A novel approach for unveiling co-occurrence patterns of UV filter mixtures in sunscreens: Prioritization for hazard and risk assessment

In recent years, concerns regarding the toxicity of organic UV filters in sunscreen products have increased. While sunscreen products contain multiple UV filters in combination, current understanding on their co-occurrence patterns and mixture toxicities is still limited. This study utilized a public database, "Hwahae", and analyzed 2183 sunscreen products marketed in South Korea as of 2019, using an association rule mining (ARM) to elucidate their co-occurrence patterns. We identified twenty-two UV filters in the sunscreen products, with titanium dioxide (TiO₂) being the most prevalent (68 %), followed by ethylhexyl methoxycinnamate (EHMC, 60 %) and ethylhexyl salicylate (EHS, 49 %). Sunscreen products typically contained a median of five UV filters per product. Usage patterns of UV filter mixtures varied by the target user group of the product, i.e., general, susceptible, and male users. EHMC and EHS were commonly combined in most products, except those marketed for susceptible users. For susceptible users, inorganic UV filters such as TiO₂ and zinc oxide (ZnO) were dominantly used. Combinations of UV filters that provide protection against different types of UV light, e.g., butyl methoxydibenzoylmethane (BMDBM) for UVA, and octocrylene (OCT), EHS, or homosalate (HS) for UVB, were also frequently used together, with high lift values. In conclusion, our study demonstrated that ARM approach can be useful to identify major combinations of UV filters present in sunscreen products, and prioritize the UV filter combinations requiring safety assessment and regulatory attention.