8

Conclusions and Recommendations

As described in the previous seven chapters, this report contains information for policy makers, scientists, and the public regarding issues to consider in making decisions about the use of UV (ultraviolet) filters in sunscreens—decisions that could have consequences for environmental and human health. These decisions regarding UV filters will be informed by further analysis of the available data along with collection of any additional data deemed necessary to conduct ecological risk assessments (ERAs). They will also be informed by legal and regulatory frameworks and potential value judgments outside of the committee’s scope to review. Although the committee was not tasked with conducting an ERA, this report provides summaries of the information that may be useful when assessing the ecological risks of UV filters. The report provides a state of knowledge summary and identifies data gaps pertinent to (1) the potential that one or more of the active constituents of currently marketed sunscreen products may be harmful to aquatic ecosystems, and (2) the potential that changes in availability of certain UV filters for use in sunscreen products might increase human risk for UV-related harm.

There are many dimensions to considering sunscreens (and specifically, their UV filters) as part of a suite of measures to protect people from harmful effects of solar radiation while minimizing impacts to the environment (Figure 8.1). Some dimensions relate to a sunscreen’s human health benefits, safety, availability/pricing, and likelihood of use; others relate to protection of aquatic organisms and associated ecosystem services such as economic and cultural considerations. The dimensions ideally converge to provide an outcome that is protective of people and the environment. Addressing the statement of task, the committee focused on dimensions related to environmental risk and to the benefits of sunscreen use. Other dimensions are outside the purview of this report, specifically an in-depth analysis of human safety data regarding sunscreen use. Whether a satisfactory or ideal convergence across these dimensions can be achieved with the UV filters currently approved in the United States or will require industry innovation and/or U.S. Food and Drug Administration (FDA) expansion of its list of designated GRASE (generally recognized as safe and effective) status for additional UV filters is outside the scope of this committee.

SUMMARY OF INFORMATION ON EACH UV FILTER

The committee’s review of the scientific state of knowledge highlighted variability across UV filters in their physico-chemical properties and resulting environmental behavior, exposure, and effects, as well as in the amount and utility of the information available to assess them. The committee has summarized what is known about UV filters in Table 8.1. This table can be used as a starting point for identifying similarities and differences across UV filters or identifying indicators of concern to select priorities for further investigation. However, there are varying degrees of uncertainty in the information available, with some of the determinations in the table based on single or few studies (or data points), or studies with varying degrees of relevance and/or reliability of the data. The most information is available for the inorganic UV filters, zinc oxide and titanium dioxide, though there are still gaps in knowledge, especially for marine species. The amount and quality of information available varies among the organic UV filters, with the benzophenones, particularly oxybenzone having received the most attention, and others having almost no data available to review beyond assessments based on their physico-chemical properties (aminobenzoic acid, cinoxate, meradimate, trolamine salicylate). Box 8.1 provides brief summaries of each UV filter based on information from Table 8.1. Box 8.1 reflects the attributes UV filters exhibit on their own, and not how their presence as part of mixtures or formulations may influence their environmental inputs, fates, and effects.

CONCLUSIONS

The committee presents here areas for which there is available scientific information of varying degrees of strength. These conclusions are high-level summaries to accompany the more detailed breakdown by UV filter found in Table 8.1 and Box 8.1.

1. Fate Characteristics: Based on their physical and chemical properties, some UV filters have the potential to remain and accumulate in aquatic ecosystems. Specifically, avobenzone, dioxybenzone, ecamsule, ensulizole, and octocrylene have been shown to have low rates of biodegradation in laboratory settings. However, empirical evidence of rates of degradation and dissipation in the environment are limited as are solubility estimates, particularly in seawater. Inorganic UV filters (zinc oxide, titanium dioxide) are expected to aggregate in the water column and deposit in sediments. Environmental characteristics of receiving waters will also influence the fate of UV filters including physical mixing, advection, light intensity and spectral range, and dissolved organic matter (see Chapter 4). Likewise, depending on compound-specific lipophilicity, environmental compartmentalization and species-specific location and metabolism, some UV filters (avobenzone, octocrylene, oxybenzone, homosalate, padimate O, titanium dioxide, zinc oxide) and/or their metabolites were found to be present in tissues of aquatic animals and plants; however, bioaccumulation studies suggest that bioaccumulative transfer to higher levels of the food web are limited (see Chapter 5).
2. Environmental Occurrence: Measurements of UV filters in surface waters and sediments along with modeling efforts reveal spatially and temporally variable patterns, some of which have been shown to reflect the degree of human activity locally present (i.e., recreation) in addition to the physico-chemical characteristics of the aquatic systems and UV filters. This pattern of exposure is based on analysis of the UV filters with the most environmental measurements (oxybenzone, followed by octocrylene and octinoxate), though even these measurements are typically snapshots in space and time. Current sampling programs are limited, especially in regard to identifying sources, a particular problem for the inorganic UV filters. Maximum observed concentrations of some UV filters can exceed 1 μg/L (ppb) with the highest concentrations found in surface waters immediately off beaches at semi-enclosed embayments. UV filters also enter aquatic systems through treated or untreated wastewater. Treatment can degrade and/or differentially remove a portion of the UV filters present in influents (most likely to be removed are homosalate, meradimate, octocrylene, octinoxate, octisalate, padimate O, titanium dioxide, and zinc oxide based on Kow and laboratory testing), with some of these being translocated to sewage solids. The measured concentrations for water bodies receiving wastewater effluent have been generally lower than for waters with recreational activities, though the environmental setting is expected to be a factor (see Chapters 3 and 4). Measured concentrations do not necessarily reflect UV filters solely from sunscreen, as they are present in a range of products, with other personal care products being the category of product most likely to have similar fates as sunscreens (see Chapter 2).
3. Environmental Effects: For most UV filters, acute toxicity information is available for standard algal, invertebrate, and fish species, though in some cases data from only one to two studies per taxa are applicable for use in an ERA (chronic data is limited across UV filters). Data are limited for nonstandard but important ecological receptors, particularly marine species, often challenged by the lack of standard toxicity test methods and the use of important but nonstandard endpoints (e.g., bleaching and/or algal loss in corals). Many UV filters have either laboratory observations or QSAR estimates of acute toxicity under 1,000 μg/L. However, toxicity results range widely for most UV filters and in some cases, only a few studies support toxicity below 1,000 μg/L. For the UV filters with low solubility, results are typically above solubility, indicating a need for chronic studies of lower exposure concentrations. Supporting toxicological information

TABLE 8.1 Characteristics of UV Filters

NOTES: Color coding reflects relative magnitudes of entries. Orange = Higher or Yes, Yellow = Moderate, Blue = Lower or No.

3. has been developed using cell-line tests and other studies that can help elucidate toxic modes of action (e.g., narcosis, endocrine disruption, enzyme inhibition), which may be useful for informing assessments if they can be linked through adverse outcome pathways to population endpoints used for ERA. Studies on effects on community interactions and ecosystem processes are largely absent and, at this time, are mostly presumed based on effects on taxa involved in key community and ecosystem functions. Spatial overlap is expected between habitats occupied by threatened and endangered species and UV filter exposure zones, and effects will depend on magnitudes of exposure and the sensitivity of the species (for which little is known) (see Chapter 6).
4. Multiple UV Filter and Stressor Context: Risks that UV filters may pose to aquatic ecosystems will occur within the context of other global (e.g., climate change variables) and local stressors (e.g., pollution, physical damage). Ecological risk assessments commonly consider chemicals individually, which is appropriate. However, there are two aspects associated with multiple stressors and their potential for antagonistic, additive or synergistic effects that are important to consider when planning an ecological risk assessment for UV filters: (1) the possibility of mixture effects of multiple UV filters and (2) possible interactions of UV filters with other predominant environmental stressors (e.g., temperature, UV light, salinity, other contaminants). UV filters that co-occur in products or in the environment are candidates for considering possible mixture-related effects and risks. Among the global predominant stressors on aquatic ecosystems, increasing temperature has been shown to be a major stressor on its own, but it is also known to exacerbate the effects of toxicants and is important to consider when assessing effects and risks from UV filters in aquatic environments (see Chapter 6).
5. UV Radiation and Sunscreen Benefits: Exposure to UVA and UVB radiation increases the risk of both acute and chronic injury to humans. Acute effects are inflammation, usually referred to as sunburn. Chronic effects include malignant melanoma, basal cell and squamous cell cancers, photoaging, and a host of precancerous changes to the skin. The burden of skin cancers in terms of disease, death, and health care costs is high and melanoma rates are increasing. Also, there are specific photosensitive conditions for which exposure to UV radiation is more harmful. These relationships have been established by extensive epidemiologic studies, largely conducted in fair-skinned populations. Consistent use of SPF 30 broad-spectrum sunscreens has been shown experimentally and in observational studies to reduce risk for melanoma, squamous cell skin cancer, sunburn, and photoaging. The overall level of certainty regarding these benefits is high (see Chapter 7).
6. Sunscreen Usage and Preferences: Behavioral studies have found that the use of sunscreen for photoprotection is inadequate. It is not used by all who should use it, too little is used, and/or not reapplied frequently enough. It has been found from usage data, internet product reviews, and surveys that individuals prefer sunscreens with high SPF and various cosmetic features. Of particular relevance with regard to cosmetic aspects is that some consumers will have a lower preference for preparations containing inorganic filters (studies on preferences do not distinguish particulate sizes) in the concentrations needed when these agents are used alone without organic filters. However, studies have also found that many consumers lack knowledge of the active ingredients in their preferred sunscreens (see Chapter 7).
7. Implications of Changing Sunscreen Use: Reduced availability of consumer-preferred sunscreen formulations may lead to reduced use of sunscreens. Human health outcomes will depend on the available UV filters, which will drive both consumer use and sunscreen efficacy. Educational and motivational campaigns that encourage the use of broad-spectrum SPF 30+ sunscreens at recommended levels along with other photoprotective behaviors where feasible, as well as implementation of environmental supports such as public shade structures, may mitigate these harms (see Chapter 7).

RECOMMENDATIONS

The variable characteristics and information available for each UV filter suggests a tiered approach to ecological risk assessment for evaluating the suite of UV filters. Tiered approaches typically include an initial screening step that serves to place compounds in various bins based on known characteristics and available data on exposures and effects. Screening can serve to differentiate among chemicals that may pose a risk, clearly do not pose a risk, or require additional information in order to conduct a more thorough evaluation. Chemicals that may pose a risk can be analyzed in more depth (i.e., a higher tier analysis) to address uncertainties or aspects of evaluating exposure and/or effects. In some cases, higher tier analysis involves additional exposure modeling, measurements, and/or toxicity testing. The initial screening step can help prioritize UV filters for further evaluation and help guide data collection efforts needed to reduce uncertainties that impact reliable risk management decisions. To this end, there are compelling reasons to prioritize efforts to reduce data gaps, based on physico-chemical and toxicological properties, or in some cases, a near-complete lack of information.

Recommendation 1: The U.S. Environmental Protection Agency should conduct an ecological risk assessment (ERA) for all currently marketed UV filters and any new ones that become available. There is an urgent need to conduct such an assessment, driven by the evidence of local exposures of aquatic organisms in U.S. aquatic ecosystems to UV filters, potentially including endangered species, and experimentally demonstrated potential for environmental impact, either alone or in context of other system stressors. The results of the ERA should be shared with the U.S. Food and Drug Administration for their consideration of the environment in their oversight of UV filters. The following points are critical for conducting an ERA for UV filters:

• The ERA is expected to include information from acute and chronic toxicity studies with standard test species and life stages, methodologies, and biological endpoints. However, nonstandard species and additional biological endpoints should also be considered given the diversity of important ecological species potentially exposed to UV filters and the potential for adverse effects not captured in standard test protocols (e.g., corals and their unique endpoints related to bleaching). While not currently used for regulatory ecological risk assessments in the United States, cell-line tests and other New Approach Methods such as molecular/biochemical changes may be useful for elucidating toxic modes of action (e.g., narcosis, endocrine disruption) and potential for effects.
• Because UV filters often occur in mixtures within products and in varying compositions across products, ERAs should not only consider UV filters individually, but also evaluate the potential for risks from co-occurring UV filters. Mixture considerations could be based on co-occurrence in the environment, as well as common exposure pathways and modes of action.
• ERAs should consider the environmental settings or exposure scenarios, specifically the potential for localized (in space and time) elevated UV filter concentrations in the water column and/or sediment that provide habitat for a diverse or unique biological community. Settings to give particular attention to are (1) coral reefs in shallow near-shore environments with heavy recreational use and limited transport/flow of seawater and/or colocated near communities where wastewater and urban runoff may enter the marine environment, and (2) lentic (slow-moving) freshwater systems with heavy recreational activity or wastewater effluent and high water residence time, especially the habitats of sensitive species such as amphibians and mussels.

While conducting an ERA in the near-term is imperative, future assessments will be improved by increased data collection. Knowledge gaps have been outlined in each chapter.

Recommendation 2: The U.S. Environmental Protection Agency, partner agencies (e.g., Centers for Disease Control and Prevention, U.S. Department of the Interior, U.S. Food and Drug Administration, National Institutes of Health, National Oceanic and Atmospheric Administration, National Science Foundation), and sunscreen formulators and UV filter manufacturers should conduct, fund or support, and share research

and data on sources, fate processes, environmental concentrations, bioaccumulation studies, modes of action, and ecological and toxicity testing for UV filters alone and as part of sunscreen formulations. Additionally, epidemiological risk modeling and behavioral studies related to sunscreen usage should be conducted to better understand human health outcomes from changing availability and usage. Coordination among these organizations would improve collection of the various types of relevant data needed for an ecological risk assessment. Future research should adhere to international or national standards where applicable for analytical chemistry and toxicological studies, and follow accepted principles for ensuring good quality information from testing and measurement protocols, report their methodologies, and undergo scientific peer review of both protocols and findings for quality assurance. This may include new national/international standards for toxicity testing on relevant species and the addition of non-traditional biological endpoints for acute and chronic toxicity. Public access and transparency in all data and research outcomes is critical for assurance of public and environmental health.

MANAGING HUMAN AND ENVIRONMENTAL HEALTH

Any policy and management actions taken will require consideration of their human and ecological outcomes and coordination across multiple agencies and organizations to develop creative solutions. The committee does not recommend which (if any) actions should be taken in regard to UV filters used in sunscreens. The recommendation to proceed with an ecological risk assessment is directed toward EPA, the sponsor of the study. The committee is mindful that FDA is developing an Environmental Impact Statement that can draw on information presented in the committee’s report and from subsequent work conducted by EPA. Other than the procedures established by the National Environmental Policy Act, mechanisms for joint decision making across agencies that can facilitate decisions that consider human and environmental health aspects of sunscreens and UV filters together, are not clearly established. However, such coordination is critical for addressing the human and environmental dimensions of this topic, the purview of which reside in multiple agencies. An example approach to cross-agency (as well as industry) coordination on an issue impacting human and environmental concerns is the Federal Task Force on Combating Antibiotic-Resistant Bacteria, which has collaboratively recommended approaches to managing antibiotic use while still recognizing the critical need to use antibiotics to fight bacterial infections (Federal Task Force on Combating Antibiotic-Resistant Bacteria, 2020). Ultimately, finding solutions that respect and minimize harm to the environment while maximizing concern for human health will require cooperation, rigorous and transparent aquatic and human science, and open dialogue among scientists, health professionals, and cross-sectoral government agencies and non-governmental organizations.

UV filter application to skin is a critical strategy toward protecting humans from skin cancer. Research on UV filters in the environment as well as human behavior regarding the use of sunscreen is a rapidly growing field, and the state of knowledge will quickly surpass what is described in this report. The committee’s recommendation to proceed with collaborative research and data provision from manufacturers will serve to address important data gaps. Further knowledge will continue to accrue regarding the differential potential for ecological harm of available UV filters and optimal strategies to enhance societal application of UV protection to reduce health risks to inform the dual goals of protection of environmental and human health.

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