top of page


AKA - Chlorine By-products


Note: Unlike Fluoride, which enters the body only through ingestion, Chlorine and Chlorination by-products, aka, Trihalomethanes (THM's) enter the body by ingestion, and through skin absorption, and respiration during baths and showers making accumulative levels extremely difficult to measure.

Re: Government of Canada

Health Canada has established a guideline for THMs of 0.1 milligrams per litre. The cancer risk at this level over a lifetime is considered extremely low. The guidelines for THMs and other chlorination by-products are currently under review by a task group whose work is coordinated by Health Canada.

Re: Other Credible Studies

. 2004 Mar;15(2):179-86. doi: 10.1097/01.ede.0000112209.47765.d9.

Trihalomethanes in public water supplies and risk of stillbirth

Linda Dodds 1Will KingAlexander C AllenB Anthony ArmsonDeshayne B FellCarl Nimrod


PMID: 15127910 DOI: 10.1097/01.ede.0000112209.47765.d9


Background: The chlorine used to disinfect public drinking water supplies reacts with naturally occurring organic matter to form a number of chemical byproducts. Recent studies have implicated exposure to chlorination byproducts in drinking water, trihalomethanes (THMs), in particular, with intrauterine death.

Methods: We conducted a population-based case-control study in Nova Scotia and Eastern Ontario, Canada, to examine the effect of exposure to THMs on stillbirth risk. Cases were women who had a stillborn infant, and controls were a random sample of women with live births. Subjects were interviewed, and women with a public water source provided a residential water sample. Risks were examined according to residential THM level in tap water and to a total exposure metric incorporating tap water ingestion, showering, and bathing.

Results: We enrolled 112 stillbirth cases and 398 live birth controls. Women with a residential total THM level of 80 or more microg/L had twice the risk of a stillbirth compared with women with no exposure to THMs (adjusted odds ratio [OR] = 2.2; 95% confidence interval [CI] = 1.1-4.4). The highest quintile of total THM exposure using the total exposure metric was associated with an adjusted odds ratio of 2.4 (95% CI = 1.2-4.6) compared with women not exposed to THMs. Similar results were seen for specific THM compounds. A monotonic dose-response relationship was not seen.

Conclusions: Our results provide evidence for an increased risk of stillbirth associated with exposure to chlorination byproducts through ingestion and showering and bathing, although there was not a clear dose-response relationship.

Similar articles

Relation between stillbirth and specific chlorination by-products in public water supplies.

King WD, Dodds L, Allen AC.

Environ Health Perspect. 2000 Sep;108(9):883-6. doi: 10.1289/ehp.00108883.

PMID: 11017894 Free PMC article.

Colorectal Cancer and Long-Term Exposure to Trihalomethanes in Drinking Water: A Multicenter Case-Control Study in Spain and Italy.

Villanueva CM, Gracia-Lavedan E, Bosetti C, Righi E, Molina AJ, Martín V, Boldo E, Aragonés N, Perez-Gomez B, Pollan M, Acebo IG, Altzibar JM, Zabala AJ, Ardanaz E, Peiró R, Tardón A, Chirlaque MD, Tavani A, Polesel J, Serraino D, Pisa F, Castaño-Vinyals G, Espinosa A, Espejo-Herrera N, Palau M, Moreno V, La Vecchia C, Aggazzotti G, Nieuwenhuijsen MJ, Kogevinas M.

Environ Health Perspect. 2017 Jan;125(1):56-65. doi: 10.1289/EHP155. Epub 2016 Jul 6.

PMID: 27383820 Free PMC article.

Exposure assessment in epidemiologic studies of adverse pregnancy outcomes and disinfection byproducts.

King WD, Dodds L, Armson BA, Allen AC, Fell DB, Nimrod C.

J Expo Anal Environ Epidemiol. 2004 Nov;14(6):466-72. doi: 10.1038/sj.jea.7500345.

PMID: 15026776

Chlorination disinfection byproducts in water and their association with adverse reproductive outcomes: a review.

Nieuwenhuijsen MJ, Toledano MB, Eaton NE, Fawell J, Elliott P.

Occup Environ Med. 2000 Feb;57(2):73-85. doi: 10.1136/oem.57.2.73.

PMID: 10711274 Free PMC article. Review.

Chlorination byproducts, their toxicodynamics and removal from drinking water.

Gopal K, Tripathy SS, Bersillon JL, Dubey SP.

J Hazard Mater. 2007 Feb 9;140(1-2):1-6. doi: 10.1016/j.jhazmat.2006.10.063. Epub 2006 Oct 27.

PMID: 17129670 Review.

See all similar articles

Cited by 12 articles

Exposure to disinfectant by-products and the risk of stillbirth in Massachusetts.

Rivera-Núñez Z, Wright JM, Meyer A.

Occup Environ Med. 2018 Oct;75(10):742-751. doi: 10.1136/oemed-2017-104861. Epub 2018 Jul 30.

PMID: 30061312 Free PMC article.

Blood Biomarkers of Late Pregnancy Exposure to Trihalomethanes in Drinking Water and Fetal Growth Measures and Gestational Age in a Chinese Cohort.

Cao WC, Zeng Q, Luo Y, Chen HX, Miao DY, Li L, Cheng YH, Li M, Wang F, You L, Wang YX, Yang P, Lu WQ.

Environ Health Perspect. 2016 Apr;124(4):536-41. doi: 10.1289/ehp.1409234. Epub 2015 Aug 18.

PMID: 26340795 Free PMC article.

Validation of drinking water disinfection by-product exposure assessment for rural areas in the National Children's Study.

Binkley TL, Thiex NW, Specker BL.

J Expo Sci Environ Epidemiol. 2015 May;25(3):303-7. doi: 10.1038/jes.2014.51. Epub 2014 Jul 16.

PMID: 25027449

Predictive model for chloroform during disinfection of water for consumption, city of Montevideo.

Gomez Camponovo M, Seoane Muniz G, Rothenberg SJ, Umpiérrez Vazquez E, Achkar Borras M.

Environ Monit Assess. 2014 Oct;186(10):6711-9. doi: 10.1007/s10661-014-3884-5. Epub 2014 Jul 1.

PMID: 24981876

Risk of stillbirth in the relation to water disinfection by-products: a population-based case-control study in Taiwan.

Hwang BF, Jaakkola JJ.

PLoS One. 2012;7(3):e33949. doi: 10.1371/journal.pone.0033949. Epub 2012 Mar 23.

PMID: 22457804 Free PMC article.

See all "Cited by" articles

bottom of page