Introduction:

 On a hot sunny day, children are always told to put sunscreen on to ensure protection from the sun’s harmful ultraviolet (UV) rays. Although, sunscreen protects individuals from UV radiation, there is nothing protecting the individual from the products in sunscreen. Many widely used sunscreens contain numerous harmful chemicals, including a compound known as oxybenzone (OBZ) (Dellorto 2012). The chemical OBZ, also known as Benzophenone-3 is an organic compound which absorbs both UVA and UVB radiation, making it a “good” compound for sunscreen (Oxybenzone 2005). OBZ has strong intramolecular hydrogen-bonds, which allows for intramolecular proton transfers in an excited state (Li et al. 2016). For this reason, among others, OBZ has been deemed a photo-toxicant chemical thus meaning when exposed to light it causes exacerbation of any adverse effects of OBZ. This characteristic has now begun to raise concerns in not only humans who apply OBZ sunscreen, but also to animals and marine environments (Downs et al. 2016).  A risk assessment on OBZ will be completed by looking at its hazard in humans and marine biota, assessing the toxicity of OBZ, its environmental exposure issues and the overall risk involved by using sunscreen containing OBZ.

Environmental Risk Characterization:1) Hazard of Using Oxybenzone

 Oxybenzone has been shown to be systemically absorbed by bodies after being applied to the skin; absorbed OBZ and metabolites are excreted through breast milk and urine (Sarveiya et al. 2004). The absorption of OBZ is based on a ratio of body surface area to body weight; children have a larger body surface area to body weight ratio than adults and therefore may experience greater absorption of OBZ than adults (Gonzalez et al. 2006). In both humans and animals, OBZ has been shown to have an impact on endocrine systems. This could potentially have an affect on fertility in men, their sperm production and their overall reproductive function (Chen et al. 2013), and lead to a decrease in sperm quality, intersex and reproductive toxicity in some organisms found in both wastewater and marine environments (Li et al. 2016; Coronado et al. 2008). OBZ has found to impact coral in marine ecosystems as well as their biota. According to a study conducted by Downs et al. (2016), OBZ acts as a genotoxin for coral which leads to mutations by damaging the corals DNA. OBZ deforms planulae from their mobile state which in turns leads to the bleaching of coral. In addition, OBZ exposure into bodies of water has cause viral infections in some plankton (McCoshum et al. 2016). Due to the large quantities of OBZ that enter the water in form of sunscreen alone, approximately 10% of reefs are at risk of being exposed to OBZ globally (Downs et al. 2016). 

2.1) Toxicity Assessment of Oxybenzone in Humans

 Oxybenzone has different toxicity values depending on the organism in question. No toxicity testing has been done directly on humans, instead toxicity testing gets done on animals, and the results are then believed to hold true for humans. A current review conducted by Lim et al. (2017) indicated that in rats who were fed 1500mg/kg/d of OBZ showed to have dose-dependent estrogenic activity, however when a short term study was completed on humans by topically applying OBZ, there was no significant change in their thyroid function or reproductive hormones. The European Chemicals Agency (ECHA) conducted studies of OBZ on animals looking at both acute toxicity as well as repeated toxicity by many modes of transportation including oral, dermal and other (ECHA 2017). ECHA determined that for acute toxicity that: orally (rats) the LD50 was greater than 12800 mg/kg, dermally (rabbits) the LD50 was greater than 16000 mg/kg bw, and by the intraperitoneal route (mice) the LD50 was greater than 1600 mg/kg. In regards to repeated dose toxicity, ECHA (2017) determined that orally in mice, the NOAEL was 393 mg/kg bw/d for females and 429 mg/kg bw/d for males based on lesion that were found on kidneys. Dermally in both rats and mice ECHA (2017) determined that the NOAEL value in both species is 200 mg/kg bw/d. These LD50 and NOAEL values are deemed to be very high and therefore, according to Wang et al. (2011) the required amount of OBZ needed per unit of body mass for a human, is believed to be unattainably large for sunscreen before any minor side effects arise. However, Wang et al. (201l) state that there are some individuals who claim their skin has become irritated due to sunscreen containing OBZ It is uncertain if these irritations are from the OBZ alone, or if other chemicals also play a part. Therefore, at the moment, there are no human acute toxicity values for systemic absorption of OBZ.

2.2) Toxicity Assessment of Oxybenzone in the Marine Environment

 The chemical OBZ which enters marine ecosystems has been shown to cause feminization of male fish and reduction of sperm= at approximately 1mg/L and shown to cause stimulation of vitellogenin, (due to increased levels of estrogen), between 600-750 μg/L (Bratkovics et al. 2015).  A LD50 was not determined, however a study conducted by Danovaro et al. (2008), tested sunscreen contained OBZ and its effects on coral, and determined that even with a small amount of sunscreen (10μL/L) introduced to coral, bleaching occurred within 96 hours. According to Hopkins et al. (2017), OBZ can become genotoxic to coral and their planulae at concentration levels of 62ng/L. It has been concluded that OBZ has a IC10 value of 0.56 mg/L for growth inhibition in algae and a EC50 of 13.87 μg/L for algae. OBZ has an acute toxicity EC50 value of 1.67 mg/L in D. magna, a EC50 value of 3288 μg/L in sea urchin larvae and some crustaceans have shown to have a EC50 of 710.76 μg/L (Paredes et al. 2014; Sieratowicz et al. 2011).

3) Environmental exposure issues of oxybenzone

 In humans, OBZ exposure is based almost solely on exposure to skin (i.e. applying sunscreen). The chemical is absorbed through the skin and crosses the corneum strata of skin. It then enters the blood stream and circulates throughout the body and organs, eventually excreting via urine (Fediuk et al. 2012). OBZ is entering bodies of water in multiple ways including through direct input (washing off of skin) and watershed. OBZ enters aquatic environments primarily due to humans, and it washing off their skin or clothes while in the water. Another major source of OBZ release is by sewage sludge and effluents from wastewater treatments (Campos et al. 2017; Paredes et al. 2014). Coronado et al. (2008) determined that some wastewater has OBZ values lower than needed to significantly effect some species. They determined that wastewater around New York contained 19 ng/L of OBZ and in Swiss lakes discharge of OBZ only ranged from 2-35ng/L. Both these values are significantly less the what they determined what was needed to affect biota in those regions (620 ug/L). There is a larger risk in oceans where OBZ enters the environment in other ways, not only sunscreen. The main danger for OBZ in marine environments is that due to its chemical and physical properties which make it stable and lipophilic, causing it to remain in the environment over a long period of time (Li et al. 2016).

4) Overall Risk of Oxybenzone in the Environment

 The chemical OBZ, has been shown to bio-accumulate in the environment which could potentially lead to more severe adverse effects on the biota (Li et al. 2016), as well as affecting tropic levels which means OBZ can make its way up the food chain. Studies done on tropic levels in the marine ecosystem have shown that animals in different tropic levels have OBZ traces (McCoshum et al. 2016). The fact that OBZ is making its way up tropic levels, could mean that humans may begin ingesting OBZ through food sources. Studies by McCoshum et al. (2016) and Lim et al. (2017), have determined that OBZ and other sunscreen chemicals have been found in filter-feeding organisms and effecting photosynthetic organisms and their prey. Overall, OBZs could threaten reefs and organism world wide. Bleaching and death of corals, will impact all organisms around them, due to the loss of food and nutrients that some biota receive from coral. Companies have begun to manufacture organic sunscreen that do not contain OBZs to aid in reducing exposure of the chemical to the environment.

Conclusion:

 The compound OBZ is primarily located in sunscreen. It has been shown to cause disruptions in endocrine systems of animal which can lead to a reduction in sperm and fertility. In the marine environment OBZ has been known to effect large quantities of marine biota including: coral, fish, zooplankton and algae, which all have different toxicity values for that compound. Humans, animals, and marine biota are all being affected by OBZ one way or another whether it be a rash (humans), endocrine disruptions (animals and marine biota) or as severe as bleaching of coral or death in some organisms, something must be done. Some companies are reducing or eliminating OBZ from their sunscreen and products however, there is already so much OBZ in the environment. Although this is a start, science needs to determine how to eliminate the OBZ that has already made its way into bodies of water. Different countries have limited the amount of OBZ allowed in sunscreen and cosmetics; Australia, up to 10%, Canada, United States and the European Union allow up to 6% in sunscreen, less in cosmetics and Japan having a limit of 5%. However, Hawaii is in the midst of trying to ban OBZ to protect their reefs (Vesper 2017). More research needs to be done on OBZs toxicity in humans as well as research to rid marine environments from this chemical.

Cited References

Bratkovics S, Wirth E, Sapozhnikova Y, Pennington P, Sanger D. 2015. Baseline monitoring of organic sunscreen compounds along South Carolina’s coastal marine environment. Marine Pollution Bulletin 101:370-377.

Campos D, Gravato C, Quintaneiro C, Golovko O, Žlábek V, Soares A, Pestana J. 2017. Toxicity of organic UV-filters to the aquatic midge Chironomus riparius. Ecotoxicology and Environmental Safety 143:210-216.

Chen M, Tang R, Fu G, Xu B, Zhu P, Qiao S, Chen X, Xu B, Qin Y, Lu C et al. 2013. Association of exposure to phenols and idiopathic male infertility. Journal of Hazardous Materials 250-251:115-121.

Coronado M, De Haro H, Deng X, Rempel M, Lavado R, Schlenk D. 2008. Estrogenic activity and reproductive effects of the UV-filter oxybenzone (2-hydroxy-4-methoxyphenyl-methanone) in fish. Aquatic Toxicology 90:182-187.

Danovaro R, Bongiorni L, Corinaldesi C, Giovannelli D, Damiani E, Astolfi P, Greci L, Pusceddu A. 2008. Sunscreens Cause Coral Bleaching by Promoting Viral Infections. Environmental Health Perspectives 116:441-447.

Dellorto D. 2012. Avoid sunscreens with potentially harmful ingredients, group warns. CNN. [accessed 2017 Nov 19]. http://www.cnn.com/2012/05/16/health/sunscreen-report/index.html

Downs C, Kramarsky-Winter E, Segal R, Fauth J, Knutson S, Bronstein O, Ciner F, Jeger R, Lichtenfeld Y, Woodley C et al. 2016. Toxicopathological Effects of the Sunscreen UV Filter, Oxybenzone (Benzophenone-3), on Coral Planulae and Cultured Primary Cells and Its Environmental Contamination in Hawaii and the U.S. Virgin Islands. Archives of Environmental Contamination and Toxicology 70:265-288.

(ECHA) European Chemicals Agency. 2017. Oxybenzone. European Chemicals Agency. [accessed 2017 Nov 21]. https://echa.europa.eu/registration-dossier/-/registered-dossier/5515/7/3/5

Fediuk D, Wang T, Chen Y, Parkinson F, Namaka M, Simons K, Burczynski F, Gu X. 2012. Metabolic Disposition of the Insect Repellent DEET and the Sunscreen Oxybenzone Following Intravenous and Skin Administration in Rats. International Journal of Toxicology 31:467-476.

Gonzalez H, Farbrot A, Larko O, Wennberg A. 2006. Percutaneous absorption of the sunscreen benzophenone-3 after repeated whole-body applications, with and without ultraviolet irradiation. British Journal of Dermatology 154:337-340.

Hopkins Z, Snowberger S, Blaney L. 2017. Ozonation of the oxybenzone, octinoxate, and octocrylene UV-filters: Reaction kinetics, absorbance characteristics, and transformation products. Journal of Hazardous Materials 338:23-32.

Li C, Guo W, Xie B, Cui G. 2016. Photodynamics of oxybenzone sunscreen: Nonadiabatic dynamics simulations. The Journal of Chemical Physics 145:074308.

Li J, Ma L, Xu L. 2016. Transformation of benzophenone-type UV filters by chlorine: Kinetics, products identification and toxicity assessments. Journal of Hazardous Materials 311:263-272.

Lim H, Arellano-Mendoza M, Stengel F. 2017. Current challenges in photoprotection. Journal of the American Academy of Dermatology 76:S91-S99.

McCoshum S, Schlarb A, Baum K. 2016. Direct and indirect effects of sunscreen exposure for reef biota. Hydrobiologia 776:139-146.

Oxybenzone. 2005. Pubchem.ncbi.nlm.nih.gov. [accessed 2017 Nov 19]. https://pubchem.ncbi.nlm.nih.gov/compound/oxybenzone#section=Top

Paredes E, Perez S, Rodil R, Quintana J, Beiras R. 2014. Ecotoxicological evaluation of four UV filters using marine organisms from different trophic levels Isochrysis galbana, Mytilus galloprovincialis, Paracentrotus lividus, and Siriella armata. Chemosphere 104:44-50.

Sarveiya V, Templeton J, Benson H. 2004. Inclusion Complexation of the Sunscreen 2-Hydroxy-4-Methoxy Benzophenone (Oxybenzone) with Hydroxypropyl-?-Cyclodextrin: Effect on Membrane Diffusion. Journal of Inclusion Phenomena and Macrocyclic Chemistry 49:275-281.

Sieratowicz A, Kaiser D, Behr M, Oetken M, Oehlmann J. 2011. Acute and chronic toxicity of four frequently used UV filter substances forDesmodesmus subspicatusandDaphnia magna. Journal of Environmental Science and Health, Part A 46:1311-1319.

Vesper I. 2017 Mar. Hawaii seeks to ban reef-unfriendly sunscreen. Nature.

Wang S, Burnett M, Lim H. 2011. Safety of Oxybenzone: Putting Numbers Into Perspective. Archives of Dermatology 147:865-866.