# A Survey of UV Filters Used in Sunscreen Cosmetics
## 3 Discussion
Both studies had similar prevalence values for other popular filters, i.e., ethylhexyl salicate (EHS) and ethylhexyl tiazone (EHT). In addition, similar values were noted for titanium dioxide (non-nano form) in child formulas in the Portuguese study (35.4%) and the presentstudy (28.0%). Interestingly, the benzophenone derivative DHHB, present in our study in preparations for adults and children with a share of as much as 38%, had, in the Portuguese study, a lower share by approximately 18 p.p. and 13 p.p. [34]. The availability of UV filters varies over time and undoubtedly depends on market forces and legal regulations. A 2014 survey of sunscreen products in the UK (n = 337) found the most common UV filters to be butyl methoxydibenzoylmethane (BMBM) and octocylene (OC), which were present in 96.4% and 90.5% of sunscreen products. Bis-ethylhexyloxyphenylenol methoxyphenyl triazine (BEMT) was found in 58.5% of products. Ethlyhexyl salicate (EHT), diethylhexyl butamido triazone, and methylene bis-benzotriazolyl tetramethylbutylphenol were found in around 32% each [35]. In the present study, the most frequently used UVA filter in adult sunscreens was butyl methoxydibenzoylmethane (BMBM; Avobenzene) (56.0%). Its frequency of use in child preparations was 36.0%, putting it in fifth position. Avobenzene is considered one of the most common allergenic and photoallergenic [36], and highly photolabile, UV filters [37]. Photopatch testing has found the reactivity rate of avobenzene to be 1.3-1.7% [38, 39]. It loses between 50% and 60% of its protective efficacy after one hour of exposure to UV radiation [40]. Avobenzene undergoes keto-enol tautomerism, and its keto form can easily photodegrade into 4-tert-butyl benzoic acid and 4-methoxy benzoic acid, which are responsible for its photoallergic and phototoxic reactions [11, 41]. Photodegradation of unstable UV filters such as avobenzene can be prevented by the use of photostabilizers, encapsulation, antioxidants, and the application of quenchers [42]. In addition, combining avobenzene with other photostable filters such as octocylene and Tinosorb S can also prevent photodegradation [43, 44]. Its photostability can also be improved by loading in cyclodextrin, e.g., beta-cyclodextrintrim polymers (pbCD) cross-linked by epichlorohydrin (pbCDE), or liposome lipid nanoparticles, microparticles, and polymeric nanoparticles [42, 45]. A test of avobenzene and five other organic filters (octisalate, homosalate, octocylene, oxycbenzene, octivacate) using the ToxCast/Tox21 database found all apart from oxycbenzene to have low intrinsic biological activity and a low risk of toxicity, including endocrine disruption, in humans [46]. In the present study, bis-ethylhexyloxyphenyl methoxyphenyl triazine (BEMT; Tinosorb S) was the most frequently used UV filter (60.0%) for children and the second most common (54.7%) for adults. Unlike avobenzene, BEMT is photostable. It is a broad absorption spectrum filter (UVB, UVA1, and UVA2) with minimal skin penetration and does not disrupt the functioning of the endocrine system [47, 48]. In 1999, SCCS confirmed that there was no evidence that this compound was toxic or allergenic [49]. Ethylhexyl salicate (EHS) was found to be one of the most popular UV filters in adult and child sunscreens, used in 54.7% and 46.0% of the studied samples. It demonstrates photodegradation and can induce some environmental toxicity [19, 34]. Clinical trial data indicates that it is systemically absorbed, resulting in plasma concentrations higher than the FDA systemic exposure threshold (0.5 ng/mL) [50]. Two cinnamic acid derivatives, octocylene (OC) and ethylhexyl methoxycinnamate (EHMC), were also quite popular UV filters in the present study. They were present in 36.6% (OC) and 24.0% (EHMC) of adult preparations, and 24.0% (OC) and 10.0% (EHMC) of child preparations. Unlike EHMC, octocylene does not exhibit any endocrine disruption potential nor is it photodegradable [19, 20]. OC rarely causes skin irritation reactions (0.6% for n = 1031 [20].