Water Quality
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What are Drinking Water Contaminants?

The water we drink may contain natural or man-made contaminants. Common sources of contaminants include eroding natural deposits in soil, rocks, and minerals, runoff from fertilizers, pesticides, and herbicides, and damaged or corroding pipes. Some drinking water contaminants may be harmful if consumed above certain levels or over a long period of time, while others are harmless.

Public water systems treat and monitor their water before the water is distributed to households, schools, businesses, and other properties. If a water system does not meet the required standards for treatment techniques or for safe levels of contaminants, a water system is required to notify their consumers and will receive a violation from the state. Heightened levels of contaminants in drinking water may occur for various reasons: a failure in the treatment process; a problem in the distribution system such as corroding or leaking pipes; or other external factors such as a leaking septic or sewage system, construction accident, or natural disaster.

While most people in California get their water from a community water system, some people rely on private wells or other unregulated drinking water supplies and are responsible for testing their own drinking water. When a private water supply is not regularly tested, consumers may be unaware if they are being exposed to a drinking water contaminant.

Health impacts associated with drinking contaminated water may include gastrointestinal illness, reproductive problems, cancer, and developmental and neurological disorders. The type and severity of health problem depend on a variety of factors such as the type of contaminant, how the contaminant enters the body, the amount of the contaminant that enters the body, and how often or for how long the exposure occurs.

Tracking California provides information on types of drinking water contaminants, health impacts of drinking contaminated water, avoiding drinking water contaminants, vulnerable populations, and drinking water monitoring and regulation. To track the presence of drinking water contaminants in California, we display the levels of certain water contaminants in water systems across the state in our Water Quality Viewer. We acquire this data from the State Water Resources Control Board. 

We also provide geographic data of community water system customer service areas in California in our Water Boundary Tool.