWTP)] effluent, no environmental degradation but aggregation with particles in surface waters, can exceed 1 μg/L in surface waters with higher concentrations noted in rivers and beach areas, potential for bioaccumulation but limited data on tissue levels, aggregates will deposit in sediments, effects on apical endpoints are greater than 1,000 μg/L in acute laboratory toxicity tests for the nano form and ten-fold or more higher for the macro form and less than 1,000 μg/L for chronic assays. However, in select studies in the presence of UV, some data on acute and chronic effects are available and indicate toxicity < 100 μg/L. Data are available for other biological responses.
- Zinc Oxide: This is a metal oxide solid placed in sunscreen in macro and nano particulate forms and as such will have characteristics different from organic compounds. Effectively removed by and low potential to be present in WWTP effluent, no environmental degradation but aggregation and dissolution of particles into the ionic form of zinc in the environment, can exceed 1 μg/L in surface waters with higher elevations noted in rivers and beach areas, potential for bioaccumulation supported by tissue studies, aggregates will deposit in sediments, effects on apical endpoints exhibit a wide range including effects at concentrations < 1,000 μg/L can be due to particulate or dissolution of the particulate internal or external to the organism, some data on chronic effects are available, data are available for modes of action and other biological responses.