A new study finds that normal water in California could boost the threat of cancer.

Researchers through the environmental advocacy group Environmental Working Group estimated that the contaminants present in public water systems in California could contribute to about 15,500 cancer cases there over the course of a lifetime. These cancer causing pollutants include chemical substances such as for instance arsenic, hexavalent chromium and radioactive elements such as uranium and radium. The analysis based on cancer cases was published Tuesday in the journal Environmental Health.

The highest category estimated of individuals with cancer was more than 1 in 1,000 people. The people were identified as having cancer from drinking tap water. Researchers failed to identify which water systems were considered high risk.

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