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Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
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2

Introduction to Sunscreens and Their UV Filters

This chapter provides an overview of the UV (ultraviolet) filters used as the active ingredients in sunscreens marketed in the United States. UV filters are a diverse set of chemicals with varying physical and chemical properties that influence their presence, behavior, and toxicity in the environment. This chapter introduces some of the basic properties of the UV filters; a more complete explanation of their environmental fate can be found in Chapter 4. What UV filters all share is the ability to absorb, reflect, and/or scatter UV radiation. The modes of action for UV absorption and reflection/scattering are described in this chapter.

Sunscreens are a complex mixture of active and inactive ingredients, and can be found in various forms (e.g., lotions, sprays, roll-ons). The effectiveness of sunscreen is determined by the combination of UV filters and inactive ingredients. Important considerations for formulations such as SPF (sun protection factor), broad-spectrum coverage, photostability, substantivity, and cosmetic appeal are described in this chapter. These considerations drive the requirements that need to be met by the combination of UV filters available for use in marketed sunscreen products.

Last, this chapter explores the available data related to production volumes of UV filters. Production and sales data are a typical starting point for understanding the scales at which UV filters may enter the environment and establish a need for further investigation. Additionally, UV filters can be found in more products than sunscreen, including other personal care products as well as a wide range of other consumer and industrial products, which may contribute to environmental inputs. This chapter explores what is known about the relative usage of UV filters in sunscreens compared to other products. Understanding this distinction can inform targeted management measures for any UV filters identified to pose an environmental risk.

PHYSICAL AND CHEMICAL PROFILES

The chemicals used as UV filters vary in their physical and chemical properties, which influence both their environmental fate and potential toxicity as well as their contributions to skin protection. The most significant difference is that two of the UV filters approved for use in the United States are inorganic particulates (titanium dioxide [TiO2] and zinc oxide [ZnO]) while the other UV filters are organic chemicals. Notably, as particulates, the inorganic UV filters can be found in a variety of shapes and sizes (though their different forms are not distinguished in their regulation as UV filters), leading to more variability in their environmental behavior than is seen in organic UV filters.

The physico-chemical properties of organic chemicals largely drive environmental behavior (i.e., fate and effects) in the environment and therefore information about these properties is generally required before conducting

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
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an environmental risk assessment. These properties are more thoroughly reviewed in Chapter 4, but are briefly described here. Solubility of a chemical is used to estimate relevant dosing levels in aquatic toxicity tests since it is uncommon that environmental exposure exceeds solubility (except in certain scenarios such as acute spill events). Solubility varies between marine and fresh water and there are no standardized protocols for measuring solubility in these environments. It can also depend on the pH of the water or the pKa (acid dissociation constant) of the chemical. Hydrophobicity is a means to describe the tendency of a chemical to move into or partition out of water (such as by adhering to sediments or organic matter). It is often evaluated using the octanol:water partition coefficient, or log Kow (i.e., high Kow chemicals are lipophilic and hydrophobic). Volatility is related to the propensity of some organic chemicals to transfer from a condensed phase (solid, liquid) to the gas phase. The propensity of an organic chemical to transfer from water to air is described with Henry’s law constants, which describe the equilibrium ratio of the concentrations of a chemical in water versus the gas phase. Collectively, these properties define—when a chemical is released into the environment—where it may ultimately reside (i.e., air, water, sediment). ECETOC (2013) provides a comprehensive summary of how these physico-chemical properties are related and impact environmental exposure, thereby influencing both ecotoxicity and assessment of environmental risk.

Many of the drivers of environmental behavior for organic chemicals do not apply to inorganic particulates. Most metal oxides are not soluble in water, though they may break down into water-soluble ions. Microparticulates of TiO2 and ZnO have been used in sunscreens for over 35 years (Buchalska et al., 2010; Gasparro et al., 1998). However, in the last decade the use of nanoparticulate (less than 100 nm in size) forms are increasingly being incorporated into products due to their less opaque appearance in the skin than their larger counterparts (Labille et al., 2010; Smijs and Pavel, 2011). In contrast to organic UV filters that have fixed chemical structures, inorganic UV filters have a wide variety of shapes with differing aspect ratios from spherical to elongated tubular shapes and may be composed of hybrid mineral structures that include aggregates of particles or films coating the active UV filter. For example, Figure 2.1 shows ZnO nanorods with smaller TiO2 nanoparticles that were extracted from an over-the-counter sunscreen product. The wide variety of mineral-based UV structures may complicate mechanistic understanding of fate, transport, and biological effects (Zheng and Nowack, 2021), and limited predictive science relating to these types of particles in complex water chemistries complicate the ability to allocate specific sources of these UV filters in the environment. Furthermore, these inorganic UV filters are often associated (coated) with other chemicals that also change their physico-chemical properties and hence potential fate and effects in the environment. Coatings on inorganic UV filters can be made from aluminum, silica, or other inorganic forms and/or with organic polymers (Philippe et al., 2018). These coatings serve at least two functions. First, they retain and quench reactive oxygen species that can be produced by photoexcitation in sunlight from UV wavelengths of light. Second, they modify the surface charge of the particulates to improve dispersion within the inactive ingredients.

Degradation Products

As will be described further in Chapter 4, organic UV filters are subjected to complex abiotic (e.g., photolysis, hydrolysis) and biotic (e.g., biodegradation, metabolic transformation) processes that can form innumerable degradation products. For example, abiotic processes include alterations in UV filters due to UV light. Photolytic transformation of UV filters occurs directly (through photolysis, where the UV filter itself absorbs light and subsequently transforms) and indirectly (where the UV filters may react with a reactive species that is generated from other chemicals, called photosensitizers, present in the water column). Biotic processes occur within microorganisms (often termed biodegradation) or other organisms through metabolic pathways that transform the parent UV filter into any number of products. Metabolites formed during biodegradation are known to occur in waste treatment (see Chapter 3) and under natural environmental conditions (see Chapter 4). Algae, invertebrates, fish, and mammals have each shown capacities to transform specific UV filters to various degrees. The fate and toxicity of degradates may be different from their parent compounds.

The statement of task asks the committee to consider “applicable degradates” as part of its review of UV filters. However, it is not possible in this report to summarize the plethora of possible degradation products for organic UV filters. One study with oxybenzone alone reported the potential for more than 20 metabolites in fish (Ziarrusta et al., 2018a). Additionally, relatively few metabolites have been studied in isolation; thus, making broad

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
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FIGURE 2.1 Examples of shapes and sizes of titanium dioxide (TiO2) and zinc oxide (ZnO) particles from sunscreens imaged by transmission electron microscopy. (a) Amorphous ZnO, (b) mixture of TiO2 and rod-shaped ZnO, (c) TiO2 from an aerosol sunscreen, and (d) TiO2 from a commercial sunscreen. SOURCES: (a) and (b) Hanigan et al. (2018); (c) and (d) Courtesy of committee member Paul Westerhoff.

conclusions on the relative importance of degradation products in the context of UV filter exposure will be challenging and will likely rely on modeling to make projections of their relative metabolism, bioaccumulation, and ecotoxicity potential. What is clear is that UV filters will be present as mixtures of parent compounds and their associated metabolites to some degree in nearly all environmental scenarios.

Inorganic UV filters may dissolve into ions which will influence their fate, bioavailability, and ultimate toxicity (see Chapter 6). TiO2 is unlikely to dissolve in most environmental water matrices and requires intensive acid and heating to degrade into titanium ions during chemical analysis (Peters et al., 2018). However, there is experimental evidence that low levels of ionic titanium can be released from TiO2 (Holbrook et al., 2013). In contrast, ZnO minerals are predicted by thermodynamics to dissolve in water and have been experimentally observed to dissolve more rapidly at lower pH levels (Wu et al., 2019a,b) and rates can be influenced by ionic composition in water (Reed et al., 2012). Additionally, surface coatings on inorganic UV filters may degrade, which would alter

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
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their tendency to aggregate or settle and their ability to participate in redox-mediated reactions, or slow down the dissolution of TiO2 or ZnO.

MODES OF ACTION FOR SKIN PROTECTION

UV filters protect the skin from the negative consequences of UVA (315–400 nm) and UVB (280–315 nm) exposure including sunburn, photoaging, and skin cancer (Chisvert and Salvador, 2007; Giokas et al., 2007)—with each UV filter protective within a specific UV range. The ability to protect skin from ultraviolet sunlight as well as the exposure and toxicity potential of these UV filters are related in part to their chemical structures.

Most of the organic sunscreens contain aromatic carbon and/or other electron-dense bonds that are responsible for absorbing light in the UV ranges of the solar spectrum. Energy from UV radiation excites electrons in the UV filters. This energy is released as a negligible amount of heat rather than affecting the skin (Nash and Tanner, 2014; Shaath, 2007). An electron in a photostable chemical will normally return to its ground state, able to repeat the process. However, UV filters have varying degrees of photostability and this process can instead produce photodegradation products (including isomers) as well as reactive oxygen species, and reduce the concentration of UV filters over time.

Figure 2.2 shows the chemical structure of the organic ingredients listed in Table 2.1. Broadly speaking, the organic UV filters can be grouped according to their chemical structures. The benzophenones, which include oxybenzone, dioxybenzone, and sulisobenzone, all contain aromatic methoxy moieties on a benzophenone backbone. Avobenzone is similar to the benzophenones, with the key difference being the linkage between the aromatic rings. Most of the other organic UV filters contain aromatic esters, including the salicylates (octisalate, homosalate, and the salt trolamine salicylate), the cinnamates (octinoxate and cinoxate), meradimate, octocrylene (which is similar to the cinnamates), and the aminobenzoates (padimate O and aminobenzoic acid). For the UV filters approved for use in the United States, ensulizole and ecamsule are the structural outliers in that their organic structures contain neither aromatic esters nor aromatic methoxy moieties. These two organic UV filter chemicals do, however, both contain sulfonic acid moieties (as does sulisobenzone).

The two inorganic UV filters interact with UV light by two mechanisms: absorption and reflection/scattering. Both ZnO and TiO2 are semiconductor materials that allow light to be absorbed. In fact, approximately 85 to 95 percent of UV radiation is actually absorbed by inorganic UV filters (Cole et al., 2016). Similar to organic UV filters, UV radiation excites an electron into a higher energy orbital state (Smijs and Pavel, 2011). Specifically, overlapping electron orbitals in the crystalline structure form “bands,” with gaps between energy bands (“band gap”). Electrons are excited across the band gap from a lower valence band into a higher conduction band. Particle size and composition influences the amount of UV radiation that is absorbed or scattered/reflected. Larger particles reflect/scatter more UV radiation than smaller ones, though for all particles absorption is still a dominant mechanism. Smaller, nanoscale particle UV filters reflect less visible light, and therefore appear nearly transparent in color, compared to the whiter appearance of larger particles. Reducing particle size also shifts the UV wavelength range that the particles are protective against.

UV FILTERS IN SUNSCREEN FORMULATIONS

To claim protection from skin cancer and early skin aging,1 products labeled as sunscreen in the United States are required by the U.S. Food and Drug Administration (FDA) to be broad spectrum and have an SPF of at least 15.2 SPF is a metric of the UV radiation required to result in sunburn in skin protected with sunscreen (when used in amounts and application rates as directed) relative to that required to result in sunburn in skin without sunscreen (FDA, 2017). Sunburn is caused by UVB radiation and thus SPF is a measure of UVB protection. According to FDA rules, to be labeled as broad spectrum, a product must have a critical wavelength of at least 370 nm, meaning

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1 Specifically, labeling may claim “if used as directed with other sun protection measures … decreases the risk of skin cancer and early skin aging caused by the sun” (from Over-the-Counter Monograph M020: Sunscreen Drug Products for Over-the-Counter Human Use).

2 Different regulations related to effectiveness testing and labeling may apply outside the United States.

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
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FIGURE 2.2 Chemical structures for organic UV filters available in the United States. SOURCE: Chemical structure images from ChemSpider.com.
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
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TABLE 2.1 UV Filters and Their UV Protection Range and Maximum Allowed Concentration in U.S. Sunscreen Formulations

UV Filter Protective Range (UVA1/UVA2/UVB)a Maximum Percentage Concentration (Weight per Volume)b
Aminobenzoic acid UVB 15
Avobenzone UVA1 3
Cinoxate UVB 3
Dioxybenzone UVA2, UVB 3
Ecamsule UVA1, UVA2 Approved for specific formulations only
Ensulizole UVB 4
Homosalate UVB 15
Meradimate UVA2 5
Octinoxate UVB 7.5
Octisalate UVB 5
Octocrylene UVB 10
Oxybenzone UVA2, UVB 6
Padimate O UVB 8
Sulisobenzone UVA2, UVB 10
TiO2 UVA2, UVB 25
Trolamine salicylate UVB 12
ZnO UVA1, UVA2, UVB 25

a Shaath (2007). Categorization as a UVA or UVB filter depends on interpretations of variations in absorbance along the UVA and UVB spectrum and in some cases may be interpreted and stated differently in different sources.

b From the Over-the-Counter Monograph M020: Sunscreen Drug Products for Over-the-Counter Human Use. Final Administrative Order (OTC000006).

90 percent of the product’s total absorbance must be at or above this value when measuring from 290 to 400 nm (21 CFR 201.327). UVA protection, particularly UVA1, is not captured in the SPF and broad-spectrum definitions as well as UVB protection, though both UVA and UVB are associated with skin cancer (see Chapter 7).

Usually, an individual UV filter does not provide protection against the entire UV wavelength range (see Table 2.1). Each UV filter has a UV wavelength range where it is most protective that leads it to be identified as a UVA (which is further divided into UVA1 or UVA2) and/or UVB filter. Most commercially available sunscreens in the United States contain mixtures of UV filters to offer broad-spectrum coverage. Only the inorganic UV filters can provide broad-spectrum coverage on their own, and between the two, only ZnO provides coverage in the UVA1 range (UVA2 coverage influences broad-spectrum labeling more than UVA1). Most organic UV filters provide coverage in UVB ranges while avobenzone provides its strongest coverage in the UVA1 range and the benzophenones (oxybenzone, dioxybenzone, sulisobenzone) provide coverage in UVA2 in addition to UVB. Meradimate also provides UVA2 coverage, though as described later, its efficacy is low. Ecamsule provides UVA1 and UVA2 but is limited to use in certain L’Oréal products (Forestier, 2008). Sunscreens sold in the United States are available in multiple forms: cream, stick, lotion, gel, aerosol and pump spray, foam, butters, pastes, and powder (FDA, 2021a). All forms are effective if used as directed.

The concentration of the UV filter in the sunscreen product influences how protective it is in its wavelength range (Forestier, 2008). Figure 2.3 depicts the absorbance of a selection of commonly used UV filters at 1 percent concentration (in a 1 cm layer). The concentrations of each UV filter will vary in a sunscreen formulation, influencing how much they contribute to UV protection. An “inefficient” UV filter absorbs less UV radiation at

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
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FIGURE 2.3 Absorption profiles for eight commonly used UV filters in the ultraviolet spectrum based on 1 percent concentrations of each UV filter. NOTE: PBSA = ensulizole, all other names follow committee usage. SOURCE: Reynertson, 2021 presentation to committee.

low concentrations than an “efficient” UV filter. The inorganic UV filters are inefficient UV filters (Shaath, 2007; Figure 2.3), but can be included in sunscreens as up to 25 percent of the formulation (see Table 2.2). The salicylates (homosalate, octisalate) are also inefficient UVB absorbers that are used in relatively higher concentrations (for homosalate) and/or in combination with other UVB filters. Meradimate is an inefficient UVA2 filter. While generally protection increases as concentration increases, there may be limits to effectiveness such has been demonstrated for homosalate (measured as SPF contribution) (Couteau et al., 2007b). Additionally, maximum concentrations are regulated by FDA limiting how much a single UV filter can contribute to a formulation, resulting in the use of multiple UV filters especially at higher SPFs (see Table 2.2).

In addition to the specific UV filters used in a formulation, many other compounds are also present to serve as emulsifiers, solubilizers, stabilizers, SPF boosters, and preservatives (Pawlowski and Petersen-Thiery, 2020; Figure 2.4)—all of which influence the protectiveness of the sunscreen. Reviewing the fate and effects of the inactive ingredients is not in the scope of this report. However, it is important to point out that they could potentially impact the environmental behavior of the UV filters. For example, emollients may allow UV filters that are otherwise poorly dissolved in water to be found in the environment in aqueous form, for at least a short duration following direct release. In some cases, these roles are played by other UV filters. For example, avobenzone and oxybenzone must be solubilized to be part of a sunscreen formulation, which can be accomplished through the use of salicylate UV filters or a variety of other solvents.

Photostability of UV filters in sunscreen formulations, meaning their ability to interact with UV radiation without being significantly depleted via degradation before reapplication, is an important contribution to the product’s SPF. Photodegradation can also produce reactive oxygen species that can damage human skin (Kockler et al., 2012). As will be described in more detail in Chapter 4’s discussion of environmental fate processes, the UV filters have varying degrees of stability when exposed to UV radiation. However, photostability can be dependent on solvents and so may differ between aquatic environments and sunscreen formulations (Kockler et al., 2012; Serpone et al., 2002). Notably, photoisomerization of avobenzone to a less stable form occurs in some nonpolar solvents that can be found in sunscreens (Berenbeim et al., 2020; Mturi and Martincigh, 2008; Vallejo et al., 2011). Some of the more stable UV filters include aminobenzoic acid, oxybenzone, octocrylene, and octinoxate,

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
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FIGURE 2.4 Typical composition of a sunscreen and corresponding functions. SOURCE: Pawlowksi and Petersen-Thiery, 2020.

as measured in an oil/water emulsion (Couteau et al., 2007a). However, measuring photostability can be challenging and results can depend on experimental approaches, such as solvents used (Bonda, 2005). Photo-unstable UV filters can be combined with stabilizing compounds (e.g., antioxidants; Kockler et al., 2012) to be used in sunscreen formulations. Notably, the photostability of avobenzone in sunscreen formulations can be improved by the inclusion of the UV filter octocrylene, though it can also be accomplished through the use of other stabilizers (Nash and Tanner, 2014). Conversely, some combinations of UV filters can increase photo-instability (Kockler et al., 2012), such as the negative effect avobenzone has on octinoxate stability (Herzog et al., 2009; Lhiaubet-Vallet et al., 2010; Sayre et al., 2005). Inorganic UV filters are photostable; however, they may act as photocatalysts and increase degradation of organic UV filters or other organic compounds (Ginzburg et al., 2021; Picatonotto et al., 2001; Smijs and Pavel, 2011). The use of coatings or dopants significantly decreases photocatalytic activity, though it may still occur (Kockler et al., 2012).

Substantivity is the ability of a sunscreen to remain on the skin under stress from physical activity, sweating, and swimming (Poh Agin, 2006). The adherence of sunscreens to the skin in a stable film is a factor in their efficacy as well as the extent of their release into the environment. Water resistance is a sunscreen’s ability to maintain its SPF with submersion in water. FDA allows for labeling to indicate either 40 minutes or 80 minutes of water resistance based on specified testing procedures, and prohibits the use of “sweatproof” and “waterproof” (21 CFR 201.327). During perspiration, stress comes from below the sunscreen film. Higher sweat rates lead to a large loss of UV protection through wash-off and redistribution on the skin; larger application doses lead to larger amounts of sunscreen being washed off and redistributed but still with higher sustained UV protection (Keshavarzi et al., 2021). Two formulations with the same type and amount of UV filters can produce very different results depending on the stability of the film in the product (Infante et al., 2021). Polymers are usually added to sunscreens to increase film stability (Puccetti and Fares, 2014). Water-soluble filters provide poor water resistance (Kullavanijaya and Lim, 2005). In addition to wash-off, absorption into the skin reduces effectiveness of a UV filter (a discussion of the relationship between absorption and human safety is included in Chapter 7). Absorption is expected to be reduced in higher molecular weight UV filters or for encapsulated forms of UV filters (Cozzi et al., 2018; Shaath, 2007).

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
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Consumer acceptance of a sunscreen formulation influences protectiveness by encouraging proper use. A sunscreen that spreads smoothly on the skin is more likely to be used properly, and this can be influenced by inactive ingredients as well as the combination and concentration of active ingredients. For example, iron oxide is often added as a tint to sunscreen formulations to improve acceptability of inorganic sunscreens that appear white on the skin (it also can act as a UV filter but is not approved for this use) (Kullavanijaya and Lim, 2005). Additionally, one study found sunscreens containing inorganic UV filters were used in lower quantities per application than sunscreens with organic UV filters (Diffey and Grice, 2008).

The formulation of a sunscreen is driven by how the target SPF and broad-spectrum protection are achieved given tradeoffs in the efficiency of different UV filters (i.e., spectrum coverage, concentrations needed to achieve SPF or to counteract photo instability), costs, and cosmetic appeal (Forestier, 2008; Nash and Tanner, 2014; Shaath, 2007). Specifically, limitations in UV filters can be compensated for by increased concentrations, additional UV filters, or by the inactive ingredients. However, this may result in tradeoffs in cost and cosmetic appeal. The ingredients that provide UVA1 protection—avobenzone and ZnO—provide the clearest example of this tradeoff and are an important case to consider given the limited UV filters active in this range. ZnO is a highly stable broad-spectrum UV filter, but requires use in higher concentrations for effective protection and appears white on the skin if used in non-nano forms. Avobenzone is the only organic UVA1 filter approved for broad use in the United States (other than the proprietary use of ecamsule) and may have more consumer cosmetic appeal, but requires additive ingredients to promote photostability and dissolution in the formulation (which may or may not be served by other UV filters). Developing combinations of ingredients depends on understanding their complex interactions (Pawlowksi and Petersen-Thiery, 2020). Additionally, a small population of consumers have photoallergies to various organic UV filters (as well as inactive ingredients like fragrances)—especially benzophenones, avobenzone, or octocrylene (Heurung et al., 2014; Keyes et al., 2019; Scheuer and Warshaw, 2006), further necessitating choice among products. The result of these factors is a wide selection of formulations on the market to cater to the needs and preferences of different users. Sunscreen formulations can also be proprietary or patented, leading to more variability among formulators (Shaath, 2007).

Viewing UV filters as part of sunscreen formulations also has implications for understanding environmental risk. Ecological risk assessments for regulatory purposes are typically single-compound evaluations and represent the norm for regulatory compliance. However, due to the complex formulations of sunscreens and the variability across products that may end up in the environment, UV filters will appear in the environment as part of mixtures, at least initially. And as noted earlier, inactive ingredients can influence the behavior (solubility, photostability) of UV filters, and their co-occurrence in the environment could potentially influence environmental fate. This leads to complex assessments of environmental effects that may need to address either concentration addition (compounds with same mode of action will add together) or independent action (different modes of action will act partially or completely independent of each other).

INVENTORY AND USES OF UV FILTERS

There are multiple ways to estimate the amount of UV filters present in an aquatic environment. Measurements of the chemicals in the water and sediment establish concentrations at a particular location and time, while measurements within the tissue of organisms indicate how much a substance has bioaccumulated at that time. These measurements are necessary prerequisites for toxicity to occur, but in themselves do not indicate harm. However, these measurements are a critical part of the risk assessment process and are described in Chapters 4 and 5 of this report. Estimating sunscreen usage by people is another method to address inputs into the environment from sunscreen specifically. For example, estimating how much sunscreen is used by an average person during beach activities, multiplied by the number of people visiting a beach at a time and quantifying how much may wash off in the water—this provides a rough estimate of how much sunscreen may enter the water. However, estimating how much sunscreen people use is a challenge, as many people do not follow recommended application amounts or rates of reapplication (reviewed in Chapter 7). Additionally, sunscreens are composed of an assortment of UV filters that complicate this estimate for any individual UV filter.

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
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Understanding the overall quantities of the chemicals produced, sold, and used in a given area provides a broader means to assess environmental distribution. Total volumes of production, sales, or usage are a typical starting point for establishing the need for further investigation into potential risks. Additionally, measurements of occurrence in the environment do not provide information about the source of the UV filters—either their means for entering the environment (e.g., wastewater or direct input via recreational use) or the product from which they originated (e.g., sunscreen, other personal care products, or household or industrial products). Knowing the sources and their relative contributions aids in developing appropriate and targeted control strategies.

The following section describes what is known about production volumes of UV filters, products that contain UV filters, and the relative mass of UV filters in sunscreens compared to other products. The source of these estimates is either from manufacturers’ reports of products containing UV filters to regulatory bodies or aggregated market data, and can be accessed through various databases. These data sources are limited to what manufacturers are required to report and other caveats of each dataset (described in the next section) and will differ from each other as a result; proprietary industry information is otherwise difficult to obtain.

General Sources of Information

The most rigorous approach to gain tonnage data is to combine sales and marketing data (sales per product, product line, and manufacturer) with the percentage of an individual UV filter used in products to directly determine tonnage per UV filter per manufacturer (Mudge et al., 2012, 2014). Sales data are proprietary, but with information on sales, percent in product, population used, and time can be used to determine a per capita use rate (i.e., the mass of the chemical used per person per day). The value of these collective usage estimates is that they can assist screening models for projecting exposures “down the drain” (i.e., received and discharged by wastewater treatment plants, described further in Chapter 4), identify areas of focus and complexity to obtain better data, and assist prioritization of compounds when compared with effects and monitoring data. However, these tonnage estimates (and therefore subsequent models) do not capture variability of usage by different people and in different locations (e.g., beaches). Challenges to understanding UV filter usage amounts include the diversity of uses of each compound, confidentiality of industry information, temporal shifts in manufacturer use, and completeness of information found in inventories. All of these challenges contribute to uncertainty regarding usage. Therefore, the estimates discussed here can be a screening tool for further assessment.

The following are sources of data for amounts and usages of UV filters. Notably, several sources are regulation-driven reporting, and thus regulatory bodies like the U.S. Environmental Protection Agency (EPA) have greater ability to collect data and review confidential information useful in ecological risk assessment than this committee. The committee focuses here on information pertinent to the United States, supplemented by usage information available from the European Union. While European data will not be reflective of amounts or exact product categories used in the United States, and there is not complete overlap in the UV filters used in each location, they may still be used as an indicator of the approximate or relative amounts of UV filters used in consumer products. Accessing volume of use data from other countries is more challenging, though many other countries have adopted the list of permitted filters used in the European Union as an effort to improve regulatory harmonization and could potentially have similar relative usage amounts (Pirotta, 2020). The available data are reviewed here to provide insights about sources of UV filters to be informative to the committee’s higher-level assessment.

  1. EPA Chemical Data Reporting (CDR)3: Manufacturers and importers of substances regulated by the Toxic Substances Control Act (TSCA) are required to report types, quantities, and uses of chemical substances produced domestically and imported into the United States to the EPA. CDR data is used by EPA for risk screening, risk assessment, chemical prioritization, risk evaluation, and risk management activities. Reporting via the CDR process is required when volumes produced at a manufacturing site reach 25,000 pounds (11.3 mt). Reporting occurs once every four years and is most recently available from 2016 for reporting years 2012–2015. If a portion of a manufacturer’s production is not subject to TSCA, then the

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3 See https://www.epa.gov/chemical-data-reporting.

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
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  1. production associated with the non-TSCA use will not be reported to CDR. Use for sunscreens specifically is not reported via CDR but the broader category of personal care uses are reported. Information not considered confidential business information (CBI) is available publicly.
  2. European Chemicals Agency (ECHA) dossiers4: Manufacturers, importers, or their representatives must submit information related to identifying and managing risks for substances regulated by REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) in the European Union to ECHA. ECHA creates publicly available dossiers (fact sheets) containing information for each substance, including the total tonnage from all contributed registrations that are not identified as confidential. The actual product categories are given for each UV filter in greater detail than available in the United States; however, tonnage estimates are aggregated across all products in the public fact sheets.
  3. FDA Voluntary Cosmetic Reporting Program (VCRP)5 and National Drug Code Directory6: Sunscreens are regulated as both cosmetics and drugs by FDA, and thus will be subject to reporting requirements for both categories. The VCRP is a reporting system for use by manufacturers, packers, and distributors of cosmetic products to consumers in the United States. It does not apply to products for professional use (e.g., at salons, spas, skin care clinics). Cosmetic manufacturers, packers, or distributors file a statement for each product the firm has entered into commercial distribution in the United States. Because reporting is voluntary, product frequency can be used to assess relative use, but not total use, across UV filters. Additionally, there is no indication of the mass or percentage of UV filters in each product nor how many of the products are sunscreens. Given the nature of this data source, it is most useful as a screening measure in the absence of any tonnage information. In addition to the VCRP, FDA maintains the National Drug Code Directory, which lists UV filters under a drug use application along with its product and strength (g UV filter/100 g product). Information on market share is not present; therefore, the information does not help provide overall tonnages of UV filters.
  4. Market Research: Several market research companies compile and aggregate market data such as profits and production values and conduct market analysis to understand emerging consumer behavior patterns (use, preference, etc.) on individual substances or product categories (e.g., sunscreens). Sources that might include data about sunscreens or UV filters include Nielsen or the Chemical Economics Handbook. The data are available for a fee and with limited terms of use, but are otherwise available to anyone. The advantage of market data is they can be collected for specific product types (i.e., sunscreens), as opposed to data provided by UV filter manufacturers, which is more likely to be for unspecified or a broad range of uses. FDA conducted a market data analysis using their drug registration information, retail sales data for market data companies, and product information available on the internet as part of the regulatory impact analysis of the 2019 proposed sunscreen monograph (FDA, 2019).

Data from these four sources were provided to the committee by the Personal Care Product Council (PCPC), which had compiled these data for use in their own analysis described to the committee at a public meeting (see Burns et al., 2021; presentations to the committee by Iain Davies, May 27, 2021, and Emily Burns, May 28, 2021). Market data on personal care product usage in 2019 were purchased by PCPC from Euromonitor.7 A version of these data is in Appendix B and described in the following section.

UV Filters in Personal Care Products

The compounds used as UV filters in sunscreens are also used in other personal care products including makeup, shampoo and conditioner, hair dyes, body wash, and toothpaste (Keller et al., 2014; see Appendix B). UV filters from personal care products other than sunscreen formulations may be one of the hardest to distinguish as

___________________

4 See https://echa.europa.eu/information-on-chemicals/registered-substances.

5 See https://www.fda.gov/cosmetics/voluntary-cosmetic-registration-program.

6 See https://www.accessdata.fda.gov/scripts/cder/ndc/index.cfm.

7 See https://www.euromonitor.com/usa.

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×

a source in the aquatic environment from sunscreen because they are expected to have similar means of entering the environment and potential chemical fates (particularly for entry into municipal wastewater, though sunscreen may still outweigh other personal care products in beach rinse-off). Other uses of UV filters beyond personal care and cosmetics, such as in packaging or longer-lived applications (e.g., tires, paints, plastics) might be assumed to end up in landfills and other terrestrial compartments, though information is lacking.

According to EPA CDR, TiO2 (12,187 mt) and ZnO (5,843 mt) are leading compounds by total amount used in personal care products. Uses of organic UV filters are less than these inorganics, with homosalate being the UV filter most prevalent in personal care products (3,410.4 mt). Sunscreen is not distinguished from other personal care products in publicly available information from EPA CDR. But according to the market data shared with the committee, 90 percent of personal care products containing homosalate are for the purposes of sun care, compared to only 2 percent of personal care products containing TiO2 and 35 percent containing ZnO.

However, an analysis by Keller et al. (2014) based on estimates drawn from consumer surveys regarding product usage indicate that sunscreens may account for around 80 percent of personal care product usages for nano forms of TiO2 and ZnO. Keller et al. (2014) applied a series of modeling scenarios and estimates to bound low to high usage rates with predictions from market surveys. Numerical differences in tonnages between Keller et al. and other estimation methods can be accounted for by different limitations in estimation and survey methods although directionally (e.g., relative percent material flow for various uses) they may be similar.

In addition to homosalate, other UV filters that appear to be in regular use are octocrylene, octinoxate, octisalate, avobenzone, and the benzophenones. EPA CDR reports octocrylene production of 259 mt for personal care products, octinoxate at 84.2 mt, octisalate at 35.8 mt, and dioxybenzone at 23.5 mt. EPA CDR does not include data for avobenzone, nor data in the personal care product category for oxybenzone or sulisobenzone. However, according to market data from 2019, avobenzone is used an average of 8.2 mg/capita/day (approximately 982 mt total in the United States) in personal care products, 70 percent of this was sunscreen use. Euromonitor groups the benzophenones (dioxybenzone, oxybenzone, sulisobenzone) together, with a combined use of 11.4 mg/capita/day (1,355 mt total in the United States) in personal care products, about 82 percent for sunscreens. Similarly, about 80 percent of octocrylene and octisalate used in personal care product tonnages are for sunscreens. Octinoxate is lower, at 36 percent of personal care products containing the compound to be used in sunscreens.

The remainder of the organic UV filters are used in small or unknown amounts. Ensulizole is on the low spectrum of usage for personal care products, with no information from EPA CDR and, based on market data, an average of only 0.1 mg/capita/day (or about 12 metric tonnes in the United States) in sunscreens, representing 17 percent of its usage for personal care products. As expected, since they have been phased out of use as UV filters, no data source indicates that aminobenzoic acid or trolamine salicylate are currently in use in personal care products in the United States. ECHA data does identify aminobenzoic acid as an ingredient in personal care products in Europe but these data do not associate total volumes to individual uses, and the scale of overall use is low (in the reporting band of 1 to 10 mt). There are also no data to indicate whether or not meradimate, cinoxate, or padimate O are currently in common use in sunscreens or other personal care products, though EPA CDR indicates an annual production of about 80 tonnes of meradimate in 2015 for unspecified use. Lastly, ecamsule is in limited use in the United States. It is reported in the 100 to 1,000 mt reporting band for use in cosmetics and personal care products used in the European Union.

FDA’s analysis of sunscreen registration and sales data information can provide further insight into the use of UV filters in sunscreens specifically (FDA, 2019). FDA’s analysis estimated volumes of consumption based on the number of sunscreens containing each ingredient (based on drug registrations and online product information), average volumes, and sales of each product (based on data from Euromonitor and Information Resources, Incorporated). The volume estimates are limited by the assumptions that went into this extrapolation; however, they should be indicative of the relative usages of each UV filter in sunscreens. This analysis of data from 2016 identifies avobenzone, octisalate, octocrylene, homosalate, oxybenzone, octinoxate, TiO2, and ZnO as the most commonly used UV filters (see Table 2.2). Ensulizole, meradimate, padimate O, and sulisobenzone are used in relatively small amounts. Aminobenzoic acid, cinoxate, dioxybenzone, and trolamine salicylate are not found to be in use. The designations between frequently used and minimally/unused UV filters roughly align with what was found in the EPA CDR and/or Euromonitor data, though exact volumes may vary. Lack of information about

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×

TABLE 2.2 Prevalence of Currently Marketed UV Filters in Sunscreen Products

Estimated 2016 Consumption (millions of ounces)
Active Ingredient Productsa Lower Bounda Primary Estimatea Upper Bounda
Avobenzone 1,641 841.65 1,040.21 1,238.77
Octisalate 1,791 756.53 971.33 1,186.13
Octocrylene 1,432 807.36 1,001.79 1,196.22
Homosalate 1,167 741.79 873.67 1,005.55
Oxybenzone 1,342 728.70 821.11 913.52
Octicoxate 1,940 168.52 304.42 440.32
TiO2 1,427 114.49 173.71 232.93
ZnO 1,342 119.90 186.44 252.98
Ensulizole 88 5.58 25.61 45.64
Meradimate 20 2.63 14.10 25.58
Padimate O 31 11.16 11.47 11.79
Sulisobenzone 4 0.24 0.41 0.58
Aminobenzoic Acid (PABA) 0 0.00 0.00 0.00
Cinoxate 0 0.00 0.00 0.00
Dioxybenzone 0 0.00 0.00 0.00
Trolamine Salicylate 0 0.00 0.00 0.00

a If a product contains more than one active ingredient, then we include it in the number of products and the quantity consumed for all relevant rows. SOURCE: FDA, 2019.

avobenzone and oxybenzone in EPA CDR is likely due to reporting limitations, since these are indicated to be frequently used UV filters. This also suggests that oxybenzone is the dominant contributor to “benzophenone” usage data in Euromonitor, and EPA CDR data for dioxybenzone may apply to non-sunscreen personal care products.

Some general insights can be gained from these estimates. When looking at personal care products, most organic UV filters in regular use are predominantly, but not exclusively, used in sunscreens (octinoxate being the clearest exception). Comparatively, sunscreens are potentially a smaller proportion of the personal care product usage for inorganic UV filters. However, inorganic UV filters are used in much higher amounts in personal care products in general compared to organic UV filters. For the UV filters for which EPA CDR and Euromonitor both contain data, total tonnages used in personal care products differ but the same relative usage pattern across the highest used (homosalate, ZnO, TiO2), least/not used (ensulizole, cinoxate, meradimate, padimate O, aminobenzoic acid, and trolamine salicylate), and moderately used (all others) UV filters is apparent. Data are incomplete at least for avobenzone, dioxybenzone, oxybenzone, padimate O, and sulisobenzone due to incomplete reporting in EPA CDR and/or the market data obtained by the committee. However, filling this gap, market data analyzed by FDA confirms avobenzone and oxybenzone are commonly used UV filters.

UV Filter Usage in Consumer Products

According to ECHA and EPA CDR data, which both track a range of product categories beyond personal care, inorganic UV filters (ZnO and TiO2) are used in many consumer products and at high volumes. These uses include building/construction materials, agricultural products (e.g., fertilizers), adhesives/sealants, electrical products, metal products, and paints and coatings. Production volumes of inorganic UV filters significantly exceed those of the organic UV filters, with total tonnages of over 100,000 mt for ZnO and over 1,000,000 mt for TiO2 according to EPA CDR and the ECHA reporting bands.

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×

EPA CDR associates tonnage with its product categories and shows that use for personal care is a small percentage for the inorganic UV filters (< 1 percent of ZnO uses and < 2 percent of TiO2 uses). While specific to engineered nanomaterials, the Sankey diagram from Keller and Lazareva (2014) in Figure 2.5 illustrates the flux of industrially produced materials (including the inorganic UV filters) through products used in society, and their wash-off, disposal, or other end-of-life processes where they enter different environmental compartments.

As shown in Figure 2.5, different types of products are expected to be disposed of or released to different environmental compartments. Those most likely to end up in the water include personal care products and coatings, paints, and pigments. For the nanomaterials depicted in Figure 2.5, the wider variety of product types may also contribute, but to a smaller degree. In all cases, the compounds may or may not first be treated in a wastewater treatment plant when used in homes or cities, and there is no treatment afforded to sunscreen release scenarios within swimming areas where UV filters directly wash off into the water column.

Based on ECHA data, avobenzone, homosalate, octocrylene, octinoxate, and octisalate are registered in the 1,000 to 10,000 mt band. Oxybenzone, padimate O, ensulizole, and sulisobenzone are registered at 100 to 1,000 mt. Dioxybenzone is listed in the 1 to 10 mt band, and the remainder of UV filters used in the United States (cinoxate, meradimate, trolamine salicylate, and aminobenzoic acid) are not listed. Their uses include personal care and cosmetics, processing aids, heating/cooling systems, furniture, welding and soldering products, washing/cleaning products, polishes/waxes, air care products, pharmaceuticals, automotive acre, paints/coatings, biocides, building/construction material, and long-life products (e.g., packaging, toys, books, electronics, footwear, fabrics/textiles). The publicly accessible information does not specify how much is used for sunscreen/personal care or other products specifically.

Compared to ECHA, EPA CDR contains fewer categories of use for organic UV filters. While this would in part reflect differences in usages of these compounds between the United States and Europe, this is also likely due to a difference in reporting requirements. The EPA CDR minimum reporting tonnage is 11.33 mt (25,000 lbs) so small-scale manufacturers may not submit reported uses. Many of the organic UV filters reported total tonnages are well below 100 mt (meradimate, octisalate, octinoxate, octocrylene, and sulisobenzone). Some UV filters, such

Image
FIGURE 2.5 Estimated global mass flow of engineered nanomaterials (in metric tons per year) from production to disposal or release, considering high production and release estimates as of 2010. SOURCE: Reprinted with permission from Keller and Lazareva, 2014. Copyright 2014 American Chemical Society.
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×

as homosalate, which are used almost exclusively in personal care, have apparently more robust tonnages because the information is not confounded by other uses.

Organic UV filters are frequently used in long-lived materials such as plastics, paints and coatings, tires, and electronics supposedly to reduce adverse material effects associated with sun exposure. Most of these applications pose an unknown potential for introduction into aquatic systems. For example, fabrics with UV filters applied (i.e., fabric coatings, laundry detergents, etc.) and subsequently washed in the home have been demonstrated to shed fibers or coatings during household use, with resultant releases dispersed down the drain to receiving aquatic environments (Browne et al., 2011). Plastics break down into microplastics, potentially enhancing their bioavailability, but very little data is available on whether UV filters would leach from the plastic matrix. Micronized rubber from tires is considered an emerging area of environmental pollution research and a role of UV filters has yet to be explored (Halle et al., 2020).

Relative Usage Between Personal Care and Other Products

UV filters are used in a very wide range of industrial and consumer product applications. Inorganic UV filters specifically are used in an exceptionally wide range of applications, and use in personal care products may be small for inorganic UV filters according to EPA CDR data. Identifying the breakdown of usage between personal care products and other uses is difficult in many cases because ECHA data does not associate tonnages to different categories and EPA CDR data does not appear to include as many reporting categories for the organic UV filters. For cases like homosalate, with tonnage estimates from EPA CDR comparable to ECHA’s overall totals, it is likely that personal care product usage is dominant. In other cases, such as for octisalate, octinoxate, octocrylene, tonnages reported in EPA CDR are far below that in ECHA. However, comparison of total numbers between the two datasets is difficult since they represent different populations, so attributing this to incomplete reporting may or may not be correct. A notable distinction between the European Union and the United States is the availability of a larger number of active ingredients used in sunscreens in the European Union and different ingredients may be favored. On the opposite end, dioxybenzone and padimate O are not reported in personal care products at all in EPA CDR or ECHA. However, other cases are more ambiguous, such as for oxybenzone, avobenzone, ensulizole, and sulisobenzone, which are reported as used in personal care products by ECHA but not by EPA CDR. As noted earlier, distinguishing between use in sunscreens and other personal care products is difficult from the available data.

Precise estimates of tonnages across all UV filters for use as sunscreens are likely needed to perform high quality environmental risk assessments. In the absence of widespread environmental monitoring, these tonnage estimates give an indication of the potential level of a chemical in the environment. Once there is a general understanding, this can initiate environmental monitoring and inform expected detection levels. Further, understanding which of the UV filter usages, other than personal care, have potential to be released to the environment is poorly known. Even amongst personal care products, sunscreens may have more potential for direct wash-off into an aquatic environment than those products more likely to wash off “down the drain” to wastewater treatment. This precision will help with prospective exposure models as well as the development of management practices that appropriately control sources that may be deemed to be an environmental risk.

FINDINGS AND KNOWLEDGE GAPS

Based on the information reviewed in this chapter, the committee highlights the following areas as key findings from the information as well as gaps in knowledge pertinent to understanding the environmental risk and the human health benefits from UV filters.

Finding: UV filters are part of sunscreen formulations that consist of mixtures of active and inactive ingredients, which influences their effectiveness as sunscreens and may influence their environmental input rate, fate, and toxicity.

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×

Finding: The compounds used as UV filters are not used exclusively in products marketed as sunscreens. Many different products may contribute to the release and detection of UV filters in the environment.

Knowledge Gap: The diversity of surface coatings and non-uniform morphology of inorganic UV filters complicates grouping of these active ingredients into categories that could readily enable exposure risk assessments.

Knowledge Gap: More precision in production and use volumes of UV filters specific to their usage in sunscreens would improve ability to clarify the contribution of UV filters from sunscreens compared with other products as a source in the environment and subsequently develop targeted management strategies.

Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 21
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 22
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 23
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 24
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 25
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 26
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 27
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 28
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 29
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 30
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 31
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 32
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 33
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 34
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 35
Suggested Citation:"2 Introduction to Sunscreens and Their UV Filters." 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. doi: 10.17226/26381.
×
Page 36
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Regular use of sunscreens has been shown to reduce the risk of sunburn and skin cancer, and slow photoaging of skin. Sunscreens can rinse off into water where people are swimming or wading, and can also enter bodies of water through wastewater such as from bathing or showering. As a result, the ultraviolet (UV) filters - the active ingredients in sunscreens that reduce the amount of UV radiation on skin - have been detected in the water, sediment, and animal tissues in aquatic environments. Because the impact of these filters on aquatic ecosystems is not fully understood, assessment is needed to better understand their environmental impacts.

This report calls on the U.S. Environmental Protection Agency to conduct an ecological risk assessment of UV filters to characterize the possible risks to aquatic ecosystems and the species that live in them. EPA should focus on environments more likely to be exposed such as those with heavy recreational use, or where wastewater and urban runoff enter the water. The risk assessment should cover a broad range of species and biological effects and could consider potential interacting effects among UV filters and with other environmental stresses such as climate change. In addition, the report describes the role of sunscreens in preventing skin cancer and what is known about how human health could be affected by potential changes in usage. While the need for a risk assessment is urgent, research is needed to advance understanding of both risks to the environment from UV filters and impacts to human health from changing sunscreen availability and usage.

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