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Massachusetts Department of Public Health seal Massachusetts Environmental Public Health Tracking

Disinfection Byproducts

Before it is treated, public drinking water may contain viruses and bacteria that can cause illness, such as gastrointestinal disorders or diarrhea. Public water suppliers disinfect drinking water to kill these viruses and bacteria. Chlorine is the most commonly used disinfectant, sometimes used with other disinfectants, such as ozone, chloramine, chlorine dioxide, and ultraviolet light.

Did You Know?
Some Community Water Systems use monochloramine as a primary or secondary drinking water disinfectant instead of chlorine, which may produce fewer of the type of DBPs which are regulated.

Disinfection byproducts (DBPs) are a family of chemicals that include Total Trihalomethanes and Haloacetic Acids. DBPs are formed when chlorine-based disinfectants react with naturally occurring organic matter and other substances in the source water. The levels of DBPs depend upon the nature of the source water, the type of treatment to remove particles and organic matter, and the type and concentration of disinfectant.

The risk of illness from DBPs is much lower than the risk of illness from drinking most surface water and some groundwater sources that have not been disinfected. The major health risks from DBPs are from long-term exposures.

When people consume water containing high levels of DBPs over many years, their risk of developing bladder cancer increases. Other health effects that may be associated with exposure to DBPs include rectal and colon cancer. Adverse developmental and reproductive effects associated with exposure to DBPs during pregnancy are a concern. These links have been studied with mixed results; however, the weight of evidence of the health effects data suggests a potential association.

Data Considerations

When reviewing and interpreting drinking water disinfection byproducts data, it is important to take into consideration the following:

  • The data presented are for public water systems only. Residents may have exposure to disinfection byproducts from private well water.
  • Exposure to disinfection byproducts in drinking water depends upon the concentration of disinfection byproducts in the drinking water and the amount of water consumed by the individual. Water consumption varies by such factors as climate and level of physical activity.
  • Many factors can affect whether exposure can lead to a health problem, including level of contamination, amount of water consumed, and the length of time water was contaminated. Some populations may be more susceptible to health problems following exposure, such as pregnant woman, children, and immune suppressed individuals.
  • This website provides a summary of drinking water violations by community. Consumer Confidence Reports on public drinking water quality are required to be provided annually to consumers. Your Community Water System should be contacted for this report, which will provide more detailed information on any specific water system violations.
  • Community Water Systems (CWSs) can serve areas substantially beyond the boundaries of the principal city/town served.
  • Multiple CWSs can serve the same city/town and multiple cities/towns can be served by a single.
  • For a list of all Massachusetts Community Water Systems and communities served, click here (pdf).

For additional information, please read the FAQ.

Available Data on Water Quality Measures for Disinfection Byproducts

Click the Explore Maps & Tables link button on this page to access the following measures for disinfection byproducts in your community. The most current available data will be shown. Be sure to check the site periodically as new data are added each year.

To protect privacy, no information is shown that could identify an individual home or family.

  • Maximum disinfection byproduct concentrations by number of Community Water Systems and year of testing.
  • Mean disinfection byproduct concentrations by number of Community Water Systems and year of testing
  • Maximum disinfection byproduct concentrations by number of people served by the Community Water Systems and year of testing
  • Mean disinfection byproduct concentrations by number of people served by the Community Water Systems and year of testing
  • Mean disinfection byproduct concentrations by individual Community Water System or county and year of testing
  • Drinking water violations by Community Water System or community and year of violation

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