Degradation Products of Benzophenone-3 in Chlorinated Seawater

Article pubs.acs.org/est

Degradation Products of Benzophenone‑3 in Chlorinated Seawater Swimming Pools Tarek Manasfi, Veronika Storck,† Sylvain Ravier, Carine Demelas, Bruno Coulomb, and Jean-Luc Boudenne* Aix Marseille Université, CNRS, LCE FRE 3416, 13331 Marseille, France S Supporting Information *

ABSTRACT: Oxybenzone (2-hydroxy-4-methoxyphenone, benzophenone-3) is one of the UV filters commonly found in sunscreens. Its presence in swimming pools and its reactivity with chlorine has already been demonstrated but never in seawater swimming pools. In these pools, chlorine added for disinfection results in the formation of bromine, due to the high levels of bromide in seawater, and leads to the formation of brominated disinfection byproducts, known to be more toxic than chlorinated ones. Therefore, it seems important to determine the transformation products of oxybenzone in chlorinated seawater swimming pools; especially that users of seawater swimming pools may apply sunscreens and other personal-care products containing oxybenzone before going to pools. This leads to the introduction of oxybenzone to pools, where it reacts with bromine. For this purpose, the reactivity of oxybenzone has been examined as a function of chlorine dose and temperature in artificial seawater to assess its potential to produce trihalomethanes and to determine the byproducts generated following chlorination. Increasing doses of chlorine and increasing temperatures enhanced the formation of bromoform. Experiments carried out with excess doses of chlorine resulted in the degradation of oxybenzone and allowed the determination of the degradation mechanisms leading to the formation of bromoform. In total, ten transformation products were identified, based on which the transformation pathway was proposed.

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sunscreen formulations,13 together with octylmethoxycinnamate, butylmethoxydibenzoylmethane, octylsalicylate, and homosalate,2,3 since no single UV filter provides a sufficiently high sun-protection factor.14 BP-3 possesses physicochemical properties that explain its occurrence in various media. It is photochemically stable15 and lipophilic (octanol/water partition coefficient, log KOW = 3.8; pKa = 7.56)16 and thus has the ability to accumulate in fish,17 sediments,18 sewage sludges,19 and in soils.20 Although BP-3 is difficult to break-down in natural environments, it degrades upon chlorination leading to the formation of chlorinated byproducts that can be more toxic than their parent compounds.21,22 As a result, some attention has been paid in the last years to the fate of BP-3 in chlorinated waters,10,23 and especially in swimming pools where high levels of free chlorine are maintained for disinfection purposes. The upperlimit guidelines for free chlorine, expressed in Cl2, vary largely from one country to another (for example up to 5 mg/L in USA, as recommended by the National Swimming Pool Foundation (NSPF, 2010),24 to 1.4 mg/L in France,25 and to 0.6 mg/L in Germany).26 World Health Organization (WHO) recommends a concentration of free chlorine maintained at 1−3 mg/L in

INTRODUCTION Personal-care products (PCPs) belong to emergent organic compounds that are turning out to be a sticking point for both environmental and health concerns. Sunscreens and other PCPs such as shampoos, cosmetic creams, and hair sprays may contain UV filters added to protect against solar radiation.1 These filters are used in increasing quantities around the world and are now found in various environmental media.2 These compounds enter the environment either by direct inputs from bathing recreational activities (in seawater, lakes, rivers, and swimming pools) or by indirect inputs through sewage treatment plants. Their occurrences are reported in varying levels depending on sample location and intensity of recreational activities3 and ranged from low ng/L levels in surface waters4,5 to higher μg/L levels in swimming pools, bathing water, and wastewater.6 UV filters are considered as environmental contaminants of increasing concern since endocrine disrupting potentials have been emphasized for certain compounds.7,8 Other adverse effects on reproduction and fertility have also been detected in rodents and fish.9 There are about 55 UV filters approved for use in sunscreen products worldwide,10,11 but in Europe, since July 2013, only 28 molecules are authorized to be used on the EU market and may be present in ready-to-use sunscreens formulations at levels between 2 and 25%.12 Benzophenone-3 (2-hydroxy-4-methoxyphenone, also known as oxybenzone, BP-3) belongs to this short-list and represents one of largely used UV filters in © 2015 American Chemical Society

Received: Revised: Accepted: Published: 9308

February 15, 2015 July 6, 2015 July 13, 2015 July 13, 2015 DOI: 10.1021/acs.est.5b00841 Environ. Sci. Technol. 2015, 49, 9308−9316

Article

Environmental Science & Technology

potential risks associated with the presence of UV filters in swimming pools requires the evaluation of their degradation rates and their formed byproducts. For this purpose, the reactivity of BP-3 has been assessed as a function of chlorine dose and temperature in artificial seawater. The use of artificial seawater would allow the determination of the DBPs formed from the studied UV filter acting as a precursor without the interference of other organic compounds possibly present in real pool water and which would react with the added chlorine. The aims of the study were (i) to assess the THM formation potential of BP-3 in chlorinated seawater, (ii) to determine the nature of byproducts formed during chlorination and the chemical pathway leading to the formation of bromoform (CHBr3), and (iii) to determine the reactivity of the transformation products with chlorine in seawater. Experiments were carried out with aliquots of artificial seawater spiked with BP-3 (initial concentration of 100 μg/L) to which different doses of chlorine were added. Reactions were conducted at temperatures ranging from 25 to 35 °C. Ultraperformance liquid chromatography coupled with electrospray ionization mass spectrometry (UPLC-ESI-MS), gas chromatography coupled with mass spectrometry (GC-MS), and gas chromatography coupled with electron capture detection (GC-ECD) were employed for the identification and quantification of the generated byproducts.

swimming pools and 2−5 mg/L in hot spas.27 In such environments, chlorine reacts with organic compounds present in human body fluids (urine, sweat, hair, skin)28 and PCPs brought by swimmers to form disinfection byproducts (DBPs). Poiger et al.29 has estimated up to 1263 mg of UV filters are applied per person daily, but the reported instantaneous levels of BP-3 found in swimming pools and in shower wastewaters ranged from 2 to 10 μg/L.30,31 These apparent discrepancies (between daily inputs and amounts found) may be explained by the high reactivity of chlorine toward organic substances32 and more particularly for species with phenolic groups in their structures33,34 such as BP-3. This assertion is also supported by previous studies showing high reactivity of BP-3 with chlorine,21,23 with half-lives ranging from 0.8 to 2.8 min at pH varying from 7.2 to 8.2. However, according to our knowledge, there are no studies on the reactivity of BP-3 in chlorinated bromide-rich water (type of matrix found in seawater swimming pools), although evidence suggests that brominated disinfection byproducts (DBPs) are generally more toxic than their chlorinated analogues.35−38 In bromide-rich waters, disinfection with chlorine leads to the formation of brominated DBPs as hypochlorite ions (OCl−) and hypochlorous acid (HOCl) are rapidly converted to the more reactive oxidizing agents hypobromite ions (OBr − ) and hypobromous acid (HOBr);39,40 with this latter having an apparent second-order rate constant ranging between 103 and 105 M−1 s−1 toward phenolic groups at a neutral pH.34 The mechanism of reaction between HOBr and aromatic compounds involves electrophilic substitutions caused by the positive partial charge (δ+) of bromine in HOBr.41 Bromination occurs at the ortho or para positions of aromatic rings containing an activating group, with approximately 2/3 ortho substitution and 1/3 para substitution as suggested by the statistical distribution if these sites are unoccupied and no steric hindrance effects are present around.42 When all the ortho and para positions have been substituted, further bromination leads to ring opening and formation of trihalomethanes (THM).41,42,32 Negreira et al.21 investigated the formation of halogenated byproducts after chlorination of pure and tap water samples spiked with BP-3 (50 μg/L) in the absence and presence of low levels of bromide (maximum level of 10 μg/ L) and found mono- and dihalogenated byproducts (monobromo-, dibromo-, and bromochlorobenzophenone) and di- and trihalogenated forms of 3-methoxyphenol. Duirk et al.23 also studied the fate of BP-3 in the presence of an excess of chlorine and found chloroform as a stable transformation product. Furthermore, Yamamoto et al.44 had observed an increase in the mutagenic effects of BP-3 solutions after chlorination. However, these studies did not evoke the fate of BP-3 in seawater in which the high levels of bromide (65 mg/L) can have effects on the transformation pathways leading to different byproducts following chlorination. Hence, it seems important to determine the mechanisms of BP-3 transformation in chlorinated seawater with high bromide content such as in thalassotherapy centers. In these establishments, during summer periods, users engage in an alternating behavioral pattern involving sunbathing outside the pool (sunscreen application) and swimming in the pools (introduction of the applied products to the pool). Thus, a cocktail of organic compounds, including BP-3, is introduced to the pool, ready to react with HOBr/OBr−. As underlined by several authors, research on the fate of sunscreen products in chlorinated environments, such as swimming pools, is still very limited although these compounds were shown to contribute to the formation of DBPs.45,46 In addition, a realistic estimation of

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EXPERIMENTAL SECTION Materials. The UV filter BP-3 (Fluka, China), benzoic acid (ACS reagent, India), and 2,4,6-tribromo-3-methoxyphenol (TBMP) purchased from Sigma-Aldrich (Saint-Quentin Fallavier, France) were used. THM calibration mix containing chloroform (100.3 mg/L), bromodichloromethane (94.8 mg/ L), dibromochloromethane (94.6 mg/L), and bromoform (93.5 mg/L) was purchased from Supelco (Bellefonte, PA, USA), and tribromoacetaldehyde (97%) was purchased from Aldrich (United Kingdom). Artificial seawater (ASW) was prepared according to the ASTM International standard practice for the preparation of substitute ocean water (method D1141-98, 2013) (Table S1 in the Supporting Information (SI) summarizes ASW content). Chlorination was conducted with sodium hypochlorite (NaOCl) 5% purchased from Acros Organics (Illkirch, France). L-Ascorbic acid, crystalline, reagent grade (Sigma, China) was used as a quenching agent to stop the reactions at the desired times. All solutions were prepared in ultrapure water produced from a Millipore water system (resistivity >18 MΩ cm). Experimental Methods. Chlorination experiments of the UV filter BP-3 were carried out at molar ratios of 1:1, 1:10, and 1:25 (substrate:chlorine) and at temperatures of 25 °C, 30 °C, and 35 °C. These temperatures were chosen to guarantee proximity to temperatures found in seawater swimming pools as in thalassotherapy centers where temperatures can reach up to 38 °C.47 To conduct the reactions, glass vials with PTFE-lined screw caps of 65 mL capacities were filled with ASW and placed in water baths adjusted to the proper temperature. BP-3 was then added to the vials at a concentration of 100 μg/L (4.38.10−7 mol/ L). This concentration of BP-3, which is 30-fold higher than the levels already found in swimming pools, was chosen to allow the detection of BP-3 byproducts. Nevertheless, the dose of chlorine used in the experiment 1:25 corresponds to the level of chlorine (0.75 mg Cl2/L) that can be used in European real cases or to the minimal dose recommended by WHO. Practically, chlorination was launched by adding a corresponding volume of NaOCl solution so that the desired molar ratio of BP-3:chlorine was 9309

DOI: 10.1021/acs.est.5b00841 Environ. Sci. Technol. 2015, 49, 9308−9316

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Figure 1. Kinetics of formation of bromoform (CHBr3) and dibromochloromethane (CHBr2Cl) during chlorination of oxybenzone (BP-3) in seawater at various ratios and various temperatures.

Figure 2. Kinetics of formation of bromoform (CHBr3) (in gray lines) and disappearance of oxybenzone (BP-3) (in black lines) in seawater at 30 °C.

(1995). Details about the oven program are available in the Supporting Information (SI-1). Extracts obtained in LLE were analyzed to search for byproducts using quadrupole/time-offlight mass spectrometry (Synapt G2 HDMS, Waters, MA, USA) with electrospray ion (ESI) source and combined to an Acquity UPLC system (Waters). Chromatographic conditions are given in the Supporting Information (SI-2). Research for potential intermediates of BP-3 degradation included the utilization of GC-MS with electron ionization. Samples were injected in a Thermo Trace GC chromatograph interfaced to a Polaris Q ion trap mass spectrometer fitted with an external ionization source (70 eV) according to U.S.EPA Method 551.1 (1995). The chromatographic separation conditions are described in the Supporting Information section (SI-3).

established. L-ascorbic acid was used as a quenching agent to stop reactions at the desired time points. The first time point (t = 0 min) was obtained through the addition of ascorbic acid prior to the addition of chlorine. The vials had no headspace so that volatile byproducts would not be lost. Vials were placed away from sunlight to avoid any risk of photolysis. To extract the remaining BP-3 and the potentially formed byproducts, vials were acidified, and then liquid−liquid extraction (LLE) was performed by applying 5 mL of methyl tert-butyl ether (MTBE) of Chromosolv, HPLC grade (SigmaAldrich, Germany) to 50 mL aliquots of vial contents and shaking manually for 2 min. Subsequently, the organic phase was separated and submitted to analysis. Chlorination reactions for two commercially available byproducts of BP-3 identified in this study (TBMP and benzoic acid) were conducted in order to examine their reactivity and potential to produce bromoform. The same experimental protocol as in BP-3 chlorination was followed, with TBMP or benzoic acid being introduced as the substrate at 100 μg/L to react with chlorine (substrate:chlorine molar ratios of 1:1, 1:10, and 1:25) at 25 °C. Analytical Methods. Free residual bromine was measured by a Merck Spectroquant NOVA 60 (Darmstadt, Germany) at 525 nm with VWR DPD free chlorine-test (West Chester, Pennsylvania, USA) for samples of 10 mL. The analysis of THMs was performed using GC-ECD (PerkinElmer Clarus 580 system, Norwalk, CT, USA) and according to U.S.EPA Method 551.1

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RESULTS AND DISCUSSION

Formation of Bromoform. When adding HOCl/OCl− to bromide-rich waters, due to chlorine and bromide standard redox potentials, HOBr/OBr− is rapidly formed.34 Due to its high oxidizing capability, hypochlorous acid is the dominant reactive species for the reaction with halides (kHOCl ≥ 106 kClO‑).32 At first, a BrCl-type intermediate would be formed via the transfer of Clδ+ from hypochlorous acid to the bromide ion (Br−), followed by the hydrolysis of the BrCl intermediate into OBr− (reactions 1 and 2): HOCl + Br − → BrCl + OH− 9310

(1) DOI: 10.1021/acs.est.5b00841 Environ. Sci. Technol. 2015, 49, 9308−9316

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Figure 3. Kinetics formation of TTHM (Total Trihalomethanes, calculated as CHBr3) from chlorination of oxybenzone (BP-3) in seawater at 30 °C at a ratio BP-3:NaOCl = 1:25 ([BP-3]0= 100 μg·L−1 = 4.58 × 10−7 M; [NaOCl]0 = 1.095 × 10−5 M) during 120 h. Insert: Correlation line between moles of TTHM formed as a function of moles of bromine consumed.

BrCl + 2OH− → OBr − + Cl− + H 2O

The global reaction may be written as follows:

respectively) has demonstrated that the reaction was still proceeding and had to involve byproducts issued from the chlorination of BP-3. A long-term experiment (120 h) has also been conducted at the ratio 1:25 at 30 °C to check if the reaction could be complete. Figure 3 shows the kinetics of formation of TTHM, sum of all THMs analyzed and calculated as CHBr3, for a chlorination experiment of 100 μg·L−1 BP-3 (438 × 10−9 M) with an initial concentration of 1.095 × 10−5 M in NaOCl. After 60 min, no more BP-3 was detected, and the concentration of TTHM was 229.6 × 10−9 M (58.0 μg/L). Thereafter, TTHM were slowly produced during 80 h until a plateau was reached, corresponding to the full degradation of BP-3 (and the full consumption of residual bromine). A linear relationship between TTHMs and bromine demand, at t > 60 min, could also be confirmed (0.04 mol of CHBr3 formed per mole of bromine consumed, insert in Figure 3) in agreement with other findings.43,50,51 Consumption of bromine (or bromine demand) may be divided into two periods:52 − an initial phase of immediate consumption of bromine during the first 60 min, linked to the rapid reaction of HOBr with BP-3 (high reactivity of bromine with aromatic compounds, mostly by electrophilic substitutions); − a second slow consumption phase after the first 60 min, linked to the slowly reacting byproducts of BP-3 (brominated derivatives of BP-3, Br-BP). These two steps may be summarized as follows

(2) 32

HOCl + Br − → HOBr + Cl− k1 = kHOCl = 1.57.106 × exp(− 1620/T )

with kHOCl in M−1 s−1 and T, temperature, in Kelvin. In acidic solution, a HOCl acid-catalyzed reaction has also been described in the case of bromide by Nagy et al. (1988):48 HOCl + H+ + Br − ↔ H 2O + BrCl

In this way, after adding hypochlorous acid into bromidecontaining water, the only halide species are HOBr, OBr−, and Cl− and the highly reactive intermediate BrCl.48 As our experiments are carried out in buffered seawater (pH value close to 8.3 and an ionic strength close to 1 M), reactions will involve HOBr and OBr− (pKa = 8.8),49 reacting mainly with the deprotonated form of BP-3 (pKa = 7.56). Chlorination experiments carried out at the molar ratio 1:1 (BP-3:NaOCl) and at the three temperatures (25, 30, or 35 °C) did not lead to the formation of any THM, whereas those carried out at 1:10 and 1:25 led to the formation of bromoform (CHBr3) as the dominant THM, with concentrations reaching 8.0, 9.0, and 11.0 μg/L for the ratio 1:10 at 25, 30, and 35 °C, respectively, and 22.1, 28.9, and 40.9 μg/L for the ratio 1:25 at 25, 30, and 35 °C, respectively (Figure 1a). Besides bromoform, dibromochloromethane (CHClBr2) was also detected at a maximum level of 2.9 μg/L for the ratio 1:25 and at T = 35 °C (Figure 1b). Dichlorobromethane (CHCl2Br) and chloroform (CHCl3) were not detected. Figure 2 clearly demonstrates that experiments carried out in equimolar ratio (1:1) did not lead to the total degradation of BP3: only around 14.6% degradation yield of BP-3 within 60 min which explains the absence of detected formation of bromoform. However, the higher ratios led to the complete degradation of BP-3 within less than 30 min, with 0.03 mol of CHBr3 formed per mole of BP-3 consumed at a ratio 1:10 and, 0.15 mol of CHBr3 formed per mole of BP-3 at a ratio 1:25, after 60 min. The determination of residual bromine after 60 min (3.5 and 4.5 mg· L−1, expressed as free chlorine Cl2, at ratios 1:10 and 1:25,

k1

HOBr + BP‐3 → Br‐BP k2

HOBr + Br‐BP → TTHM

with k1 representing the rate constant for the rapid reaction (reaction of HOBr with BP-3), and k2 representing the rate constant for the slow reaction (reaction of HOBr with Br-BP). Chang et al.53 have derived the parallel first-order reaction model of chlorine decay to fit their experimental data in their study of chlorine reactions with models compounds (hydroxybenzene and hydroxybenzoic acids). 9311


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Figure 4. Reaction pathway of BP-3 in chlorinated seawater, based on identified byproducts by GC-MS and/or UPLC-ESI-MS.

equations (eqs 1 and 2) with [HOBr]R0 = f [HOBr]0 and [HOBr]S0 = (1−f)[HOBr]0, bromine concentration at any time is

Applying this model to the present case, and assuming that the two reactions are first-order in bromine, this reaction model may be modified as the following d[HOBr]R = −k1 × [HOBr] dt

[HOBr](t ) = [HOBr]0 × (f × exp( −k1t )

(1)

+ (1 − f ) × exp(−k 2t )

and d[HOBr]S = −k 2 × [HOBr] dt

(3)

where [HOBr](t) being the bromine concentration at any time t, [HOBr]0 being the initial bromine concentration, and f being the fraction of the bromine consumption attributed to rapid reactions. As depicted in Figure 3, the fast reaction of bromine with BP-3 occurred within the first 60 min. It is thus possible to experimentally determine k1 by plotting:

(2)

in which [HOBr]R is the hypobromous acid concentration participating in the hypothetical separate rapid reaction; [HOBr]S is the hypobromous acid concentration participating in the hypothetical separate slow reaction. Integrating these rate 9312


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Figure 5. Kinetics of formation and disappearance of BP-3 and of its identified byproducts during chlorination experiments carried out in seawater at a ration 1:10. Left y-axis is expressed in mol/L for BP-3, 2,4,6-tribromo-3-methoxyphenol -TBMP-, benzoic acid, bromal hydrate, and bromoform. Right yaxis is expressed in arbitrary units for mono- and dibromooxybenzone.

ln

more likely to undergo an electrophilic aromatic substitution in the presence of the electrophilic compound HOBr. Two isomers believed to correspond to the monobrominated BP-3 were identified tentatively based on their exact masses (spectra presented in Figures S4 and S5 in section SI-5 of the Supporting Information). These isomers had the same exact mass and exhibited the same mass spectra but appeared at slightly different retention times (chromatogram presented in Figure S6 in section 5-1 of the Supporting Information). Taking into consideration the ortho- and para-directing effect of the OH group on the phenolic moiety of BP-3, these isomers are believed to correspond to the ortho- and para-monobrominated BP-3 as already observed for other phenolic compounds by Acero et al.41 These two byproducts did not have equivalent levels as it appeared in the chromatogram (Figure S6). This difference might be explained by examining the structure of BP-3 which is characterized by a steric hindrance at the ortho position. This position is surrounded by both the hydroxyl and methoxy groups of the phenol moiety in contrast to the para position which is relatively more liberated. Consequently, it seemed that the superior peak corresponded to para-brominated BP-3, while the inferior peak corresponded to ortho-brominated BP-3. The importance of the impact of steric hindrance on the distribution of isomers in chlorination reactions of phenols was evoked in previous studies.41 Dibrominated BP-3 was also tentatively identified when chlorine was added in an equimolar ratio (Figure S7 in section SI-5 of the Supporting Information). Another dibrominated byproduct was also tentatively identified based on its exact mass by UPLC-ESI-MS (Figure S8 in section SI-5 of the Supporting Information). This compound was believed to be issued from the oxidation of the carbonyl group to an ester, through a reaction known as the Baeyer−Villiger rearrangement.54,55 Nevertheless, its levels could not be monitored over the experiment duration because of its very short half-life (detected one or two times within the duration of each experiment). When chlorine was added in equimolar proportions, its reaction with BP-3 did not generate tribrominated byproducts, unlike when it was added in excess (ratios 1:10 and 1:25). The addition of chlorine in excess triggered further bromination and led to the formation of two intermediates resulting from the hydrolysis of the previous dibrominated ester product: a phenolic product (2,4,6-tribromo-3-methoxyphenol -TBMP- Figure S9 in section SI-5 of the Supporting Information) and benzoic acid (identified by ESI-UPLC MS (Figure S10) and by GC-MS (Figure S11)). These two

[HOBr]0 = k1 × t (with t ≤ 60 min) [HOBr]

Similarly, it is possible to experimentally determine k2 by plotting the same relation but for t > 60 min. These two plots are represented in the Supporting Information (Figure S1 in section SI-4): the rapid and slow decay rate constants are k1 0.367 h−1 and k2 0.04 h−1, respectively. This latter is similar to the rate constant of TTHM formation (0.04 mol of TTHM formed per mole of mole of bromine consumed). Finally, considering that f is equal to 0.477 (fraction of the bromine demand used for the rapid reaction), the trends in bromine concentration may be expressed as [HOBr](t ) = [HOBr]0 × (0.477 × exp(− 0.367t ) + 0.523 × exp( −0.04t )

This relationship fits the trends in bromine consumption represented by our experimental data in Figure 3 (Figure S2 in the Supporting Information of section SI-4 presents the observed and the predictive bromine consumption). Values of k1 and k2 are consistent with those found by Heeb et al.34 who studied reactivity of bromine with aromatic compounds present in natural organic matter and who found a typical biphasic reaction: a fast initial phase followed by a slower one, with a rate constant around 100 times lower. Identification and Kinetics of Intermediates Involved in the Degradation Pathway of BP-3. Analysis of extracts obtained from reactions between BP-3 (MS spectrum presented in the Supporting Information in Figure S3 in section SI-5) and HOBr at the three different ratios and at different reaction times by UPLC-ESI-MS and GC-MS allowed the identification of several byproducts involved in the transformation pathway of BP-3 into CHBr3. Byproducts were identified tentatively based on their exact masses unless standards were found commercially. In that case the byproduct in question was identified based on its exact mass and on matching its retention time with the pure standard. Different byproducts were found depending on whether chlorine was added in excess or not. The global transformation pathway entailing all the identified transformation products is shown in Figure 4. The addition of chlorine in equimolar ratio (1:1) with respect to BP-3 generated monobrominated and dibrominated byproducts. The presence of the activating hydroxyl group in the phenolic moiety of BP-3 renders it more electron-dense and thus 9313


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Figure 6. Kinetics of formation and disappearance of BP-3 and of its identified byproducts during chlorination experiments carried out in seawater at a ration 1:25. Left y-axis is expressed in mol/L for BP-3, 2,4,6-tribromo-3-methoxyphenol -TBMP-, benzoic acid, bromal hydrate, and bromoform. Right yaxis is expressed in arbitrary units for mono- and dibromooxybenzone.

benzoic acid and eventually to provoke the cleavage of these byproducts explains the absence of bromoform when BP-3 was chlorinated at the ratio 1:1. The importance of the cleavage of TBMP in the pathway leading to bromoform formation was recognized when ASW was spiked with chlorine and TBMP or benzoic acid as starting product. These compounds constitute the two main moieties resulting from the cleavage of the ester product formed after the Baeyer−Villiger oxidation. The examination of the potential of these two degradation products of BP-3 to produce bromoform at 25 °C and at molar ratios 1:1, 1:10, and 1:25 (substrate:chlorine) allowed the determination of the pathway by which most of the bromoform formed in BP-3 chlorination experiments was formed. Figure S13 in section SI-7 of the Supporting Information shows that TBMP was the major moiety forming bromoform. TBMP degraded faster than benzoic acid. At the ratio 1:25, 88% of TBMP was degraded within 1 h and totally degraded within 22 h, as compared to only 47% and 60% of benzoic acid degraded within the same reaction durations, respectively. These findings confirm that CHBr3 originated primarily from TBMP and are in agreement with the assumption of Duirk et al.23 that the 3methoxyphenol moiety could be the primary functional group responsible for CHCl3 formation in BP-3 chlorination reactions in tap water. This study has demonstrated the potential of a widely used active ingredient of sunscreen formulations to form bromoform and other brominated DBPs following chlorination in seawaters. The chemical pathway of BP-3 transformation in chlorinated seawater was proposed based on the identified byproducts. The implication of the two moieties resulting from the cleavage of BP3 specifically benzoic acid and 2,4,6-tribromo-3-methoxyphenol (TBMP) in the formation of bromoform was evaluated with TBMP being the main moiety forming bromoform. Dibromochloromethane and bromal hydrate were also detected as minor byproducts. The occurrence of bromal hydrate in seawater swimming pools should be the subject of further studies as its higher toxicity in comparison to its chlorinated analogue (chloral hydrate) was already reported but remains insufficiently documented.58 These findings suggest the importance of taking PCPs worn by swimming pool users into consideration as potential precursors of DBPs, so showering with soapy water before entering indoor

degradation products were sufficiently stable to be monitored and were analyzed quantitatively. Kinetics obtained at the ratio 1:1 is presented in Figure S12 in section SI-6 of the Supporting Information. Figures 5 and 6 represent the kinetics of formation of the identified byproducts at the ratios 1:10 and 1:25, respectively. At the ratio 1:10, concentration of TBMP increased regularly up to around 11 × 10−9 M after 4 h of reaction, whereas concentration of benzoic acid reached 12.8 × 10−9 M (after 1 h of reaction) before declining gradually to 8 × 10−9 M after 4 h of reaction. At the ratio 1:25, the concentration of TBMP increased up to 3 × 10−9 M after 1 h, before declining to 1.9 × 10−9 M at the end of the experiment, whereas concentration of benzoic acid increased up to 25 × 10−9 M after 1 h of reaction, before declining to 4.7 × 10−9 M at the end of the experiment. Since standards of ortho- and para-monobrominated BP-3 (sum of these 2 isomers represented as Br-BP) and dibromo-BP-3 (Br2-BP) were not commercially available, the monitoring of their levels is represented in terms of their peak areas. The “pseudoconcentrations” of Br-BP and Br2-BP (estimated via peak areas) were approximately equivalent at a ratio of 1:1 throughout the entire reaction duration. Levels of Br2-BP increased up to around 400fold higher than the levels of Br-BP at the ratio 1:10 (at 45 min) and then up to around 100-fold higher at the ratio of 1:25 (at 45 min). These trends confirmed that Br2-BP was formed after the formation of Br-BP and that their half-lives were conditioned by the added level of chlorine (higher chlorine levels decreased their half-lives). Another degradation byproduct identified by GC-ECD (based on the matching retention time with the pure standard) was bromal hydrate (CBr3(CH(OH)2), which is the predominant form of tribromoacetaldehyde (CBr3CHO) in water. Very scarce data exist in the literature concerning the occurrence of this product in swimming pools. Only a level of 230 μg/L is reported in the WHO Guidelines for safe recreational water environments,27 quoting Baudish’s research report.56 This compound, in reference to its chlorinated analogue chloral hydrate,57 may easily hydrolyze to CHBr3 and formic acid. In the present study, the highest concentrations of bromal hydrate were detected after 30 min at 1.1 × 10−9 M (ratio 1:10) and 2.0 × 10−9 M (ratio 1:25), equivalent to 0.3 and 0.6 μg/L, respectively. Kinetics of Formation of CHBr3 from TBMP and Benzoic Acid. The inability of the added chlorine to produce TBMP and 9314


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(6) Gago-Ferrero, P.; Demeestere, K.; Díaz-Cruz, M. S.; Barcelo, D. Ozonation and peroxone oxidation of benzophenone-3 in water: Effect of operational parameters and identification of intermediate products. Sci. Total Environ. 2013, 443, 209−217. (7) Schlumpf, M.; Cotton, B.; Consciente, M.; Haller, V.; Steinmann, B.; Lichtensteiger, W. In vitro and in vivo estrogenicity of UV screens. Environ. Health Persp. 2001, 109 (3), 239−244. (8) Zucchi, S.; Bluethgen, N.; Ieronimo, A.; Fent, K. The UV-absorber benzophenone-4 alters transcripts of genes involved in hormonal pathways in zebrafish (Danio rerio) eleuthero-embryos and adult males. Toxicol. Appl. Pharmacol. 2011, 250, 137−146. (9) Kunz, P. Y.; Fent, K. Estrogenic activity of ternary UV filter mixtures in fish (Pimephales promelas) - an analysis with nonlinear isobolograms. Toxicol. Appl. Pharmacol. 2009, 234, 77−88. (10) Santos, A. J. M.; Miranda, M. S.; Esteves da Silva, J. C. G. The degradation products of UV filters in aqueous and chlorinated aqueous solutions. Water Res. 2012, 46, 3167−3176. (11) Sobek, A.; Bejgarn, S.; Rudén, C.; Molander, L.; Breitholtz, M. In the shadow of the Cosmetic Directive - Inconsistencies in EU environmental hazard classification requirements for UV-filters. Sci. Total Environ. 2013, 461−462, 706−711. (12) Cosmetic Product Regulation (EC) # 1223/2009 of the European Parliament and of the Council of 30 November 2009, Official Journal of the European Union. (13) Sarveiya, V.; Risk, S.; Benson, H. A. E. Liquid chromatographic assay for common sunscreen agents: application to in vivo assessment of skin penetration and systemic absorption in human volunteers. J. Chromatogr. B: Anal. Technol. Biomed. Life Sci. 2004, 803, 225−231. (14) National Toxicology Program. http://ntp.niehs.nih.gov/ (accessed July 2, 2015). (15) Vione, D.; Caringella, R.; De Laurentiis, E.; Pazzi, M.; Minero, C. Phototransformation of the sunlight filter benzophenone-3 (2-hydroxy4-methoxybenzophenone) under conditions relevant to surface waters. Sci. Total Environ. 2013, 463−464, 243−251. (16) Balmer, M. E.; Buser, H. R.; Müller, M. D.; Poiger, T. Occurrence of some organic UV filters in wastewater, in surface waters, and in fish from Swiss lakes. Environ. Sci. Technol. 2005, 39, 953−962. (17) Grabicova, K.; Fedorova, G.; Burkina, V.; Steinbach, C.; SchmidtPosthaus, H.; Zlabeka, V.; Kroupova, H. K.; Grabic, R.; Randak, T. Presence of UV filters in surface water and the effects of phenylbenzimidazole sulfonic acid on rainbow trout (Oncorhynchus mykiss) following a chronic toxicity test. Ecotoxicol. Environ. Saf. 2013, 96, 41− 47. (18) Barón, E.; Gago-Ferrero, P.; Gorga, M.; Rudolph, I.; Mendoza, G.; Zapatac, A. M.; Diaz-Cruz, S.; Barra, R.; Ocampo-Duquec, W.; Páez, M.; Darbra, R. M.; Eljarrat, E.; Barceló, D. Occurrence of hydrophobic organic pollutants (BFRs and UV-filters) in sediments from South America. Chemosphere 2013, 92, 309−316. (19) Negreira, N.; Rodriguez, I.; Ramil, M.; Rubi, E.; Cela, R. Optimization of pressurized liquid extraction and purification conditions for gas chromatography-mass spectrometry determination of UV filters in sludge. J. Chromatogr. A 2011, 1218 (2117), 211−217. (20) Jeon, H. K.; Chung, Y.; Ryu, J. C. Simultaneous determination of benzophenone-type UV filters in water and soil by gas chromatography−mass spectrometry. J. Chromatogr. A 2006, 1131, 192−202. (21) Negreira, N.; Canosa, P.; Rodriguez, I.; Ramil, M.; Rubi, E.; Cela, R. Study of some UV filters stability in chlorinated water and identification of halogenated by-products by gas chromatography− mass spectrometry. J. Chromatog. A 2008, 1178, 206−214. (22) Liu, Q.; Chen, Z.; Wei, D.; Du, Y. Acute toxicity formation potential of benzophenone-type UV filters in chlorination disinfection process. J. Environ. Sci. 2014, 26, 440−447. (23) Duirk, S. E.; Bridenstine, D. R.; Leslie, D. C. Reaction of benzophenone UV filters in the presence of aqueous chlorine: Kinetics and chloroform formation. Water Res. 2013, 47, 579−587. (24) National Swimming Pool Foundation (NSPF), NSPF Certified Pool-spa Operator Handbook; National Swimming Pool Foundation: Colorado Springs, CO, 2010.

seawater swimming pool in order to reduce inputs of sunscreens to pools may be proposed. Indeed, although some sunscreens claim to be “waterproof” or “water-resistant”, few studies demonstrated that they only possess between 10 and 30% water-resistance retention,59 and thus, could be washed off after one single immersion in the pool. Then in the pool, UV filters react with disinfectants, so transformation byproducts are formed. In this way, it seems important to include the assessment of the toxicity of the transformation byproducts of UV filters in swimming pools in toxicity/safety evaluation of sunscreens.

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ASSOCIATED CONTENT

* Supporting Information S

Table S1 lists the salts used to reconstitute artificial seawaters. SI1 summarizes the experiment conditions used for GC-ECD analysis of THMs. SI-2 presents the parameters used for UPLCESI-MS determination of BP-3 byproducts, whereas SI-3 presents parameters of GC-MS. Figure SI-4 presents the curves used for the determination of rapid and slow decay rates constants of bromine during chlorination of BP-3 in seawater. SI5 presents the mass spectra of BP-3 and its byproducts as determined either by UPLC-ESI-MS or by GC-MS. SI-6 presents kinetics of the appearance of bromoform when chlorination experiments were conducted directly with TBMP or benzoic acid. The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.5b00841.

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AUTHOR INFORMATION

Corresponding Author

*Phone: 33 (0)413551031. Fax: 33 (0)413551060. E-mail: [email protected]. Corresponding author address: AixMarseille University-CNRS, Faculty of Sciences, Department of Chemistry, Laboratory of Environmental Chemistry, 3 place Victor Hugo - case 29, CS80249, F-13331 Marseille cedex 3, France. Present Address †

INRA, UMR 1347 Agroecology, 21000 Dijon, France.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Tarek Manasfi acknowledges the Doctoral School of “Environmental Sciences” (ED251) at Aix-Marseille University and the French Ministry of Higher Education and Research for the doctoral scholarship.

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REFERENCES

(1) Jansen, R.; Osterwalder, U.; Wang, S. Q.; Burnett, M.; Lim, H. W. Photoprotection: Part II. Sunscreen: Development, efficacy, and controversies. J. Am. Acad. Dermatol. 2013, 69 (6), 867.e1−867.e14. (2) Brausch, J. M.; Rand, G. M. A review of personal care products in the aquatic environment: Environmental concentrations and toxicity. Chemosphere 2011, 82, 1518−1532. (3) Diaz-Cruz, M. S.; Llorca, M.; Barcelo, D. Organic UV filters and their photodegradates, metabolites, and disinfection by-products in the aquatic environment. TrAC, Trends Anal. Chem. 2008, 27 (10), 873− 887. (4) Poiger, T.; Buser, H.; Balmer, M. E.; Bergqvist, P.; Müller, M. Occurrence of UV filter compounds from sunscreens in surface waters: regional mass balance in two Swiss lakes. Chemosphere 2004, 55, 951− 963. (5) Balmer, M. E.; Buser, H. R.; Müller, M. D.; Poiger, T. Occurrence of some organic UV filters in wastewater, in surface waters, and in fish from Swiss lakes. Environ. Sci. Technol. 2005, 39, 953−962. 9315


Article

Environmental Science & Technology (25) Parinet, J.; Tabaries, S.; Coulomb, B.; Vassalo, L.; Boudenne, J.-L. Exposure levels to brominated compounds in seawater swimming pools treated with chlorine. Water Res. 2012, 46 (3), 828−836. (26) ANSES (French Agency for Food, Environmental and Occupational Health and Safety), Health risk assessment in swimming pools. Part 1: public swimming pools. 2010.https://www.anses.fr/fr/system/ files/EAUX2007sa0409Ra.pdf (accessed July 2, 2015). (27) World Health Organization. Guidelines for Safe Recreational Water Environments. volume 2, Swimming Pools and Similar Environments; WHO Press: Geneva, 2006. (28) Keuten, M. G. A.; Peters, M. C. F. M.; Daanen, H. A. M.; de Kreuk, M. K.; Rietveld, L. C.; van Dijk, J. C. Quantification of continual anthropogenic pollutants released in swimming pools. Water Res. 2014, 53, 259−270. (29) Poiger, T.; Buser, H. R.; Muller, M. D. Verbrauch, Vorkommen in Oberflachengewassern und Verhalten in der Umwelt von Substanzen, die als UV-Filter in Sonnenschutzmitteln eingesetzt werden; Bundesamt fur Umwelt, Wald, und Landschaft (BUWAL): Bern, Switzerland, 2001. (30) Lambropoulou, D. A.; Giokas, D. L.; Sakkas, V. A.; Albanis, T. A.; Karayannis, M. I. Gas chromatographic determination of 2-hydroxy-4methoxybenzophenone and octyldimethyl-paminobenzoic acid sunscreen agents in swimming pool and bathing waters by solid-phase microextraction. J. Chromatogr. A 2002, 967 (2), 243−253. (31) Giokas, D. L.; Sakkas, V. A.; Albanis, T. A. Determination of residues of UV filters in natural waters by solid-phase extraction coupled to liquid chromatography-photodiode array detection and gas chromatography-mass spectrometry. J. Chromatogr. A 2004, 1026, 289−293. (32) Deborde, M.; von Gunten, U. Reactions of chlorine with inorganic and organic compounds during water treatment - Kinetics and mechanisms: A critical review. Water Res. 2008, 42, 13−51. (33) Voudrias, E. A.; Reinhard, M. Reactivities of hypochlorous and hypobromous acid, chlorine monoxide, hypobromous acidium ion, chlorine, bromine, and bromine chloride in electrophilic aromatic substitution reactions with p-xylene in water. Environ. Sci. Technol. 1988, 22, 1049−1056. (34) Heeb, M. B.; Criquet, J.; Zimmermann-Steffens, S. G.; von Gunten, U. Bromine production during oxidative water treatment of bromide-containing waters and its reactions with inorganic and organic compounds: A critical review. Water Res. 2014, 48, 15−42. (35) Kanan, A.; Karanfil, T. Formation of disinfection by-products in indoor swimming pool water: the contribution from filling water natural organic matter and swimmer body fluids. Water Res. 2011, 45 (2), 926− 932. (36) Richardson, S. D.; Plewa, M. J.; Wagner, E. D.; Schoeny, R.; DeMarini, D. M. Occurrence, genotoxicity and carcinogenicity of regulated and emerging disinfection byproducts in drinking water: a review and roadmap for research. Mutat. Res., Rev. Mutat. Res. 2007, 636, 178−242. (37) Fabbricino, M.; Korshin, G. V. Modeling disinfection byproducts formation in bromide-containing waters. J. Hazard. Mater. 2009, 168 (2−3), 782−786. (38) Lee, J.; Ha, K. T.; Zoh, K. D. Characteristics of trihalomethane (THM) production and associated health risk assessment in swimming pool waters treated with different disinfection methods. Sci. Total Environ. 2009, 407 (6), 1990−1997. (39) Gallard, H.; Pellizzari, F.; Croue, J. P.; Legube, B. rate constants of reactions of bromine with phenols in aqueous solution. Water Res. 2003, 37 (12), 2883−2892. (40) Hua, G.; Reckhow, D. A. Comparison of disinfection byproduct formation from chlorine and alternative disinfectants. Water Res. 2007, 41, 1667−1678. (41) Acero, J. L.; Piriou, P.; von Gunten, U. Kinetics and mechanisms of formation of bromophenols during drinking water chlorination: assessment of taste and odor development. Water Res. 2005, 39 (13), 2979−2993. (42) Rebenne, L. M.; Gonzalez, A. C.; Olson, T. M. Aqueous chlorination kinetics and mechanism of substituted dihydroxybenzenes. Environ. Sci. Technol. 1996, 30 (7), 2235−2242.

(43) Gallard, H.; von Gunten, U. Chlorination of natural organic matter: kinetics of chlorination and of THM formation. Water Res. 2002, 36 (1), 65−74. (44) Yamamoto, T.; Nakajima, D.; Goto, S.; Onodera, S.; Yasuhara, A.; Sakai, S. I.; Soma, M. Mutagenicity of chlorination products of benzophenone and its derivative. Kankyo Kagaku 2004, 14 (2), 335− 342. (45) Teo, T. L. L.; Coleman, H. M.; Khan, S. J. Chemical contaminants in swimming pools: occurrence, implications and control. Environ. Int. 2015, 76, 16−31. (46) Chowdhury, S.; Alhooshani, K.; Karanfil, T. Disinfection byproducts in swimming pool: occurrences, implications and future needs. Water Res. 2014, 53, 68−109. (47) Crecente, J. M.; Santé, I.; Díaz, C.; Crecente, R. A multicriteria approach to support the location of thalassotherapy (seawater therapy) resorts: Application to Galicia region, NW Spain. Landscape. Urban. Plan. 2012, 104 (1), 135−147. (48) Nagy, J. C.; Kumar, K.; Margerum, D. W. Non-metal kinetics: oxidation of iodide by hypochlorous acid and nitrogen trichloride measured by the pulsed-accelerated-flow method. Inorg. Chem. 1988, 27, 2773−2780. (49) Lahoutifard, N.; Lagrange, P.; Lagrange, J.; Scott, S. L. Kinetics and mechanism of nitrite oxidation by HOBr/BrO− in atmospheric water and comparison with oxidation by HOCl/ ClO−. J. Phys. Chem. A 2002, 106 (49), 11891−11896. (50) Chiang, P. C.; Chang, E. E.; Chuang, C. C.; Liang, C. H.; Huang, C. P. Evaluating and elucidating the formation of nitrogen-contained disinfection by-products during pre-ozonation and chlorination. Chemosphere 2010, 80, 327−333. (51) Xu, B.; Tian, F. X.; Hu, C. Y.; Lin, Y. L.; Xia, S. J.; Rong, R.; Li, D. P. Chlorination of chlortoluron: Kinetics, pathways and chloroform formation. Chemosphere 2011, 83, 909−916. (52) Jadas-Hécart, J.; El Morer, A.; Stitou, M.; Bouillot, P.; Legube, B. The chlorine demand of a treated water. Water Res. 1992, 26 (8), 1073− 1084. (53) Chang, E. E.; Chiang, P. C.; Chao, S. H.; Lin, Y. L. Relationship between chlorine consumption and chlorination by-products formation for model compounds. Chemosphere 2006, 64, 1196−1203. (54) Negreira, N.; Rodríguez, I.; Rodil, R.; Cela, R. Assessment of benzophenone-4 reactivity with free chlorine by liquid chromatography quadrupole time-of-flight mass spectrometry. Anal. Chim. Acta 2012, 743, 101−110. (55) Xiao, M.; Wei, D.; Li, L.; Liu, Q.; Zhao, H.; Du, Y. Transformation mechanism of benzophenone-4 in free chlorine promoted chlorination disinfection. Water Res. 2013, 47 (16), 6223−6233. (56) Baudisch, C.; Pansch, G.; Prösch, J.; Puchert, W. Determination of volatile halogenated hydrocarbons in chlorinated swimming pool water; Research report; Außenstelle Schwerin, Landeshygieneinstitut Mecklenburg-Vorpommern: in German, 1997. (57) Cimetiere, N.; De Laat, J. Effects of UV-dechloramination of swimming pool water on the formation of disinfection by-products: A lab-scale study. Microchem. J. 2014, 112, 34−41. (58) Butler, T. C. Bromal hydrate and chloral hydrate; a pharmacological contrast and its chemical basis. J. Pharmacol. Exp. Ther. 1948, 94 (4), 401−411. (59) Poh Agin, P. Water resistance and extended wear sunscreens. Dermatol. Clin. 2006, 24 (1), 75−79.

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Degradation Products of Benzophenone-3 in Chlorinated Seawater

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