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Environmental Assessment

Exposures and Internal Doses of Trihalomethanes in Humans: Multi-Route Contributions from Drinking Water (Final)

Report Information

The National Center for Environmental Assessment (NCEA) has released a final report that presents and applies a method to estimate distributions of internal concentrations of trihalomethanes (THMs) in humans resulting from a residential drinking water exposure. The report presents simulations of oral, dermal and inhalation exposures and demonstrates the feasibility of linking the US EPA’s information Collection Rule database with other databases on external exposure factors and physiologically based pharmacokinetic modeling to refine population-based estimates of exposure.

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John C. Lipscomb
  • by phone at:   513-569-7217
  • by fax at:   513-487-2539
  • by email at:  lipscomb.john@epa.gov


This final report, Exposures and Internal Doses of Trihalomethanes in Humans: Multi-Route Contributions from Drinking Water, presents the results of an analysis in which multiple data sets and physiologically based pharmacokinetic models were combined to estimate the oral, dermal and inhalation route-specific contributions to internal doses of THMs, which are drinking water disinfection byproducts. It was supported by a contract to Wilkes Technologies, Inc. (Bethesda, MD). Point estimates of THM concentrations were taken from the Agency’s Information Collection Rule database; additional databases on external exposure factors, e.g. water use, household behaviors, human activity patterns, house volume and ventilation provided distributions of exposure data. The results demonstrated that the inhalation exposure pathway represents a significant contribution to THM internal doses.

Topics covered include:
  • Data Quality and Assumptions
  • Modeling and Integration Framework: concentrations of THMs in drinking water, water use patterns, human in-home behavioral characteristics, room volumes and ventilation, physiologically based pharmacokinetic modeling.
  • Required Data.
  • Population distributions of internal doses in the adult male, adult female and 6 year old child resulting from household contact with drinking water.
  • Contributions of oral, dermal and inhalation routes to attained internal concentrations of THMs.


Jun 2003Feasibility document published.
Sep 2003Simplified acquisition awarded to Wilkes Technologies, Inc.
Jan 2004Contractor report received.
Sep 2004Peer review contract established.
Mar 2005Internal Agency Review completed.
Jun 2005External Panel Review of final report reviewed.
Dec 2005Simplified acquisition developed to refine the description of the model and documentation of parameter values.
Nov 2006EPA Releases the final report.

Next Steps

This is the final document. Results will be published in the peer reviewed literature.

Additional Information

There are equations in this document that were not converted to a 508-compliant format, should anyone want more information regarding any of these equations please address these questions to the contact on the website.


U.S. EPA. Exposures and Internal Doses of Trihalomethanes in Humans: Multi-Route Contributions from Drinking Water (Final). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-06/087, 2006.


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