What are Disinfection Byproducts (DBPs) in Drinking Water?

In order to control the presence of micro-organisms in public water supplies, most municipalities and water districts add a disinfectant to tap water before it goes into the distribution system. The most commonly used disinfectants for this purpose are chlorine, chlorine dioxide, chloramine (chlorine plus ammonia) and ozone.

These disinfectants are powerful oxidizing agents that react with any organic material present in the water to which they have been applied. These reactions cause the formation of new chemical compounds that are called disinfection byproducts (DBPs).

Only 9 out of hundreds of known disinfection byproducts are regulated.

Science is now aware of more than 700 disinfection byproducts. Many are known to be toxic.
Only 9 of these DBPs are currently regulated.

The 9 regulated DBPs are byproducts of chlorination. They are 4 triaholmethanes (THMs) and 5 haloacetic acids (HAAs). There are many other known, yet unregulated chlorination byproducts, such as Mutagen X.

Mutagen X: an unregulated byproduct of chlorination

Mutagen X is most likely to occur in water disinfected with chlorine dioxide. Studies indicate that it is toxic to the liver and kidneys, a possible carcinogen and potentially damaging to DNA.

It is becoming increasingly apparent that the toxic effects of many unregulated DBPs are more severe than the 9 regulated DBPs.

Disinfection byproducts are associated with cancers and birth defects.

Studies indicate probable links between exposure to disinfection byproducts in drinking water with various cancers and birth defects.

These compounds trigger the production of free radicals in the body causing cell damage. In addition to being probable carcinogens, they are linked to reproductive problems and mutations by altering DNA. They also suppress immune system function.

Bromine forms disinfection byproducts.

Bromine is a disinfectant commonly used for hot tubs.
Bromine also forms DBPs.

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References

Genotoxicity Assessment of Drinking Water Disinfection Byproducts by DNA Damage and Repair Pathway Profiling Analysis.
Lan J, Rahman SM, Gou N, Jiang T, Plewa MJ, Alshawabkeh A, Gu AZ
Environ Sci Technol. 2018
https://www.ncbi.nlm.nih.gov/pubmed/29660283

Disinfection By-Products: Formation and Occurrence of Drinking Water.
Richardson, Susan D. (2011).
In Nriagu, J.O. (ed.). Encyclopedia of Environmental Health. 2. Burlington Elsevier. pp. 110–13.
https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NERL&dirEntryId=189106

Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: A review and roadmap for research.
Richardson, Susan D.; Plewa, Michael J.; Wagner, Elizabeth D.; Schoeny, Rita; DeMarini, David M. (2007).
Mutation Research/Reviews in Mutation Research. 636 (1–3): 178–242.
https://www.ncbi.nlm.nih.gov/pubmed/17980649

Chlorination, Disinfection Byproducts in Drinking Water and Congenital Anomalies: Review and Meta-Analyses.
Nieuwenhuijsen, Mark; Martinez, David; Grellier, James; Bennett, James; Best, Nicky; Iszatt, Nina; Vrijheid, Martine; Toledano, Mireille B. (2009).
Environmental Health Perspectives. 117 (10): 1486–93.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2790500/ 

Bladder Cancer and Exposure to Water Disinfection By-Products through Ingestion, Bathing, Showering, and Swimming in Pools.
Villanueva, C. M.; Cantor, K. P.; Grimalt, J. O.; Malats, N.; Silverman, D.; Tardon, A.; Garcia-Closas, R.; Serra, C.; et al. (2006). " American Journal of Epidemiology. 165 (2): 148–56.https://www.ncbi.nlm.nih.gov/pubmed/17079692

The Occurrence of Disinfection By-Products (DBPs) of Health Concern in Drinking Water: Results of a Nationwide DBP Occurrence Study
EPA Study (2002)
https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=30002JEM.PDF