tapwaterA new study published today (April 30) is showing that drinking tap water in the Golden State could increase your risk of a deadly disease.

Researchers from the Environmental Working Group, an environmental advocacy group, estimated that the contaminants found in public water systems in California could contribute to nearly 15,500 cancer cases over the course of a lifetime. Some 2,737 different public water systems across the state of California were assessed. The systems are the main providers of drinking water in the state, serving 98 percent of the state’s population. They are regulated by the federal Safe Drinking Water Act and overseen by state regulators.

Contaminant levels from 2011 to 2015 were examined. The authors divided the water systems into four different categories of risk. The highest category estimated an additional cancer risk of more than 1 in 1,000 people being diagnosed with cancer over the course of a lifetime from drinking tap water.

One of the concerns was arsenic contamination along with radioactive elements like uranium.

Water systems test for contaminants to maintain a safe drinking water supply.