Why It Matters
Whether heading to the beach, the pool, or for an afternoon stroll, sunscreen is a prevalent component of many peoples’ lives. In recent years, the active ingredients in sunscreens have gained national attention for their negative impacts on aquatic life and associated human health concerns. A common active ingredient that has garnered attention is avobenzone - a widely used chemical UV filter, with the potential to form chemical by-products in the presence of UV-irradiation or chlorine in swimming pools. Avobenzone has exhibited adverse health effects in aquatic life and human metabolic function.
Understanding how chemical UV filters, like avobenzone, play a role in sunscreen formulations is crucial to finding the right product for optimal UV protection without sacrificing human and environmental safety.
What Is It?
Avobenzone is a common sunscreen ingredient. It offers broad-range UV coverage and blocks UVAI, UVAII, and UVB wavelengths when applied topically to the skin. It is most notably used for its ability to effectively filter long-wave UVA and is typically paired with other chemical UVB filters. In some countries, avobenzone is the only UVA filter available and is therefore widely used.
Where It's Found
Although a primary ingredient in sunscreens, avobenzone can also be found in other personal care products, cosmetics, and fragrance for its ability to stabilize products by delaying photodegradation and extending shelf life. Avobenzone and other organic UV filters may be added to industrial products like plastics, detergents, food packaging, or insecticides, amongst other uses.
The Health Concern
It is widely known that avobenzone is not photostable; when used without a stabilizing ingredient, UV light can break down avobenzone, rendering it an ineffective sunscreen. Typical choices for stabilizing ingredients used alongside avobenzone include octocrylene, homosalate, or octisalate, adding to the toxic cocktail of chemicals found in conventional sunscreen formulations. The breakdown of avobenzone can also cause the generation of free radicals within the skin. Free radicals can lead to oxidative damage and lipid peroxidation, which can lead to damage of lipids, DNA, and the cell overall.
Due to insufficient data, the US Food and Drug Administration (FDA) does not grant avobenzone a positive Generally Recognized As Safe and Effective (GRASE) determination. Avobenzone was placed on the TEDX list of Potential Endocrine Disruptors in 2015 and is an established endocrine disruptor.  A recent study published in 2019 showed evidence that avobenzone is a metabolic disrupting obesogen (compounds that may predispose humans to weight gain). There is additional evidence to suggest avobenzone disrupts homeostasis of skin barrier development, which could potentially promote the penetration of other chemicals through human skin; however, more research into this topic is necessary.
Avobenzone, amongst other chemical UV filters, shows evidence of toxicity and potential bioaccumulation in aquatic environments. Significant amounts of the substance have been detected in aquatic environments from wastewater effluent, landfills, or recreational activities.
When combined with chlorine and UV-irradiation, avobenzone forms other compounds as transformation products, which could potentially be even more toxic than the avobenzone, itself. A study published in 2016 found twenty-five by-products of avobenzone in the presence of chlorine and UV-irradiation (both as methods of disinfection in swimming pools), although most of their toxicity profiles are unknown. Inorganic salts in seawater can also react with avobenzone to form disinfection byproducts. The photolysis alone of avobenzone creates various by-products of unknown toxicity and persistence in aquatic environments. Existing literature on the aquatic toxicity of avobenzone fails to examine these by-products.
How to Avoid It
Read labels and avoid avobenzone. Avobenzone will often be listed as the active ingredient on sunscreen labels. Also, when shopping for sunscreen, seek out products with non-nano zinc oxide or titanium dioxide as the active UV filter(s). Finally, shop MADE SAFE Certified products.
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 Boyd, A., Stewart, C.B., Philibert, D.A., How, Z.T., El-Din, M.G., Tierney, K.B., Blewett, T.A. (2021). A burning issue: The effect of organic ultraviolet filter exposure on the behaviour and physiology of Daphnia magna. Science of the Total Environment. 750: 141707.
 Carve, M., Nugegoda, D., Allinson, G., Shimeta, J. (2020). A systematic review and ecological risk assessment for organic ultraviolet filters in aquatic environments. Environmental Pollution. 268: 115894.
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 Gagné, F. (2014). Chapter 6 – oxidative stress. In F. Gagné (Ed.), Biochemical ecotoxicology (pp. 103-115). Oxford: Academic Press.
 Ka, Y. and Ji, K. (2022). Waterborne exposure to avobenzone and octinoxate induces thyroid endocrine disruption in wild-type and thrαa−/− zebrafish larvae. Ecotoxicology. 31: 948-955.
 Lebedev, A.T., Kralj, M.B., Polyakova, O.V., Detenchuk, E.A., Pokryshkin, S.A., Trebse, P. (2020). Identification of avobenzone by-products formed by various disinfectants in different types of swimming pool waters. Environment International. 137: 105495.
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 TEDX List of Potential Endocrine Disruptors. (2015). Avobenzone.
 Trebse, P., Polyakova, O.V., Baranova, M., Kralj, M.B., Dolenc, D., Sarakha, M., Kutin, A., and Lebedev, A.T. (2016). Transformation of avobenzone in conditions of aquatic chlorination and UV-irradiation. Water Research. 101: 95-102.
 Yang, C., Lim, W., Bazer, F.W., Song, G. (2018). Avobenzone suppresses proliferative activity of human trophoblast cells and induces apoptosis mediated by mitochondrial disruption. Reproductive Toxicology. 81: 50-57.
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