Resources: Bromide in Surface Water


What is bromide and where do you find it naturally in surface waters?

Bromine (Br2) is a chemical element (atomic number 35) belonging to the highly reactive halogen group, which also includes fluorine, chlorine, and iodine. Halogens are oxidizing agents that form anions by accepting an electron (their outer electron shell is one electron short of being full). Bromide (Br-) is the anion of the element Bromine. Since elemental bromide is highly reactive, it does not occur freely in nature, but instead exists as salts (e.g. NaBr, AgBr) or acids (e.g. HBr, HOBr; WHO 2018). Bromide naturally occurs in the earth’s crust, seawater, salt lakes, and underwater brines (VanBriesen 2014). Fossil fuels, such as coal, also contain varying concentrations of bromide (Kolker et al. 2006). The highest natural concentrations of bromide are found in seawater (66-68 mg/L), shale geologic formations (24 mg/kg), and coastal groundwater (2.3 mg/L) and soils (850 mg/kg). In the United States, inland groundwaters, fresh surface waters, and drinking water sources do not typically have naturally high bromide values (0.014-0.2 mg/L; VanBriesen 2014).

What are the risks associated with bromide in source water?

Bromide in itself is not a risk to human or ecosystem health when present in source water (WHO 2009). However, during drinking water decontamination, bromide reacts with natural organic matter (NOM) and chemical disinfectants present in source water to create brominated disinfection byproducts (DBPs), which may pose a significant threat to human health (Richardson et al. 2007). During the drinking water treatment process, chemical disinfectants are used to remove pathogenic microbes and nuisance metals. Hundreds of species of DBPs can be produced at various stages of the drinking water disinfection process depending on source water characteristics, disinfectant type, engineering practices, water distribution network characteristics, and climate (Krasner 2009). Since the 1970’s when DBPs were first discovered in finished drinking water (Rook 1974), many toxicological and epidemiological studies have examined the relationship between DBP exposure and potential human health consequences (Charrois and Hrudey 2012). Elevated bromide in source water is particularly concerning because brominated DBPs have been shown to be more carcinogenic and cytotoxic than their chlorinated analogs (Richardson et al. 2007, Pan et al. 2014, Ersan et al. 2019). Importantly, even a relatively low increase in source water bromide concentration can shift the species and quantity of DBPs produced during drinking water disinfection to a greater number of brominated DBPs (Singer and Reckhow 2011, Mctigue et al. 2014) escalating the risk of adverse human health effects (Richardson et al. 2007, Ersan et al. 2019). Recently, Regli et al. (2015) estimated an increased risk of bladder cancer associated with elevated source water bromide at concentrations equivalent those frequently associated with anthropogenic contamination.

What are anthropogenic drivers of increasing bromide concentrations?

Historical bromide uses include early photograph development (silver bromide) and sedatives in human medicine (potassium bromide) during the 18th and 19th centuries (Soltermann et al. 2016). The first significant anthropogenic releases of bromide into the environment occurred in the 1920s-1990s when brominated compounds were added to gasoline to prevent lead deposition in the engine (Thomas et al. 1997). Engine combustion of the added bromine released methyl bromide gas (also called bromomethane) into the environment. The use of methyl bromide as an agricultural fungicide also represented a significant anthropogenic release of bromide until its use was largely phased out by the 2000s (Taylor 1994). Finally, bromide has been released as a waste product of potassium (potash) mining activities and found to elevate surface water bromide concentrations in several European countries, particularly the River Rhine (Flury and Papritz 1993) and the Llobregat River (Ventura and Rivera 1985). Salt mining still a major industry in various parts of the world and continues to create water quality issues when brines pollute source waters (Valero and Arbós 2010). Current anthropogenic sources of bromide include energy extraction and utilization, coal-fired power plants, water treatment, flame retardants, pre-planting and post-harvest biocides, agricultural herbicides, municipal waste incinerators, landfill leachate, road deicers, and pharmaceuticals (Vainikka and Hupa 2012, Mctigue et al. 2014, VanBriesen 2014, Winid 2015).

Why is it important to understand what is driving increasing bromide concentrations?

Elevated levels of bromide in source water leads to a higher production of brominated DBPs following drinking water disinfection (Cowman and Singer 1996). Brominated DBPs are more carcinogenic than their chlorinated analogs, meaning that there are greater human health risks associated with drinking, food preparation, and bathing with chemically-disinfected water (Richardson et al. 2007, Yang et al. 2014). Also, greater source water bromide levels can lead to increased formation of unregulated DBP classes, including halonitromethanes, haloamides, haloacetronitriles (Krasner et al. 2006, Pressman et al. 2010), which may be more harmful than regulated DBPs (Richardson et al. 2007). Source water bromide concentration is one of the most important DBP formation factors and elevated bromide can lead to as much as a two-fold increase in both regulated and unregulated DBPs (Hua et al. 2006, Sfynia 2017). Short-term exposure to high levels of DBPs has been weakly associated with restricted fetal growth (small for gestational age; Grellier et al. 2010), while long-term exposure to DBPs is consistently associated with an increased risk of urinary bladder cancer (Villanueva et al. 2003, 2004, Costet et al. 2011). Identifying drivers of increasing bromide concentrations in source water is essential because once bromide levels are elevated, there are no practical methods to remove the anion prior to disinfection (Rivera-Utrilla et al. 2019). Further, there are no practical methods available to reduce the number of brominated DPBs in finished water following drinking water treatment (Rivera-Utrilla et al. 2019). The best method to control bromide levels in source water and prevent the formation of brominated DBPs in finished drinking water is to regularly monitor bromide levels and if elevated levels are detected, then identify and stop anthropogenic inputs of bromide.

This information was prepared by faculty and students from the University of Georgia as part of a research program funded by the SFY2017 Regional Water Plan Seed Grant, “Bromide Concentrations in Surface Drinking Water Sources for Butts County” funded through the Georgia Environmental Protection Division.

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Charrois, J., and S. Hrudey. 2012. Disinfection By-Products and Human Health. IWA Publishing, London.

Costet, N., Villanueva, C.M., Jaakkola, J.J.K., Kogevinas, M., Cantor, K.P., King, W.D., Lynch, C.F., Nieuwenhuijsen, M.J. and Cordier, S., 2011. Water disinfection by-products and bladder cancer: is there a European specificity? A pooled and meta-analysis of European case–control studies. Occupational and environmental medicine, 68(5), pp.379-385.

Cowman, G.A. and Singer, P.C., 1995. Effect of bromide ion on haloacetic acid speciation resulting from chlorination and chloramination of aquatic humic substances. Environmental science & technology, 30(1), pp.16-24.

Ersan, M. S., C. Liu, G. Amy, and T. Karanfil. 2019. The interplay between natural organic matter and bromide on bromine substitution. Science of the Total Environment 646:1172–1181.

Flury, M., and A. Papritz. 1993. Bromide in the Natural Environment: Occurrence and Toxicity. Journal of Environment Quality 22:747.

Grellier, J., J. Bennett, E. Patelarou, R. B. Smith, M. B. Toledano, L. Rushton, D. J. Briggs, and M. J. Nieuwenhuijsen. 2010. Exposure to disinfection by-products, fetal growth, and prematurity: A systematic review and meta-analysis. Epidemiology 21:300–313.

Hrudey, S. E. 2009. Chlorination disinfection by-products, public health risk tradeoffs and me. Water Research 43:2057–2092.

Hua, G., D. A. Reckhow, and J. Kim. 2006. Effect of bromide and iodide ions on the formation and speciation of disinfection byproducts during chlorination. Environmental Science and Technology 40:3050–3056.

Kolker, A., Senior, C. L., & Quick, J. C. (2006). Mercury in coal and the impact of coal quality on mercury emissions from combustion systems. Applied geochemistry, 21(11), 1821-1836.

Krasner, S. W., H. S. Weinberg, S. D. Richardson, S. J. Pastor, R. Chinn, M. J. Sclimenti, G. D. Onstad, and A. D. Thruston. 2006. Occurrence of a new generation of disinfection byproducts. Environmental Science and Technology 40:7175–7185.

Mctigue, N. E., D. A. Cornwell, K. Graf, and R. Brown. 2014. Occurrence and consequences of increased bromide in drinking water sources. Journal – American Water Works Association 106:E492–E508.

Nieuwenhuijsen, M. J., Grellier, J., Iszatt, N., Martinez, D., Rahman, M. B., & Villanueva, C. M. (2010). Literature review of meta-analyses and pooled analyses of disinfection by-products in drinking water and cancer and reproductive health outcomes. Contaminants of Emerging Concern in the Environment: Ecological and Human Health Considerations, 1048.

Nieuwenhuijsen, M. J., Martinez, D., Grellier, J., Bennett, J., Best, N., Iszatt, N., … & Toledano, M. B. (2009). Chlorination disinfection by-products in drinking water and congenital anomalies: review and meta-analyses. Environmental Health Perspectives, 117(10), 1486-1493.

Pan, Y., X. Zhang, E. D. Wagner, J. Osiol, and M. J. Plewa. 2014. Boiling of simulated tap water: Effect on polar brominated disinfection byproducts, halogen speciation, and cytotoxicity. Environmental Science and Technology 48:149–156.

Pressman, J. G., Richardson, S. D., Speth, T. F., Miltner, R. J., Narotsky, M. G., Hunter, III, E. S., … & Krasner, S. W. (2010). Concentration, chlorination, and chemical analysis of drinking water for disinfection byproduct mixtures health effects research: US EPA’s four lab study. Environmental science & technology, 44(19), 7184-7192.

Regli, S., J. Chen, M. Messner, M. S. Elovitz, F. J. Letkiewicz, R. A. Pegram, T. J. Pepping, S. D. Richardson, and J. M. Wright. 2015. Estimating Potential Increased Bladder Cancer Risk Due to Increased Bromide Concentrations in Sources of Disinfected Drinking Waters. Environmental Science and Technology 49:13094–13102.

Richardson, S. D., M. J. Plewa, E. D. Wagner, R. Schoeny, and D. M. DeMarini. 2007. Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: A review and roadmap for research. Mutation Research – Reviews in Mutation Research 636:178–242.

Rivera-Utrilla, J., M. Sánchez-Polo, A. M. S. Polo, J. J. López-Peñalver, and M. V. López-Ramón. 2019. New technologies to remove halides from water: An overview. Pages 147–180 in R. Prasad and T. Karchiyappan, editors. Advanced Research in Nanosciences for Water Technology. Nanotechnology in the Life Sciences.

Springer, Cham. Rook, J. 1974. Formation of haloforms during chlorination. Water Treatment and Examination 28:234–243.

Sfynia, C. 2017. Minimisation of regulated and unregulated disinfection by-products in drinking water (PhD Thesis). Imperial College London.

Singer, P. C., and D. A. Reckhow. 2011. Chemical Oxidation. Page in J. Edzwald, editor. Water Quality and Treatment: A Handbook on Drinking Water. 6th edition. McGraw-Hill, New York.

Soltermann, F., C. Abegglen, C. Götz, and U. Von Gunten. 2016. Bromide Sources and Loads in Swiss Surface Waters and Their Relevance for Bromate Formation during Wastewater Ozonation. Environmental Science and Technology 50:9825–9834. Taylor, R. W. D. 1994. Methyl bromide-Is there any future for this noteworthy fumigant? Journal of Stored Products Research 30:253–260.

Thomas, V. M., J. A. Bedford, and R. J. Cicerone. 1997. Bromine emissions from leaded gasoline. Geophysical Research Letters 24:1371–1374.

Vainikka, P., and M. Hupa. 2012. Review on bromine in solid fuels – Part 2: Anthropogenic occurrence. Fuel 94:34–51.

Valero, F., and R. Arbós. 2010. Desalination of brackish river water using Electrodialysis Reversal (EDR). Control of the THMs formation in the Barcelona (NE Spain) area. Desalination 253:170–174.

VanBriesen, J. M. 2014. Potential drinking water effects of bromide discharges from coal-fired electric power plants. EPA NPDES Comments:1–38.

Ventura, F., & Rivera, J. (1985). Factors influencing the high content of brominated trihalomethanes in Barcelona’s water supply (Spain). Bulletin of environmental contamination and toxicology, 35(1), 73-81.

Villanueva, C. M., Cantor, K. P., Cordier, S., Jaakkola, J. J., King, W. D., Lynch, C. F., … & Kogevinas, M. (2004). Disinfection byproducts and bladder cancer: a pooled analysis. Epidemiology, 15(3), 357-367.

Villanueva, C. M., S. Cordier, L. Font-Ribera, L. A. Salas, and P. Levallois. 2015. Overview of Disinfection By-products and Associated Health Effects. Current environmental health reports 2:107–115.

Villanueva, C. M., Fernandez, F., Malats, N., Grimalt, J. O., & Kogevinas, M. (2003). Meta-analysis of studies on individual consumption of chlorinated drinking water and bladder cancer. Journal of Epidemiology & Community Health, 57(3), 166-173.

WHO. 2009. Bromide in drinking water: Background document for development of WHO Guidelines for Drinking-water Quality. World Health, Geneva, Switzerland.

WHO. 2018. Alternative drinking-water disinfectants: Bromine, iodine and silver. World Health Organization, Geneva, Switzerland.

Winid, B. 2015. Bromine and water quality – Selected aspects and future perspectives. Applied Geochemistry 63:413–435.

Yang, Y., Y. Komaki, S. Y. Kimura, H. Y. Hu, E. D. Wagner, B. J. Mariñas, and M. J. Plewa. 2014. Toxic impact of bromide and iodide on drinking water disinfected with chlorine or chloramines. Environmental Science and Technology 48:12362–12369

This information was prepared by faculty and students from the University of Georgia as part of a research program funded by the SFY2017 Regional Water Plan Seed Grant, “Bromide Concentrations in Surface Drinking Water Sources for Butts County” funded through the Georgia Environmental Protection Division.