Health Risk Assessment for Bromate (Bro3–) Traces in Ozonated Indian
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Journal of Environmental Protection, 2011, 2, 571-580 doi:10.4236/jep.2011.25066Published Online July 2011 (http://www.scirp.org/journal/jep) – Health Risk Assessment for Bromate (BrO3 ) Traces in Ozonated Indian Bottled Water Ajay Kumar1*, Sabyasachi Rout1, Rakesh Kumar Singhal2 1Health Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India; 2Analytical Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India. Email: [email protected] Received May 19th, 2011; revised June 14th, accepted July 11th, 2011. ABSTRACT For this study, bromide and bromate ions in various commercial brands of Indian bottled water samples were estimated using ion chromatography. The measured mean concentration of bromide and bromate ions in water samples was found to be 28.13 µg/L and 11.17 µg/L respectively. The average level of bromate in Indian bottled water was found to be slightly higher (~ 12%) than the acceptable limits (10 µg/L) recommended by USEPA (US Environmental Protection Agency). Though, kinetically, it is predicted that 62.5% (6.25 µg/L) of bromide in bottled water is needed to convert into bromate upon ozonation to exceed the minimum acceptable limits, but the average formation of bromate deter- mined to be only 26.77% of the predicted concentration. Bromate concentration in bottled water showed a strong cor- relation with bromide suggesting that its formation in water is very much influenced and controlled by bromide content. – The objective of the present study was to determine the BrO3 content in commercially available different brands of bottled drinking water in India and to estimate the health risks to population due to ingestion. Results of estimated ex- cess cancer risk and chemical toxicity risk to Indian population due to ingestion of bottled water were presented and discussed. Keywords: Bromide, Bromate, Excess Cancer Risk, Chemical Toxicity Risk, Bottled Water 1. Introduction chemical characteristics of bromide compounds are low concentration in most rock-forming minerals and gene- 1.1. Genesis rally low bioconcentrations in aqueous systems. Because During the 1970’s, it was realized that the chlorination of of these characteristics, it behaves as conservative spe- drinking water produced carcinogenic disinfection by cies and widely used as tracers in hydrological systems. products (DBPs) such as trihalomethane. Since then, al- During the evaporite deposits, bromine shows some ad- ternative disinfection methods that minimize the produc- sorption characteristics particularly at low pH, on Kao- tion of toxic by-products have been investigated. Ozona- linite and iron oxide surface. tion has emerged as one of the most promising alterna- The sources of bottled water in India are mainly sur- tives to chlorination [1]. Although ozonation is already face and subsurface water like river water, lake water and an established method of water purification in the water ground water. The common technique for preparation of industry, it suffers from a major problem which is attra- bottled water is based on reverse osmosis, ultra filtration, cting increasing concern, namely the formation of bro- ozonisation, electrolytic methods etc. which are itself the mate ions due to oxidation of bromide ion. removal technique of bromide ion. In spite of applying the removal processes, trace quantities of bromide are 1.2. Bromine found in the bottled water. Bromine is an important precursor to bromate in drinking The bottled water is a highly regulated as a food pro- water. Bromine has both natural and anthropogenic duct by FDA (Food Development Authority) under the sources. Natural sources include seawater, subsurface Federal Food, Drug and Cosmetic Act (FFDCA), subject brines and evaporite deposits. Anthropogenic sources for to federal, state, and industry standards and includes in bromine include pesticides, medicines and industrial sol- smaller containers as well as larger containers distributed vents, gasoline additives and water purification. Hydro to the home and markets. Copyright © 2011 SciRes. JEP – 572 Health Risk Assessment for Bromate (BrO3 ) Traces in Ozonated Indian Bottled Water 1.3. Bromate in electrolytically generated hypochlorous acid solutions when bromide is present in the brine [10]. Since bromate Bromate is not normally found in water. Conversion of contains 62.5% (0.625) bromide only hence this fractions bromide to bromate upon ozonation may be affected by need to be converted to form bromate upon ozonation to physico-chemical parameters including natural organic exceed maximum acceptable concentration. The follow- matter, pH, temperature and some other factors. The rel- ing equations show the pathway by which bromide (Br–) ative increase of bromate depends on measures used for – is oxidized by ozone to bromate (BrO3 ) through the in- comparison (over time or as a function of concentration –) termediate formation of hypobromite (OBr . These of bromide (C) × retention time with the amount of equations also show that ozone does not oxidize hypo- ozone (T)). The use of CT has been suggested as a more bromous acid (HOBr) to bromate. Since increased acid useful indicator to describe the relative rate of bromate + (H3O ) will favor the formation of hypobromous acid, formation because it also gives a simultaneous descriptor this suggests that ozonation at a low pH will tend to for disinfection efficiency [2]. The rate of formation of minimize bromate formation [11]. bromate ion may also increase with temperature [3,4]. In – – Br + O3 + H2O —> HOBr + O2 + OH addition, many studies on the effect of alkalinity on the + – HOBr + H2O —> H3O + OBr formation of bromate during ozonation indicate that in- – – OBr + 2O3 —> BrO3 + 2O2 creased alkalinity increases bromate formation [5]. How- HOBr + O3 —> No Reaction ever, the rate of formation of bromate during ozonation is also affected by ozone characteristics. Thus, a smaller 1.4. Provisional Guideline Values CT may result because ozone becomes less stable with Bromate is mutagenic both in vitro and in vivo. [12,13] increasing temperature and/or alkalinity. All factors be- has classified potassium bromate in Group 2B (possibly ing equal, bromide concentration and ozone dose are the carcinogenic to humans), concluding that there is inade- best predictors of bromate formation during ozonation quate evidence of carcinogenicity in humans but suffi- [6]. It should be noted that some of the studies demon- cient evidence of carcinogenicity in experimental ani- strating high rates of conversion of bromide to bromate mals. [14] has classified bromate as a probable human are pure laboratory studies with very high bromide levels carcinogen by the oral route of exposure under the 1986 and thus may not be representative of conversion rates at EPA guidelines for Carcinogen Risk Assessment [15] on environmentally relevant doses. the basis of adequate evidence of carcinogenicity in male In the ozonised bottled water, naturally occurring and female rats. Under the 1999 EPA draft Guidelines bromide causes a catalytic disintegration of ozone and for Carcinogen Risk Assessment [16], bromate is likely – forms hypobromite (OBr ) as an intermediate product to be a human carcinogen by the oral route; the data on which is predominantly present at higher pH values, but the carcinogenicity of bromate via the inhalation route at lower pH, more hypobromous acid (HOBr) is formed. are inadequate for an assessment of its human carcino- Hypobromite reacts further with an excess of ozone to genic potential. [17] has classified bromate as probably form bromate. Hypobromous acid does not react further carcinogenic to humans (sufficient evidence in animals; with ozone; therefore, at low pH, no bromate is formed. no data in humans). At this time, there is not sufficient In the presence of organic matter, HOBr leads to the evidence to conclude the mode of carcinogenic action for formation of brominated organic compounds, such as potassium bromated [6,13,14,18]. Because of insufficient bromoform, mono- and dibromoacetic acid, dibromoace- information on the mode of carcinogenic action of bro- tonitrile, bromopicrin and especially cyanogen bromide. mate, IPCS (2000) developed both a carcinogenicity as- Under certain conditions, bromate may also be formed in sessment based on the linearized multistage model as concentrated hypochlorite solutions used to disinfect well as a TDI based on a non-linear approach for the car- drinking-water [6]. This reaction is due to the presence of cinogenicity of bromate. A TDI of 1 μg/kg of body weight bromide in the raw materials (chlorine and sodium hy- was calculated based on a no-effect level for the forma- droxide) used in the manufacture of sodium hypoch- lo- tion of renal cell tumours in rats at 1.3 mg/kg of body rite and to the high pH of the concentrated solution. weight per day in the [19] study and the use of an uncer- Bromide is not oxidized by chlorine dioxide, so the use tainty factor of 1000 (10 each for inter- and intraspecies of chlorine dioxide will not generate hypobromous acid, variation and 10 for possible carcinogenicity). The IPCS hypobromite ion or bromate [7]. Although bromate can (2000) value of 0.1 μg/kg of body weight per day for a be formed on simultaneous exposure to chlorine dioxide 10–5 excess lifetime cancer risk level was based on an and light, the reaction is thermodynamically unfavour- increased incidence of renal tumours in male rats given able and bromate is unlikely to be formed under water potassium bromate in drinking-water for 2 years using treatment conditions [8,9]. Bromate can also be formed the same study [19]. The upper-bound estimate of the Copyright © 2011 SciRes. JEP – Health Risk Assessment for Bromate (BrO3 ) Traces in Ozonated Indian Bottled Water 573 cancer potency for bromate is 0.19 per mg/kg of body tober, 2010. During collection of bottled water, ozona- weight per day. The concentrations in drinking water tion for purification as well as date of packing were taken associated with upper-bound excess lifetime cancer risks care of to avoid any discrepancies.