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Community Drinking Water Contaminants

This Web site contains information about the levels of four contaminants in drinking water: nitrate, arsenic, disinfection by-products, and lead. These contaminants were selected for the Tracking Network because they occur more frequently in drinking water than other contaminants at levels that may be of public health significance. The data on these contaminants are not gathered specifically to assess the level of exposure or to track changes in water quality over time. However, these data are the only consistent drinking water quality data nationwide that are currently available for surveillance activities.

Arsenic: Arsenic is a toxic chemical element that is naturally found in the Earth’s crust in soil, rocks, and minerals. The levels of arsenic found in drinking water systems and private water supplies across the United States vary widely.

Arsenic occurs naturally in the environment and as a by-product of some agricultural and industrial activities. It can enter drinking water through the ground or as run-off into surface water sources.

Some people who drink water containing arsenic in excess of the U.S. Environmental Protection Agency’s (EPA) standard over many years could experience skin damage or problems with their circulatory system and may have an increased risk of developing cancer. Read more about Arsenic in Drinking water on the EPA Website.

Disinfection By-products: Community water may contain viruses and bacteria that can cause illness, such as gastrointestinal disorders or diarrhea. Community water suppliers disinfect their water to kill these viruses and bacteria. Chlorine is the most commonly used disinfectant, sometimes used in combination with other disinfectants, such as ozone, chloramine, chlorine dioxide, and ultraviolet light.

Disinfection by-products (DBPs) are a family of chemicals formed when these disinfectants react with naturally occurring organic matter and other substances in the source water. The levels of disinfection by-products depend upon the nature of the source water, the type of treatment to remove particles and organic matter, and type and concentration of disinfection.

The risk of illness from disinfection by-products 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 result from long-term exposures.

Surface water sources such as reservoirs and streams are more likely to have higher disinfection by-product levels than disinfected groundwater sources. However, in some states (for example, Florida and Texas) where drinking water comes from groundwater with high levels of natural organic material, groundwater is also associated with high levels of DBPs. If you get your drinking water from a private drinking water well, disinfection by-products are unlikely to be present in the water.

EPA requires that water systems use treatment methods to reduce the formation of disinfection by-products and to protect people from waterborne disease and the potential harmful effects of DBPs. Read more about Disinfection by Products on the EPA Website.

Lead: Lead is a naturally occurring bluish-gray metal found in small amounts in the Earth’s crust. Lead can be found in all parts of our environment. Much of it comes from human activities, including burning fossil fuels, mining, and manufacturing.

Lead has many different uses. It is used in the production of batteries, ammunition, metal products (solder and pipes), and devices to shield X-rays. Because of health concerns, lead from paints and ceramic products, caulking, and pipe solder has been dramatically reduced in recent years. The use of lead as an additive to gasoline was banned in 1996 in the United States. It is also a minor constituent in brass plumbing fixtures.

You can be exposed to lead in several different ways:

Typically, lead enters drinking water after it leaves the local treatment plant or well. Therefore, the source of lead in a home's water is most likely from corrosion of pipes or solder in household plumbing.

Children can be exposed to lead in the household by eating lead-based paint chips, inhaling house dust containing lead particles, or playing with toys that contain lead. Homes built before lead-based paint was banned in 1978 or such homes being renovated (for example, lead-based paint abatement) pose greater risks of lead exposure than newer homes.

Exposure can occur occupationally. Some health care products or folk remedies contain lead. Read more about Lead on the EPA website.

Nitrate: Nitrate and nitrite are nitrogen-oxygen molecules that can combine with various organic and inorganic compounds. Nitrate is the form commonly found in water, often in areas where nitrogen-based fertilizers are used. Vegetables, food, and meat are the major sources of nitrate exposure. The greatest use of nitrates is as a fertilizer. Read more about Nitrates on the EPA website.

Data and information for this site are still being developed and added.  We welcome your comments and feedback.

This effort is supported by funding from the U.S. Centers for Disease Control and Prevention Environmental Public Health Tracking Program, Cooperative Agreement Number 5U38EH000619-02. The contents of this Website are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention.