Disinfection by-product

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Disinfection by-products (DBPs) are organic and inorganic compounds resulting from chemical reactions between organic and inorganic substances such as contaminates and chemical treatment disinfection agents, respectively, in water during water disinfection processes. [1]

Contents

Chlorination disinfection byproducts

Chlorinated disinfection agents such as chlorine and monochloramine 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 DBPs. [1]

Occurrence

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]

In 2021, a new group of DBPs known as halogenated pyridinols was discovered, containing at least 8 previously unknown heterocyclic nitrogenous DBPs. They were found to require low pH treatments of 3.0 to be removed effectively. When their developmental and acute toxicity was tested on zebrafish embryos, it found to be slightly lower than those of halogenated benzoquinones, but dozens of times higher than of commonly known DBPs such as tribromomethane and iodoacetic acid. [9]

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 [10] [11] and for babies being born small for gestational age, [12] but not for congenital anomalies (birth defects). [13] Early-term miscarriages have also been reported in some studies. [14] [15] 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". [16]

Regulation and monitoring

The United States Environmental Protection Agency has set Maximum Contaminant Levels (MCLs) for bromate, chlorite, haloacetic acids and total trihalomethanes (TTHMs). [17] 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. [18] 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. [19]

See also

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Chloroform, or trichloromethane, is an organic compound with the formula CHCl3 and a common solvent. It is a very volatile, colorless, strong-smelling, dense liquid produced on a large scale as a precursor to PTFE and refrigerants and is a trihalomethane that serves as a powerful anesthetic, euphoriant, anxiolytic, and sedative when inhaled or ingested. Chloroform was used as an anesthetic between the 19th century and the first half of the 20th century. Chloroform is miscible with many solvents but it is only very slightly soluble in water.

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<span class="mw-page-title-main">Sodium hypochlorite</span> Chemical compound (known in solution as bleach)

Sodium hypochlorite, commonly known in a dilute solution as (chlorine) bleach, is an inorganic chemical compound with the formula NaOCl, consisting of a sodium cation and a hypochlorite anion. It may also be viewed as the sodium salt of hypochlorous acid. The anhydrous compound is unstable and may decompose explosively. It can be crystallized as a pentahydrate NaOCl·5H
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<span class="mw-page-title-main">Disinfectant</span> Antimicrobial agent that inactivates or destroys microbes

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<span class="mw-page-title-main">Iodoacetic acid</span> Chemical compound

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<span class="mw-page-title-main">Bleach</span> Chemicals used to whiten or disinfect

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<span class="mw-page-title-main">Water chlorination</span> Chorination of water

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<span class="mw-page-title-main">Chlorine-releasing compounds</span>

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<span class="mw-page-title-main">Stuart W. Krasner</span>

Stuart William Krasner, 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.

References

  1. 1 2 3 4 5 6 7 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. 1 2 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. Bibcode:2008EnST...42.8330R. doi:10.1021/es801169k. PMID   19068814.
  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. S2CID   10366131.
  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. S2CID   23293533.
  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. Bibcode:2010EnST...44.3205L. doi:10.1021/es903241k. PMID   20222731.
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  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. Bibcode:2008EnST...42..955P. doi:10.1021/es071754h. PMID   18323128.
  9. ↑ Haiyang Tang (2021). "A New Group of Heterocyclic Nitrogenous Disinfection Byproducts (DBPs) in Drinking Water: Role of Extraction pH in Unknown DBP Exploration". Environmental Science & Technology. 55 (10): 6764–6772. Bibcode:2021EnST...55.6764T. doi:10.1021/acs.est.1c00078. PMID   33928775. S2CID   233460007.
  10. ↑ 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.
  11. ↑ 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. S2CID   28757535.
  12. ↑ 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. S2CID   25361080.
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  14. ↑ 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. S2CID   35312352.
  15. ↑ 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.
  16. ↑ "Disinfectants and Disinfection By-Products Session Objectives" [Water Sanitation Health (WSH)](PDF). World Health Organization (WHO).
  17. ↑ "Drinking Water Contaminants". United States Environmental Protection Agency (EPA). 21 September 2015.
  18. ↑ Directive 98/83/EC of 3 November 1998 of the European Parliament and of the Council on the quality of water intended for human consumption
  19. ↑ "Guidelines for Drinking-water Quality" [Water Sanitation Health (WSH)](PDF). Geneva: World Health Organization (WHO). 2008.
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