What You Should Know About Radon in Water

test water for radon

test water for radon

The U.S. Environmental Protection Agency (EPA) says, “Test evey well for radon.”  However, there is currently no national recommended safe radon level for radon in water. The 1996 Safe Drinking Water Act Amendments required EPA to establish several new, health-based drinking water regulations, including a multimedia approach to address the public health risks from radon. Although proposals were made, none have been enforced.

The following is summarized and edited from a Position Statement dated March 16, 2016, regarding radon in water supplies compiled by the Technical and Science Committee of the American Association of Radon Scientists and Technologists (AARST)

Radon Exposure Risk

The most significant health threat posed by indoor radon gas is an increased risk of lung cancer from breathing the gas and its radioactive byproducts. The lung cancer risk varies based on the amount of radon in the air and the duration of exposure. While the risk increases the longer the polluted air is breathed in, any exposure can be dangerous. The U.S. Surgeon General, U.S. EPA, AARST, and the American Lung Association recommend that all homes be tested for radon, so that proper measures can be taken if radon levels are high. High levels of radon in groundwater can carry health risks as well; unfortunately, the EPA does not currently have sufficient data to identify specific areas of the U.S. most likely to have this issue.

Sources of Radon in Air and Water

The main sources of indoor radon gas are the soil and rock beneath buildings. There is always some amount of radioactivity occurring in soil, producing radon gas that can enter structures.

A less common but significant source of radon is groundwater in homes that have wells. Radon is easily released from water into the air while being used for purposes such as bathing, washing, and drinking. The radon risk from this source varies greatly depending on concentration of radon in the water, amount of water used, and building ventilation rate. Surface water does not carry this same risk, as there are usually very low levels of radon present.

Testing Methods for Radon in Water

The two methods currently recommended by the EPA for measuring radon levels in water are liquid scintillation counting and alpha scintillation cells. These are good indicators, but aren’t able to measure how much radon escapes from the water into the air. Use of these measurements to estimate exposure can result in large discrepancies due to differences in:  the amount of groundwater used by each home, the ventilation rates between homes, and the amount of radon that escapes from the water into the air.

Better estimates of radon exposure can be found through radon in air testing.  According to testing protocols, testing should be performed in the lowest (lived in) level of the building, with the test placed 20” above the floor and 12” from the walls. Another measurement should be taken in a location where there is substantial water use, as well as in another room on the same floor. To confirm that the water is causing a difference, a third measurement can be taken in another room on the same floor. If measurements are above the EPA recommended action level, the building should be retested. If high levels are present,  particularly on upper floors, the water should be tested. If concentrations of radon in the water are above 4000 pCi/L, the radon should be remediated to prevent elevated air levels.

Reducing Radon in Air and Water

The most effective system to reduce indoor radon levels in air is an active soil depressurization (ASD) system. For radon in water, the EPA has designated water aeration as the “best available technology.”

Who Should Test for Radon in Water?

It is recommended that water be tested by a qualified professional. Then, if results are high, contact a trained, experienced radon professional.  To find a qualified radon professional in your area, go to our Find a Radon Professional page.


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