Drinking Water

What is drinking water contamination?

Most drinking water in California meets health and safety standards, but the water we drink sometimes becomes contaminated with chemicals or bacteria. Both natural and human sources can contaminate drinking water. Natural sources can be found in rocks and soil or come from fires. Human sources include factories, sewage, and runoff from farms.

Why is this indicator included in CalEnviroScreen?

Nitrate from fertilizer or animal waste can leach into groundwater and contaminate wells. Nitrate can cause blue baby syndrome (methemoglobinemia) and may cause birth defects and miscarriages.
Arsenic occurs naturally in some rocks and soil and is often found in groundwater in California. Arsenic is known to cause cancer.
Poor communities and people in rural areas are exposed to contaminants in their drinking water more often than people in other parts of the state.

How do we measure drinking water contaminants in CalEnviroScreen?

The indicator combines information about 10 contaminants and 2 types of water quality violations that are sometimes found when drinking water samples are tested.
We calculated average concentrations for the contaminants in each water system.
A complete description of the Drinking Water Contaminants indicator can be found in the CalEnviroScreen 2.0 report.

More information on the drinking water indicator

Methodology for a Statewide Drinking Water Contaminant Indicator
Microsoft Excel Spreadsheet: Average concentrations and percentile scores for each contaminant used to calculate the overall drinking water indicator by census tract.
ArcGIS Geodatabase: Locations of all community water systems used in the drinking water indicator represented as points. Additional information describing the data and its limitations is part of the geodatabase (metadata). Zipped file can be unzipped, then opened using ArcGIS software (ArcGIS is a paid subscription).

Shapefile: Locations of all community water systems used in the drinking water indicator represented as points. Additional information describing the data and its limitations is part of the geodatabase (metadata). Zipped file can be unzipped, then opened using ArcGIS software (ArcGIS is a paid subscription).