UV Filter Restrictions Continue to Disrupt Sunscreen Innovation

Introduction

UV filters—the active ingredients in sunscreen products that absorb, reflect, or scatter ultraviolet radiation—remained subject to ongoing regulatory scrutiny during 2023, creating significant challenges for sunscreen innovation and product development [1]. Regulation (EC) No 1223/2009 classifies UV filters as a special category of cosmetic ingredients subject to authorization under Annex VI, requiring demonstration of safety and efficacy before approval [2]. The Scientific Committee on Consumer Safety (SCCS) evaluates UV filters through comprehensive safety assessments addressing dermal absorption, systemic toxicity, endocrine activity, and environmental impact, particularly effects on aquatic ecosystems [3]. By October 2023, several commonly used UV filters faced restrictions or prohibitions due to safety concerns, while new UV filter applications remained pending authorization, creating a supply constraint that limited formulation options and hindered development of broad-spectrum, high-SPF sunscreens [4].

The regulatory challenges surrounding UV filters exemplified the tension between public health objectives—preventing skin cancer and photoaging through effective sun protection—and precautionary regulation of ingredients with potential safety or environmental concerns [5]. Octocrylene, a widely used UV filter, faced scrutiny due to degradation to benzophenone, a suspected carcinogen and endocrine disruptor [6]. Benzophenone-3 (oxybenzone) and octinoxate faced restrictions in some jurisdictions due to concerns regarding coral reef toxicity, though these restrictions were not adopted EU-wide [7]. Titanium dioxide and zinc oxide nanoparticles, used in mineral sunscreens, remained subject to the Article 16 nanomaterial notification framework and ongoing SCCS review [8].

Regulatory Framework and Legal Analysis

Annex VI of Regulation (EC) No 1223/2009 lists UV filters permitted in cosmetic products, specifying maximum concentrations, authorized uses, and any required warnings or conditions [9]. Article 14(1)(a) prohibits the use of UV filters except those listed in Annex VI, creating a positive list system where only explicitly authorized substances may be used [10]. Article 31 establishes the procedure for amending Annex VI, requiring submission of an application dossier containing comprehensive safety and efficacy data, evaluation by the SCCS, and adoption of a Commission decision [11].

The application dossier for a new UV filter must include: (a) the identity and specification of the substance; (b) the function and proposed uses; (c) the proposed maximum concentration in finished products; (d) the toxicological profile, including dermal absorption, acute toxicity, irritation, sensitization, repeated-dose toxicity, mutagenicity, carcinogenicity, reproductive toxicity, and photo-induced toxicity; (e) the efficacy data demonstrating UV absorption properties; and (f) the reasonably foreseeable exposure [12]. The SCCS evaluates the dossier according to the Notes of Guidance (10th Revision, SCCS/1602/18) and issues an opinion on whether the substance can be safely used as a UV filter at the proposed concentration [13].

The SCCS assessment of UV filters emphasizes several critical endpoints. Dermal absorption is particularly important because UV filters are applied to large body surface areas at high concentrations (typically 2-10% for organic filters, up to 25% for inorganic filters), resulting in potentially significant systemic exposure [14]. The SCCS requires in vitro dermal absorption studies using validated methods (e.g., OECD TG 428) and, if significant absorption is observed, in vivo studies to confirm systemic bioavailability [15]. Systemic exposure dosage (SED) is calculated based on dermal absorption data and realistic use scenarios, including repeated application and use on children [16].

Endocrine activity is a key concern for several UV filters, as in vitro assays have demonstrated estrogenic, anti-androgenic, or thyroid-disrupting activity for substances such as benzophenone-3, octinoxate, and homosalate [17]. The SCCS evaluates endocrine activity using the weight-of-evidence approach, integrating in vitro mechanistic data, in vivo toxicity studies, and human exposure information [18]. If endocrine-mediated adverse effects are observed in repeated-dose or reproductive toxicity studies, the NOAEL for those effects is used to calculate the margin of safety, and an MoS ≥100 is required [19].

Photo-induced toxicity is unique to UV filters because these substances are designed to absorb UV radiation and may undergo photochemical reactions generating reactive oxygen species or photoproducts with altered toxicity [20]. The SCCS requires photo-irritation and photo-sensitization testing, typically using in vitro methods such as the 3T3 Neutral Red Uptake Phototoxicity Test (3T3 NRU PT) [21]. If positive results are obtained, in vivo photo-patch testing may be required to assess clinical relevance [22].

Environmental impact, particularly aquatic toxicity, has become an increasingly important consideration in UV filter assessment [23]. Several studies have demonstrated that organic UV filters, particularly benzophenone-3 and octinoxate, cause coral bleaching and disrupt coral reproduction at environmentally relevant concentrations [24]. While Regulation (EC) No 1223/2009 does not formally require environmental risk assessment for cosmetic ingredients, the SCCS has begun to consider environmental data in its opinions, and some Member States have advocated for incorporation of environmental criteria into the authorization process [25].

By October 2023, several UV filters faced regulatory challenges. Octocrylene (Annex VI entry 22) remained authorized at concentrations up to 10%, but concerns regarding degradation to benzophenone prompted calls for re-evaluation [26]. Benzophenone-3 (Annex VI entry 3) remained authorized at concentrations up to 6% in the EU, despite restrictions in Hawaii, Palau, and other jurisdictions due to coral reef concerns [27]. Homosalate (Annex VI entry 15) was under SCCS review due to endocrine activity and potential for bioaccumulation [28]. Several new UV filter applications, including bemotrizinol and iscotrizinol, remained pending SCCS evaluation, delaying their market availability [29].

Toxicological and Safety Science Considerations

The toxicological assessment of UV filters requires integration of dermal absorption, systemic toxicity, endocrine activity, and photo-induced toxicity data [30]. Dermal absorption studies demonstrate that organic UV filters, which are typically lipophilic molecules with molecular weights of 200-400 Da, can achieve significant dermal penetration [31]. For example, benzophenone-3 demonstrates dermal absorption of approximately 1-2% in in vitro studies, but biomonitoring studies have detected the compound in urine, blood, and breast milk of the majority of the population, suggesting that actual absorption may be higher [32]. Octocrylene demonstrates lower dermal absorption (<1%), but its widespread use and high application concentrations result in measurable systemic exposure [33].

Systemic exposure dosage (SED) calculation for UV filters must account for realistic use scenarios, including application to large body surface areas (e.g., whole body for beach use), repeated application (every 2 hours as recommended), and use by vulnerable populations (children, pregnant women) [34]. The SCCS typically assumes a whole-body application amount of 2 mg/cm², applied twice daily, resulting in a total daily application of approximately 36 g for an adult [35]. For a UV filter used at 10% concentration with 1% dermal absorption, this yields a SED of approximately 0.06 mg/kg bw/day for a 60 kg adult [36].

Margin of safety (MoS) calculation compares the SED to the NOAEL derived from the most sensitive relevant endpoint in repeated-dose or reproductive toxicity studies [37]. For UV filters, the SCCS typically requires an MoS ≥100, accounting for interspecies extrapolation (10-fold) and intraspecies variability (10-fold) [38]. If endocrine-mediated effects are observed, the NOAEL for those effects is used, and the SCCS may require a higher MoS (e.g., ≥200) to account for uncertainty regarding low-dose effects and mixture toxicity [39].

Endocrine activity of UV filters has been extensively studied using in vitro assays such as estrogen receptor (ER) binding assays, androgen receptor (AR) antagonist assays, and steroidogenesis assays [40]. Benzophenone-3 demonstrates estrogenic activity in vitro, with EC50 values in the micromolar range, indicating weak potency compared to endogenous estrogens [41]. However, in vivo studies in rodents have demonstrated effects on reproductive organ weights and pubertal development at doses resulting in systemic exposure comparable to human exposure from sunscreen use [42]. The SCCS concluded that benzophenone-3 is safe at concentrations up to 6% based on the overall weight of evidence, but recommended continued monitoring of biomonitoring data and epidemiological studies [43].

Octocrylene degradation to benzophenone is a particular concern because benzophenone is classified as a suspected carcinogen (Category 2) and demonstrates endocrine activity [44]. Studies have demonstrated that octocrylene in sunscreen formulations degrades over time, particularly when exposed to heat and light, generating benzophenone at concentrations that may exceed 1% after one year of storage [45]. The SCCS has not yet issued a formal opinion on octocrylene degradation, but the issue has prompted calls for re-evaluation and potential restriction [46].

Titanium dioxide and zinc oxide nanoparticles, used in mineral sunscreens, present unique toxicological considerations due to their particulate nature [47]. Dermal absorption studies demonstrate that these nanoparticles remain largely confined to the stratum corneum and do not penetrate to viable epidermis or achieve systemic absorption [48]. However, inhalation exposure from spray sunscreens is a concern, as nanoparticles can reach the deep lung and cause pulmonary inflammation [49]. The SCCS has concluded that titanium dioxide and zinc oxide nanoparticles are safe for use in sunscreens at concentrations up to 25%, provided they are not used in spray applications that may lead to inhalation exposure [50].

Practical Compliance Guidance

For Responsible Persons developing sunscreen products, navigating UV filter restrictions requires strategic formulation planning, comprehensive safety assessment, and proactive monitoring of regulatory developments. First, formulation strategies should prioritize use of UV filters with robust safety profiles and stable regulatory status [51]. Avobenzone, octinoxate, octisalate, and homosalate remain widely used organic filters, though each has specific limitations (e.g., avobenzone photostability, octinoxate endocrine concerns, homosalate under review) [52]. Inorganic filters (titanium dioxide and zinc oxide nanoparticles) provide broad-spectrum protection and favorable safety profiles, but may present aesthetic challenges (white cast) and require careful formulation to ensure dispersion stability [53].

Second, safety assessment under Article 10 must address all SCCS-required endpoints for UV filters, including dermal absorption, systemic toxicity, endocrine activity, and photo-induced toxicity [54]. Part A of the CPSR should include comprehensive toxicological data for each UV filter, including in vitro and in vivo studies, and Part B should calculate SED and MoS for each filter and for the combination of filters in the formulation [55]. If multiple UV filters are used, the CPSR should address potential mixture effects, considering whether filters act on the same toxicological pathways (e.g., multiple filters with endocrine activity) [56].

Third, stability testing is critical to ensure that UV filters do not degrade during product shelf life, generating photoproducts or degradation products with altered safety profiles [57]. For octocrylene-containing products, stability studies should specifically assess benzophenone formation, and if benzophenone concentrations exceed acceptable levels, reformulation or reduced shelf life may be necessary [58]. Article 11 requires that the PIF contain stability data, and Article 19 requires that the date of minimum durability or period after opening (PAO) be indicated on labelling [59].

Fourth, efficacy testing is required to substantiate SPF (Sun Protection Factor) and UVA protection claims [60]. ISO 24444:2019 specifies the in vivo method for SPF determination, and ISO 24442:2022 specifies the in vivo method for UVA protection factor (UVA-PF) determination [61]. The EU Recommendation on the efficacy of sunscreen products (2006/647/EC) recommends that sunscreen products provide both UVB protection (SPF ≥6) and UVA protection (UVA-PF ≥1/3 of SPF), and that products be labeled with the UVA logo if this criterion is met [62]. Claims substantiation under Article 20 and Commission Regulation (EU) No 655/2013 requires that SPF and UVA protection claims be supported by testing according to these standards [63].

Fifth, CPNP notification under Article 13 must identify all UV filters present in the formulation, and Article 19 labelling must list UV filters in the ingredient list using INCI nomenclature [64]. For products containing nanomaterials (e.g., titanium dioxide nanoparticles), Article 16 notification must be submitted six months prior to market placement, and Article 19 requires that “nano” be indicated in brackets following the ingredient name [65].

Sixth, Responsible Persons should monitor SCCS opinions and regulatory developments regarding UV filters, including pending applications for new filters and re-evaluations of existing filters [66]. Industry associations such as Cosmetics Europe provide updates on UV filter regulatory status and coordinate industry responses to SCCS consultations [67]. Early identification of potential restrictions enables proactive reformulation and reduces market disruption [68].

Conclusion

UV filter restrictions during 2023 continued to disrupt sunscreen innovation, as safety concerns regarding endocrine activity, degradation products, and environmental impact limited the availability of authorized filters and delayed approval of new alternatives. The positive list system established by Annex VI of Regulation (EC) No 1223/2009 ensures that only comprehensively evaluated UV filters are permitted, but the rigorous SCCS assessment process and evolving safety standards create supply constraints that challenge formulation flexibility. Responsible Persons must navigate this complex landscape through strategic formulation planning, comprehensive safety assessment, robust stability testing, and proactive monitoring of regulatory developments. As public health objectives regarding sun protection intersect with precautionary regulation of ingredients with potential safety or environmental concerns, the cosmetic industry must balance innovation with adherence to the science-based regulatory framework that protects both human health and the environment.

References

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