Degradation of Organic UV filters in Chlorinated Seawater Swimming Pools: Transformation Pathways and Bromoform Formation

Abstract

Organic ultraviolet (UV) filters are used in sunscreens and other personal-care products to protect against harmful effects of exposure to UV solar radiation. Little is known about the fate of UV filters in seawater swimming pools disinfected with chlorine. The present study investigated the occurrence and fate of five commonly used organic UV filters, namely dioxybenzone, oxybenzone, avobenzone, 2-ethylhexyl-4-methoxycinnamate, and octocrylene, in chlorinated seawater swimming pools. Pool samples were collected to monitor the variation of UV filter concentrations during pool opening hours. Furthermore, laboratory-controlled chlorination experiments were conducted in seawater spiked with UV filters to investigate the reactivity of UV filters. Extracts of chlorination reaction samples were analyzed using high-resolution mass spectrometry and electron-capture detection to identify the potentially formed byproducts. In the collected pool samples, all the UV filters except dioxybenzone were detected. Chlorination reactions showed that only octocrylene was stable in chlorinated seawater. The four reactive UV filters generated brominated transformation products and disinfection byproducts. This formation of brominated products resulted from reactions between the reactive UV filters and bromine, which is formed rapidly when chlorine is added to seawater. Based on the identified byproducts, the transformation pathways of the reactive UV filters were proposed for the first time.Bromoform was generated by all the reactive UV filters at different yields. Bromal hydrate was also detected as one of the byproducts generated by oxybenzone and dioxybenzone.

Development of transient mutagenic activity following the chlorination of the sunscreen UV filter dioxybenzone (benzophenone-8) in bromide-rich water

“…Therefore, the observed genotoxicity can be considered unrelated to volatile or semi-volatile DBPs, but rather a result of the formation of non-volatile transformation products. Besides, DBPs and specifically bromoform has been shown to be a common byproduct formed from all the UV filters studied here following chlorination in seawater (Manasfi et al 2017a). However, since mutagenicity in chlorinated seawater was only detected in the case of DIOXY, this further suggests that the observed mutagenicity is not related to the volatile DBP (ones forms by all the studied UV filters) but wa rather related to intermediate non-volatile products specific to the UV filter in question.…”

“…Optimum ESI conditions were found using a 2.5 kV capillary voltage, 30 V sample cone voltage, 450 °C desolvation temperature, 120 °C source temperature, 20 L/h cone gas flow rate and 800 L/h desolvation gas flow rate. The optimum sample cone voltage for each UV filter has been described previously (Manasfi et al, 2017a).…”

“…Analysis was performed in non-target screening and suspect screening modes. Suspect screening was performed based on previously identified transformation products of DIOXY (Manasfi et al, 2017a). In the mutagenic sample, five brominated transformation products namely Dioxy-Br, Dioxy-Br2, Dioxy-Br3, 3,5-dibromosalicylic acid, and TBMP were detected ( Table 2).…”

“…The chlorination of organic UV filters has been shown to result in the production of compound-specific transformation products as well as non-compound-specific DBPs such as chloroform and bromoform (Negreira et al, 2008;Duirk et al, 2013;Manasfi et al, 2015;Manasfi et al, 2017a). Some of the formed volatile and semi-volatile DBPs have been shown to be genotoxic (Richardson et al 2008;Zhang el al., 2016;Manasfi et al 2017b).…”

“…Furthermore, the reaction of UV filters with chlorine added for disinfection of swimming pool water or in wastewater treatment plants has received the attention of researchers since several years. In these studies, halogenated transformation products and disinfection byproducts have been identified for several organic UV filters (Santos et al, 2012;Duirk et al 2013;Sakkas et al 2003 ;Negreira et al 2008 ;Manasfi et al, 2015Kalister et al, 2016;Manasfi et al, 2017a). Despite evidence of transformation and formation of byproducts, there have been very few studies investigating the toxicity of the formed transformation products.…”