Case study approach to modeling historical disinfection by-product exposure in Iowa drinking waters

Stuart W. Krasner*, Kenneth P. Cantor, Peter J. Weyer, Mariana Hildesheim, Gary Lee Amy

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


In the 1980s, a case–control epidemiologic study was conducted in Iowa (USA) to analyze the association between exposure to disinfection by-products (DBPs) and bladder cancer risk. Trihalomethanes (THMs), the most commonly measured and dominant class of DBPs in drinking water, served as a primary metric and surrogate for the full DBP mixture. Average THM exposure was calculated, based on rough estimates of past levels in Iowa. To reduce misclassification, a follow-up study was undertaken to improve estimates of past THM levels and to re-evaluate their association with cancer risk. In addition, the risk associated with haloacetic acids, another class of DBPs, was examined. In the original analysis, surface water treatment plants were assigned one of two possible THM levels depending on the point of chlorination. The re-assessment considered each utility treating surface or groundwater on a case-by-case basis. Multiple treatment/disinfection scenarios and water quality parameters were considered with actual DBP measurements to develop estimates of past levels. The highest annual average THM level in the re-analysis was 156 μg/L compared to 74 μg/L for the original analysis. This allowed the analysis of subjects exposed at higher levels (> 96 μg/L). The re-analysis established a new approach, based on case studies and an understanding of the water quality and operational parameters that impact DBP formation, for determining historical exposure.

Original languageEnglish (US)
Pages (from-to)183-190
Number of pages8
JournalJournal of Environmental Sciences
StatePublished - Aug 1 2017


  • Bladder cancer
  • Disinfection by-products
  • Epidemiology
  • Exposure assessment
  • Haloacetic acids
  • Trihalomethanes

ASJC Scopus subject areas

  • Environmental Engineering
  • General Environmental Science
  • Environmental Chemistry


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