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By Bill Walker, Editor in Chief, and Wicitra Mahotama, Environmental Analyst

UPDATE: On Feb. 4, the White House withdrew Kathleen Hartnett White’s nomination to head the Council on Environmental Quality. A new nominee has not been named.

Drinking water for more than 170 million Americans contains radioactive elements at levels that may increase the risk of cancer, according to an EWG analysis of 2010 to 2015 test results from public water systems nationwide.  


Radioactive elements enter groundwater from natural deposits in the earth’s crust, and the levels can be higher when uranium mining or oil and gas drilling unearth these elements from the rock and soil. They produce radiation called “ionizing” because it can release electrons from atoms and molecules, and turn them into ions.

The EPA has classified all ionizing radiation as carcinogenic. There is clear evidence that high doses of radiation cause cancer in various organs. The probability of developing cancer decreases with lower doses of radiation, but it does not go away.

The developing fetus is especially sensitive to ionizing radiation. At doses higher than are typically found in drinking water, radiation has been shown to impair fetal growth, cause birth defects and damage brain development. But there is no evidence of a dose threshold below which a fetus would be safe from these effects.

Six radioactive contaminants were included in EWG’s Tap Water Database, including radium, radon and uranium. By far the most widespread are two isotopes of radium known as radium-226 and radium-228, which contaminate tap water in every state. The EPA does not have a separate legal limit for each isotope, only for the combined level of the two.

From 2010 to 2015, 158 public water systems serving 276,000 Americans in 27 states reported radium in amounts that exceeded the federal legal limit for combined radium-226 and radium-228.

But federal drinking water standards are based on the cost and feasibility of removing contaminants, not scientific determinations of what is necessary to fully protect human health. And like many EPA tap water standards, the radium limits are based on decades-old research rather than the latest science.

The EPA’s tap water limits on the combined level of the radium isotopes and the combined level of alpha and beta particles were set in 1976. They were retained in 2000, when the uranium standard was established.

To more accurately assess the current threat of radiation in U.S. tap water, we compared levels of the contaminants detected by local utilities not to the EPA’s 41-year-old legal limits, but to the public health goals set in 2006 by the respected and influential California Office of Environmental Hazard Assessment.

California public health goals are not legally enforceable limits, but guidelines for levels of contaminants that pose only a minimal risk – usually defined as no more than one expected case of cancer in every million people who drink the water for a lifetime.

California has separate public health goals for radium-226 and radium-228 that are hundreds of times more stringent than the EPA limit for the two isotopes combined. The EPA standard for radium-226 plus radium-228 is 5 picocuries per liter of water. The California public health goal for radium-226 is 0.05 picocuries per liter, and for radium-228 it is just 0.019 picocuries per liter. The lifetime increased cancer risk at the EPA’s level is 70 cases per 1 million people.

California has the most residents affected by radiation in drinking water. Almost 800 systems serving more than 25 million people – about 64 percent of the state’s population – reported detectable levels of radium-226 and radium-228 combined.

Texas has the most widespread contamination. More than 3,500 utilities serving more than 22 million people – about 80 percent of the state’s population – reported detectable levels of radium-226 and radium-228 combined.


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