Radium in California Drinking Water — 331 ZIPs Tested

Radium Contamination in California

ZipCheckup analyzed drinking water data across 2,630 ZIP codes in California for radium contamination. 331 ZIP codes have reported radium detections, and 32 have EPA violations on record.

The violation rate for radium in California is 1.2% of all ZIP codes — roughly in line with the national average.

EPA Standard for Radium

The EPA maximum contaminant level (MCL) for radium is 5 pCi/L (combined Ra-226 + Ra-228), governed by the Radionuclides Rule. Water systems that exceed this limit must take corrective action and notify consumers.

Worst ZIP Codes for Radium in California

These ZIP codes reported the highest radium levels in California based on CCR reports and EPA data:

Lowest Radium Levels in California

These ZIP codes had the lowest reported radium detections in California:

Health Effects of Radium

Radium is a radioactive element that increases cancer risk, particularly bone cancer. It accumulates in bones because the body treats it like calcium. The EPA estimates that drinking water with 5 pCi/L of radium over a lifetime poses a 1 in 10,000 cancer risk.

How to Remove Radium From Drinking Water

The most effective treatment for radium removal is Reverse Osmosis or Ion Exchange. Look for filters certified under NSF 58 standards.

Check Your ZIP Code

Use the ZipCheckup water quality search to see radium data for your specific water system in California.