Introduction and Context

Sunscreens and a variety of other products contain chemical ultraviolet (UV) filters that absorb or block the sun’s radiation and thereby help mitigate harms to human skin from the sun. These UV filters and the chemicals with which they are mixed can enter bodies of water directly, such as when people swim after applying sunscreen, or indirectly, such as through wastewater effluent carrying compounds that are rinsed off when bathing or showering. The 17 UV filters currently in use in the United States exhibit a wide range of properties in terms of biodegradability and toxicity, raising concerns about the potential for harmful impacts on the environment and in particular, on aquatic and marine organisms.

The 2022 National Academies of Sciences, Engineering, and Medicine (NASEM) report Review of Fate, Exposure, and Effects of Sunscreens in Aquatic Environments and Implications for Sunscreen Usage and Human Health¹ (referred to as “2022 report” throughout these proceedings) called on the U.S. Environmental Protection Agency (EPA) to conduct an ecological risk assessment of UV filters to characterize the possible risks to aquatic ecosystems and the species that live in them. However, the 2022 report also identified a number of knowledge gaps and research barriers that may limit understanding of those ecological risks.

To share progress and identify opportunities to further address gaps and barriers, NASEM hosted a workshop in Washington, D.C., on January 23–24, 2023, entitled Workshop to Advance Research on Understanding Environmental Effects of UV Filters in Sunscreens. The workshop brought members of government, academia, and industry together in person and virtually to discuss the knowledge gaps identified in the 2022 consensus study, consider research needs specific to the analytical challenges of working with UV filters, understand the environmental effects on aquatic ecosystems and nonstandard organisms, and share possible approaches to standardize toxicity testing.

Through a series of prepared talks, panel discussions, and structured breakout discussions, participants examined the 2022 report and its management context; explored data needs and analytical challenges relevant to the development of accurate toxicity metrics for UV filters; and suggested opportunities to improve and standardize toxicity testing for these chemicals.

These proceedings has been prepared by the workshop rapporteur as a factual summary of what occurred at the workshop. The planning committee’s role was limited to planning and convening the workshop. The views contained in the proceedings are those of individual workshop participants and do not necessarily represent the views of all workshop participants, the planning committee, or the National Academies of Sciences, Engineering, and Medicine.

WORKSHOP CONTEXT

Charles Menzie (Exponent, Inc.), chair of the committee that produced Review of Fate, Exposure, and Effects of Sunscreens in Aquatic Environments and Implications for Sunscreen Usage and Human Health, set the stage for the workshop with an overview of the 2022 report’s key findings and recommendations. Overall, Menzie stressed the committee’s finding that further research is needed to better understand the environmental fate of UV filters, reduce uncertainty

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¹ National Academies of Sciences, Engineering, and Medicine. (2022). Review of Fate, Exposure, and Effects of Sunscreens in Aquatic Environments and Implications for Sunscreen Usage and Human Health. Washington, DC: The National Academies Press. https://doi.org/10.17226/26381.

about their potential environmental effects, and enable the higher-tier ecological risk assessments (ERAs) necessary to protect the environments and organisms that interact with them.

The study included a rigorous review of the available data on the processes that influence the fate of UV filters in the environment; measurements in water, soil, and organisms; and environmental effects of the 17 UV filters currently marketed in the United States.² The 2022 report emphasized that there is significant variation among these UV filters and, in general, a dearth of knowledge regarding their properties, fate, and impacts. Laboratory studies have found that most UV filters are not biodegradable (with the caveat that studies done in natural water systems may have different results), and high-quality tests show a low-to-moderate potential for bioaccumulation of seven UV filters in aquatic life.³ However, the wide range of physical and chemical reactions that occur when UV filters enter water, from partitioning to photoreactions to dissolving to settling into sediments, makes toxicity testing and environmental monitoring very challenging.⁴ In addition, most of what is known about physico-chemical parameters has been learned from pure water experiments, laboratory conditions, or modeling simulations, and field studies of concentration levels typically lack knowledge of initial exposure in water or sediment. The question of how to perform chemical analyses of UV filters—necessary to understand exposure levels in test systems and the natural environment—was identified as a major knowledge gap in the 2022 report.

Other key issues identified in the 2022 report include the need to better understand exposure and testing dosages, to track degradates and downstream effects, and to develop methods to understand or mitigate the potential for contamination from laboratory testing equipment. The committee also identified a need for methods or benchmarks for measuring acute and chronic toxicity, for better understanding bioaccumulation levels, for characterizing species sensitivity distributions for acute and chronic exposures, and for conducting toxicity tests for nonstandard marine and benthic organisms. The committee also stressed that UV filters do not enter the environment in isolation but within chemical mixtures, pointing to a need to understand the interactions between different chemical components and elucidate the role of coatings, such as silica or aluminum, that are often used with UV filters. Finally, Menzie noted that understanding the impact of UV filters on ecosystems will need to account for the role of other aquatic environmental stressors such as climate change, with particular attention to potential impacts on threatened and endangered species and complex interconnected ecosystems like coral reefs.

The 2022 report included two main recommendations. First, it urged the EPA to conduct ERAs for all currently marketed UV filters and any new ones that become available. The 2022 report outlines critical considerations for these ERAs and noted that the results should be shared with the U.S. Food and Drug Administration (FDA) so that the FDA may include consideration of the environment in its oversight of UV filters in the context of consumer products.

Second, the 2022 report recommended that the EPA, partner organizations, sunscreen formulators, and UV filter manufacturers should conduct, fund, support, and share research and data on sources, fates, environmental effects, bioaccumulation, modes of action, and ecological and toxicity testing of UV filters, alone and in sunscreen formulations. In addition, the 2022 report

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² Organic UV filters include aminobenzoic acid, avobenzone, cinoxate, dioxybenzone, ecamsule, ensulizole, homosalate, meradimate, octinoxate, octisalate, octocrylene, oxybenzone, Padimate O, sulisobenzone, and trolamine salicylate; inorganic UV filters include titanium dioxide (TiO2) and zinc oxide (ZnO).

³ Arnot, J. A., & Gobas, F. A. P. C. (2006). A review of bioconcentration factor (BCF) and bioaccumulation factor (BAF) assessments for organic chemicals in aquatic organisms. Environmental Reviews 14, 257–297. http://dx.doi.org/10.1139/A06-005.

⁴ Schwarzenbach, R. P., Gschwend, P. M., & Imboden, D. M. (2016). Environmental Organic Chemistry. John Wiley & Sons.

committee noted that epidemiological risk modeling and behavioral studies are needed to better understand human health outcomes from changing sunscreen availability and usage.

The committee also offered recommendations regarding guidelines for laboratory saltwater experiments; studies of critical body residues for acute and chronic exposure, bioaccumulation, and toxicity; new approaches and methodologies; and robust chemical analytical procedures, such as minimum replicates, standardized collection, extraction, and processing procedures, and quality assurance and quality control measures for both field and laboratory testing to accurately measure UV filter concentrations over time and space.

MANAGEMENT CONTEXT

In its recommendations, the 2022 report committee emphasized the importance of research into the properties and potential environmental impacts of UV filters in order to inform thorough ERAs by the EPA. In addition, many other federal and state agencies may use such data and the resulting ERAs to consider water quality management within a larger context. Gerry Davis (National Oceanic and Atmospheric Administration [NOAA] Fisheries), discussed the environmental management context for ERAs of UV filters and the importance of water quality in general.

Davis’s office manages NOAA Fisheries’ Pacific Islands Region, which includes the largest, most diverse, and most dense coral reefs within the United States’ jurisdiction. NOAA Fisheries also manages four large Marine National Monuments, protected areas comprising some of the last pristine ocean ecosystems and sustaining many endemic and endangered species. Davis stressed that maintaining water quality is essential to the health of both humans and ecosystems and noted that marine systems such as coral reefs are particularly important resources for the global food supply and economy through their impact on fisheries.

NOAA’s role in supporting water quality and ecosystem health stems from three main federal laws: the Magnuson–Stevens Fishery Conservation and Management Act, the Fish and Wildlife Coordination Act, and the Clean Water Act. These laws provide the framework within which NOAA weighs the protection of natural resources like coral reefs in the process of considering permits for activities that might affect them. Many other agencies, such as the Army Corps of Engineers and the U.S. Fish and Wildlife Service, also have meaningful roles in managing water quality across the United States and therefore share NOAA’s interest in a collective effort to establish adequate, accurate, science-based guidelines for UV filters in sunscreen. Since, as he put it, “you cannot manage what you do not know,” Davis said there is great value in advancing research to improve knowledge about the impact of UV filters on water quality and enable ERAs for UV filters that can be used to inform policy development, implementation, and evaluation.

Davis highlighted some specific concerns about the potential impacts of UV filters on coral reefs. Reduced water quality in general, and the addition of UV filters in particular, can disrupt several life stages of the animals that comprise coral reefs. Corals are sedentary organisms and therefore vulnerable to contamination from environmental spikes in water quality and accumulation over time at a fixed site. To manage the impact of sunscreens and other products containing UV filters on corals, Davis said there is a need for water quality standards that are based on knowledge of contamination levels and information about tolerability thresholds, with appropriate consideration for when samples are taken; how UV filters synergize with other contaminants; how lethal or sublethal thresholds are defined; and how factors such as rainfall, wind, and waves affect water dynamics.

Managing the potential impacts of UV filters is further complicated by an overall dearth of knowledge about factors that affect the health of marine ecosystems, uncertainty in understanding

water quality, and the influence of other environmental stressors that are simultaneously affecting these ecosystems. For example, discharges of freshwater effluent into oceans can dramatically change salinity, increase volume and velocity, and transport contaminants, which can not only kill coral, prevent fertilization, or disrupt settlement but also interact with UV filters and potentially lead to synergistic effects. Climate change and associated sea level rise and ocean acidification also further complicate the overall environment in which coral reefs are being affected by UV filters and other chemicals.

Noting that researchers and regulators have succeeded in improving thresholds for other water quality stressors such as herbicides and pesticides, Davis posited that there is a need for similar thresholds for UV filters. Such thresholds will need to be based on formal, well-designed ERAs addressing sublethal effects and threshold values, individually and in combination with other pollutants, Davis said, and to be effective they will need to be supported by meaningful and enforceable standards appropriate bodies can use to measure and manage water quality. He added that strong federal support will be needed to help local governments develop and enforce standards.

New tools have made it easier to evaluate the health of living resources and make adaptive changes, a marked improvement over using mortality alone to measure water quality. However, Davis said that capacity, funding, and policy remain obstacles to effectively monitoring and managing water quality. He suggested that greater coordination between federal action agencies and NOAA is needed to overcome these obstacles and identify reasonable, affordable alternatives that keep UV filters out of the water, such as UV-protective clothing. Davis said that managing product availability is likely easier than removing UV filters from water, although he noted that such an approach may be vulnerable to industry litigation.

Finally, although sunscreens have garnered national attention, Davis stressed that water quality is about much more than one product. He urged a broader focus on encouraging collaboration and coordination across federal, tribal, state, and local organizations to more fully address the bigger picture and encourage projects that improve climate resilience and coastal water quality.