Disinfection by-product

Disinfection by-products (DBPs) result from chemical reactions between organic and inorganic matter in water with chemical treatment agents during the water disinfection process.[1]

Chlorination disinfection byproducts

Chlorinated disinfection agents such as chlorine and chloramine are strong oxidizing agents introduced into water in order to destroy pathogenic microbes, to oxidize taste/odor-forming compounds, and to form a disinfectant residual so water can reach the consumer tap safe from microbial contamination. These disinfectants may react with naturally present fulvic and humic acids, amino acids, and other natural organic matter, as well as iodide and bromide ions, to produce a range of DBPs such as the trihalomethanes (THMs), haloacetic acids (HAAs), bromate, and chlorite (which are regulated in the US), and so-called "emerging" DBPs such as halonitromethanes, haloacetonitriles, haloamides, halofuranones, iodo-acids such as iodoacetic acid, iodo-THMs (iodotrihalomethanes), nitrosamines, and others.[1]

Chloramine has become a popular disinfectant in the US, and it has been found to produce N-nitrosodimethylamine (NDMA), which is a possible human carcinogen, as well as highly genotoxic iodinated DBPs, such as iodoacetic acid, when iodide is present in source waters.[1][2]

Residual chlorine and other disinfectants may also react further within the distribution network — both by further reactions with dissolved natural organic matter and with biofilms present in the pipes. In addition to being highly influenced by the types of organic and inorganic matter in the source water, the different species and concentrations of DBPs vary according to the type of disinfectant used, the dose of disinfectant, the concentration of natural organic matter and bromide/iodide, the time since dosing (i.e. water age), temperature, and pH of the water.[3]

Swimming pools using chlorine have been found to contain trihalomethanes, although generally they are below current EU standard for drinking water (100 micrograms per litre).[4] Concentrations of trihalomethanes (mainly chloroform) of up to 0.43 ppm have been measured.[5] In addition, trichloramine has been detected in the air above swimming pools,[6] and it is suspected in the increased asthma observed in elite swimmers. Trichloramine is formed by the reaction of urea (from urine and sweat) with chlorine and gives the indoor swimming pool its distinctive odor.

Byproducts from non-chlorinated disinfectants

Several powerful oxidizing agents are used in disinfecting and treating drinking water, and many of these also cause the formation of DBPs. Ozone, for example, produces ketones, carboxylic acids, and aldehydes, including formaldehyde. Bromide in source waters can be converted by ozone into bromate, a potent carcinogen that is regulated in the United States, as well as other brominated DBPs.[1]

As regulations are tightened on established DBPs such as THMs and HAAs, drinking water treatment plants may switch to alternative disinfection methods. This change will alter the distribution of classes of DBP's.[1]


DBPs are present in most drinking water supplies that have been subject to chlorination, chloramination, ozonation, or treatment with chlorine dioxide. Many hundreds of DBPs exist in treated drinking water and at least 600 have been identified.[1][7] The low levels of many of these DBPs, coupled with the analytical costs in testing water samples for them, means that in practice only a handful of DBPs are actually monitored. Increasingly it is recognized that the genotoxicities and cytotoxicities of many of the DBPs not subject to regulatory monitoring, (particularly iodinated, nitrogenous DBPs) are comparatively much higher than those DBPs commonly monitored in the developed world (THMs and HAAs).[1][2][8]

Health effects

Epidemiological studies have looked at the associations between exposure to DBPs in drinking water with cancers, adverse birth outcomes and birth defects. Meta-analyses and pooled analyses of these studies have demonstrated consistent associations for bladder cancer[9][10] and for babies being born small for gestational age,[11] but not for congenital anomalies (birth defects).[12] Early-term miscarriages have also been reported in some studies.[13][14] The exact putative agent remains unknown, however, in the epidemiological studies since the number of DBPs in a water sample are high and exposure surrogates such as monitoring data of a specific by-product (often total trihalomethanes) are used in lieu of more detailed exposure assessment. The World Health Organization has stated that "the risk of death from pathogens is at least 100 to 1000 times greater than the risk of cancer from disinfection by-products (DBPs)" {and} the "risk of illness from pathogens is at least 10 000 to 1 million times greater than the risk of cancer from DBPs".[15]

Regulation and monitoring

The United States Environmental Protection Agency has set Maximum Contaminant Levels (MCLs) for bromate, chlorite, haloacetic acids and total trihalomethanes (TTHMs).[16] In Europe, the level of TTHMs has been set at 100 micrograms per litre, and the level for bromate to 10 micrograms per litre, under the Drinking Water Directive.[17] No guideline values have been set for HAAs in Europe. The World Health Organization has established guidelines for several DBPs, including bromate, bromodichloromethane, chlorate, chlorite, chloroacetic acid, chloroform, cyanogen chloride, dibromoacetonitrile, dibromochloromethane, dichloroacetic acid, dichloroacetonitrile, NDMA, and trichloroacetic acid.[18]

See also


  1. ^ a b c d e f g Richardson, Susan D.; Plewa, Michael J.; Wagner, Elizabeth D.; Schoeny, Rita; DeMarini, David M. (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 (1–3): 178–242. doi:10.1016/j.mrrev.2007.09.001. PMID 17980649.
  2. ^ a b Richardson, Susan D.; Fasano, Francesca; Ellington, J. Jackson; Crumley, F. Gene; Buettner, Katherine M.; Evans, John J.; Blount, Benjamin C.; Silva, Lalith K.; et al. (2008). "Occurrence and Mammalian Cell Toxicity of Iodinated Disinfection Byproducts in Drinking Water". Environmental Science & Technology. 42 (22): 8330–8338. doi:10.1021/es801169k.
  3. ^ Koivusalo,, Meri; Vartiainen, Terttu (1997). "Drinking Water Chlorination By-Products And Cancer". Reviews on Environmental Health. 12 (2): 81–90. doi:10.1515/REVEH.1997.12.2.81. PMID 9273924.
  4. ^ Nieuwenhuijsen, Mark J.; Toledano, Mireille B.; Elliott, Paul (2000). "Uptake of chlorination disinfection by-products; a review and a discussion of its implications for exposure assessment in epidemiological studies". Journal of Exposure Analysis and Environmental Epidemiology. 10 (6): 586–99. doi:10.1038/sj.jea.7500139. PMID 11140442.
  5. ^ Beech, J. Alan; Diaz, Raymond; Ordaz, Cesar; Palomeque, Besteiro (January 1980). "Nitrates, chlorates and trihalomethanes in swimming pool water". American Journal of Public Health. 70 (1): 79–82. doi:10.2105/AJPH.70.1.79. PMC 1619346. PMID 7350831.
  6. ^ LaKind, Judy S.; Richardson, Susan D.; Blount, Benjamin C. (2010). "The Good, the Bad, and the Volatile: Can We Have Both Healthy Pools and Healthy People?". Environmental Science & Technology. 44 (9): 3205–3210. doi:10.1021/es903241k.
  7. ^ Richardson, Susan D. (2011). "Disinfection By-Products: Formation and Occurrence of Drinking Water". In Nriagu, J.O. Encyclopedia of Environmental Health. 2. Burlington Elsevier. pp. 110–13. ISBN 978-0-444-52273-3.
  8. ^ Plewa, Michael J.; Muellner, Mark G.; Richardson, Susan D.; Fasano, Francesca; Buettner, Katherine M.; Woo, Yin-Tak; McKague, A. Bruce; Wagner, Elizabeth D. (2008). "Occurrence, Synthesis, and Mammalian Cell Cytotoxicity and Genotoxicity of Haloacetamides: An Emerging Class of Nitrogenous Drinking Water Disinfection Byproducts". Environmental Science & Technology. 42 (3): 955–61. doi:10.1021/es071754h.
  9. ^ Villanueva, C. M.; Cantor, K. P.; Grimalt, J. O.; Malats, N.; Silverman, D.; Tardon, A.; Garcia-Closas, R.; Serra, C.; et al. (2006). "Bladder Cancer and Exposure to Water Disinfection By-Products through Ingestion, Bathing, Showering, and Swimming in Pools". American Journal of Epidemiology. 165 (2): 148–56. doi:10.1093/aje/kwj364. PMID 17079692.
  10. ^ Costet, N.; Villanueva, C. M.; Jaakkola, J. J. K.; Kogevinas, M.; Cantor, K. P.; King, W. D.; Lynch, C. F.; Nieuwenhuijsen, M. J.; 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): 379–85. doi:10.1136/oem.2010.062703. PMID 21389011.
  11. ^ Grellier, James; Bennett, James; Patelarou, Evridiki; Smith, Rachel B.; Toledano, Mireille B.; Rushton, Lesley; Briggs, David J.; Nieuwenhuijsen, Mark J. (2010). "Exposure to Disinfection By-products, Fetal Growth, and Prematurity". Epidemiology. 21 (3): 300–13. doi:10.1097/EDE.0b013e3181d61ffd. PMID 20375841.
  12. ^ Nieuwenhuijsen, Mark; Martinez, David; Grellier, James; Bennett, James; Best, Nicky; Iszatt, Nina; Vrijheid, Martine; Toledano, Mireille B. (2009). "Chlorination, Disinfection Byproducts in Drinking Water and Congenital Anomalies: Review and Meta-Analyses". Environmental Health Perspectives. 117 (10): 1486–93. doi:10.1289/ehp.0900677. PMC 2790500. PMID 20019896.
  13. ^ Waller, Kirsten; Swan, Shanna H.; DeLorenze, Gerald; Hopkins, Barbara (1998). "Trihalomethanes in drinking water and spontaneous abortion". Epidemiology. 9 (2): 134–140. doi:10.1097/00001648-199803000-00006. PMID 9504280.
  14. ^ Savitz, David A.; Singer, Philip C.; Hartmann, Katherine E.; Herring, Amy H.; Weinberg, Howard S.; Makarushka, Christina; Hoffman, Caroline; Chan, Ronna; MacLehose, Richard (2005). "Drinking Water Disinfection By-Products and Pregnancy Outcome" (PDF). Denver, CO: Awwa Research Foundation.
  15. ^ "Disinfectants and Disinfection By-Products Session Objectives" [Water Sanitation Health (WSH)] (PDF). World Health Organization (WHO).
  16. ^ "Drinking Water Contaminants". United States Environmental Protection Agency (EPA).
  17. ^ "Directive 83". 3 November 1998. on the quality of water intended for human consumption
  18. ^ "Guidelines for Drinking-water Quality" [Water Sanitation Health (WSH)] (PDF). Geneva: World Health Organization (WHO). 2008.
David A. Savitz

David A. Savitz is a professor of Community Health in the Epidemiology Section of the Program in Public Health, Vice President for Research, and Professor of Obstetrics and Gynecology, at The Alpert Medical School of Brown University, and Associate Director for Perinatal Research in The Department of Obstetrics and Gynecology at Women & Infants Hospital, both in Providence, Rhode Island.

Savitz is the author of Interpreting epidemiologic evidence: strategies for study design and analysis (ISBN 0-19-510840-X) and more than 275 peer-reviewed articles. He was elected to the Institute of Medicine in 2007.

Drinking water quality legislation of the United States

In the United States, public drinking water is governed by the laws and regulations enacted by the federal and state governments. Certain ordinances may also be created at a more local level. The Safe Drinking Water Act (SDWA) is the principal federal law. The SDWA authorizes the United States Environmental Protection Agency (EPA) to create and enforce regulations to achieve the SDWA goals.

Green nanotechnology

Green nanotechnology refers to the use of nanotechnology to enhance the environmental sustainability of processes producing negative externalities. It also refers to the use of the products of nanotechnology to enhance sustainability. It includes making green nano-products and using nano-products in support of sustainability.

Green nanotechnology has been described as the development of clean technologies, "to minimize potential environmental and human health risks associated with the manufacture and use of nanotechnology products, and to encourage replacement of existing products with new nano-products that are more environmentally friendly throughout their lifecycle."

Iodoacetic acid

Iodoacetic acid is a derivative of acetic acid. It is a toxic compound, because, like many alkyl halides, it is an alkylating agent. It reacts with cysteine residues in proteins. It is often used to modify SH-groups to prevent the re-formation of disulfide bonds after the reduction of cystine residues to cysteine during protein sequencing.

Mutagen X

Mutagen X (MX), or 3-chloro-4-(dichloromethyl)-5-hydroxy-5H-furan-2-one, is a byproduct of the disinfection of water by chlorination. MX is produced by reaction of chlorine with natural humic acids.

MX is found in chlorinated drinking water all over the world and is an environmental carcinogen that is known to cause several types of cancer in rats when present in large enough concentrations. It is listed by the International Agency for Research on Cancer as a group 2B carcinogen meaning it is "possibly carcinogenic to humans". Although the concentration of MX in drinking water is typically 100- to 1000-fold lower than other common byproducts of water chlorination such as trihalomethanes, MX might play a role in the increased cancer risks that have been associated with the consumption of chlorinated water because of its potency in inducing DNA damage.


Nanofiltration (NF) is a relatively recent membrane filtration process used most often with low total dissolved solids water such as surface water and fresh groundwater, with the purpose of softening (polyvalent cation removal) and removal of disinfection by-product precursors such as natural organic matter and synthetic organic matter.Nanofiltration is also becoming more widely used in food processing applications such as dairy, for simultaneous concentration and partial (monovalent ion) demineralisation.

Reclaimed water

Reclaimed or recycled water (also called wastewater reuse or water reclamation) is the process of converting wastewater into water that can be reused for other purposes. Reuse may include irrigation of gardens and agricultural fields or replenishing surface water and groundwater (i.e., groundwater recharge). Reused water may also be directed toward fulfilling certain needs in residences (e.g. toilet flushing), businesses, and industry, and could even be treated to reach drinking water standards. This last option is called either "direct potable reuse" or "indirect potable" reuse, depending on the approach used. Colloquially, the term "toilet to tap" also refers to potable reuse.Reclaiming water for reuse applications instead of using freshwater supplies can be a water-saving measure. When used water is eventually discharged back into natural water sources, it can still have benefits to ecosystems, improving streamflow, nourishing plant life and recharging aquifers, as part of the natural water cycle.Wastewater reuse is a long-established practice used for irrigation, especially in arid countries. Reusing wastewater as part of sustainable water management allows water to remain as an alternative water source for human activities. This can reduce scarcity and alleviate pressures on groundwater and other natural water bodies.

Stuart W. Krasner

Stuart William Krasner (Born 1949), was the Principal Environmental Specialist (retired) with the Metropolitan Water District of Southern California, at the Water Quality Laboratory located in La Verne, California. In his 41 years with Metropolitan, he made revolutionary changes in the field's understanding of how disinfection by-products occur, are formed and how they can be controlled in drinking water. His research contributions include the study of emerging DBPs including those associated with chlorine, chloramines, ozone, chlorine dioxide and bromide/iodide-containing waters. He made groundbreaking advances in understanding the watershed sources of pharmaceuticals and personal care products (PPCPs) and wastewater impacts on drinking-water supplies. For DBPs and PPCPs, he developed analytical methods and occurrence data and he provided technical expertise for the development of regulations for these drinking water contaminants. In the early 1990s, Krasner developed the 3x3 matrix illustrating removal of total organic carbon from drinking water as a function of water alkalinity and initial total organic carbon concentration. The matrix was revised by him and included in the USEPA Stage 1 D/DBP regulation as the enhanced coagulation requirement. Every water utility in the U.S. that is subject to this regulation is required to meet total organic carbon removal requirements along with their exceptions.

He has been a key member of the toxicology and epidemiology community by providing key data for the development of improved carcinogen and non-carcinogen exposure assessments. In his early career at Metropolitan he developed key advances in the control of tastes and odors in drinking water including analytical methods, sensory analysis and determining sources and treatment of off-flavors.

UV filter

UV filters are individual compounds or mixtures that block or absorb ultraviolet (UV) light. UV filters are used in sunscreens to protect skin or in photography to reduce the level of ultraviolet light that strikes the recording medium. UV filters can undergo transformation into less protective or more toxic products. These transformation products can have health and environmental effects.

Urine-indicator dye

Urine-indicator dye is a substance which is supposed to be able to react with urine to form a coloured cloud in a swimming pool or hot tub, thus indicating the location of people who are urinating while they are in the water. A 2015 report from the National Swimming Pool Foundation called this "the most common pool myth of all time", with nearly half of Americans surveyed by researchers believing that the dye existed.Urine is difficult to detect as many of the naturally occurring compounds within urine are unstable and react freely with common disinfectants like chlorine, creating a large number of disinfection by-product (DBP) compounds from the original organic chemicals in urine. In an article published in 2000, Snopes confirmed such a dye did not exist. However a study published by the University of Alberta in 2017 identified urine in hot tubs and swimming pools based on other markers such as acesulfame potassium, used extensively as an artificial sweetener, being passed chemically unchanged in urine, and not suffering from DBP-related changes in water.Rumours of the origin of urine indicator-dye go back at least as far as 1958, and the story is commonly told to children by parents who do not wish them to urinate in the pool. A 1985 biography of Orson Welles describes him using such a dye as part of a prank in 1937.

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