Cancer Causes & Control

, Volume 8, Issue 2, pp 192–200 | Cite as

Drinking water chlorination and cancer – a historical cohort study in Finland

  • Meri Koivusalo
  • Eero Pukkala
  • Terttu Vartiainen
  • Jouni J.K. Jaakkola
  • Timo Hakulinen


Chlorinationof water richin organic material is knownto produce a complexmixture of organochlorine compounds, including mutagenic and carcinogenicsubstances. A historical cohort study of 621,431 persons living in 56 townsin Finland was conducted in order to assess the relation between historicalexposure to drinking water mutagenicity and cancer. Exposure to quantity ofmutagenicity was calculated on the basis of historical information of rawwater quality and water treatment practices using an empirical equationrelating mutagenicity and raw water pH, KMnO4 value andchlorine dose. Cancercases were derived fromthe population-based FinnishCancer Registryandfollow-up time in the study started in 1970. Age, gender, time period,social class, and urban residence were taken into account in Poissonregression analysis of the observed numbers of cases using expected numbersof cases standardized for age and gender as a basis. Excess risks werecalculated using a continuous variab le for mutagenicity for 3,000 net rev/lexposure representing an average exposure in a town using chlorinated surfacewater. After adjustment for con-founding, a statistically significant excessrisk was observed for women in cancers of the bladder (relative risk [RR] =1.48, 95 percent confidence interval [CI] = 1.01-2.18), rectum (RR = 1.38, CI= 1.03-1.85), esophagus (RR = 1.90, CI = 1.02-3.52), and breast (RR = 1.11,CI = 1.01-1.22). These results support the magnitude of excess risks forrectal and bladder cancers found in earlier epidemiologic studies onchlorination by-products and give additional information on exposure-responseconcerning the mutagenic compounds. Nevertheless, due to the public healthimportance of water chlorination, uncertainty related to the magnitude ofobserved risks, and the fact that excess risks were observed only for women,the results of the study should be interpreted withcaution.

Chlorination Finland neoplasms water supply 


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Copyright information

© Chapman and Hall 1997

Authors and Affiliations

  • Meri Koivusalo
    • 1
  • Eero Pukkala
    • 1
  • Terttu Vartiainen
    • 2
  • Jouni J.K. Jaakkola
    • 3
  • Timo Hakulinen
    • 4
  1. 1.Finnish Cancer Registry CAHelsinkiFinland
  2. 2.Department of Environmental SciencesUniversity of Kuopio CAKuopioFinland
  3. 3.Department of Public Health CAHelsinkiFinland
  4. 4.Department of Cancer EpidemiologyKarolinska InstituteSweden

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