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Important Facts for Drinking Water: Disinfection Byproducts


A community water system is a public water system which serves at least 15 service connections used by year-round residents or regularly serves at least 25 year-round residents.


Number of persons served.



Data Interpretation Issues

Analyte data are not obtained for every system in every time period.

Why Is This Important?

People drink and use water every day. The majority of Americans are provided with high quality drinking water. About 90% of people in the U.S. (262 million in 2006) get their water from a community water system versus a smaller water supply such as a household well. The U.S. Environmental Protection Agency (EPA) sets regulations for treating and monitoring drinking water delivered by community water systems. Currently, there are water quality standards and monitoring requirements for over 90 contaminants. Drinking water protection programs play a critical role in ensuring high quality drinking water and in protecting the public's health.

Because people drink and use water every day, contaminants in drinking water have the potential to affect many people. The number of people served by a community water system varies from at least 25 people to hundreds of thousands. Community water systems in the U.S. provide among the highest quality drinking water in the world. However, some contaminants are present at low levels, and it is still possible that drinking water can become contaminated at higher levels. If a person is exposed to a high enough level of a contaminant, they may become ill. Effects can be seen by the duration (time) of the exposure. Short-term or long-term effects depend on the specific contaminant, the level of contaminant in the water, and the person's individual susceptibility. As additional information is obtained about how specific contaminants affect public health, standards may change in order to better protect public health.

In order to ensure the public's safety with regards to drinking water, community water suppliers treat their water with several products including: chlorine, ozone, chlorine dioxide, ultraviolet light, etc. These products that are used to kill pathogens, however, sometimes react with naturally-occurring organic matter, and create disinfection byproducts. Disinfection byproducts for which the EPA has created standards include: total trihalomethanes (TTHM), haloacetic acids (HAA5), bromate, and chlorite. Although the risk of illness from drinking water that has not been disinfected is much higher than illness from disinfection byproducts, some increased health risks do occur from consumption of disinfection byproducts. Consumption (through inhalation, ingestion, and through the skin) at high levels over a long period of time has been shown to increase the risk of developing bladder cancer. Rectal and colon cancer along with problems involving the liver, kidney, and nervous system have also been shown to have a correlation with those who have been exposed to disinfection byproducts over a long period of time.

The information provided above is from the Utah Department of Health's Center for Health Data IBIS-PH web site ( The information published on this website may be reproduced without permission. Please use the following citation: "Retrieved Wed, 23 April 2014 17:06:41 from Utah Department of Health, Center for Health Data, Indicator-Based Information System for Public Health Web site:".

Content updated: Tue, 19 Nov 2013 23:09:25 MST