Exposure to radon gas in the indoor air of your home is a health risk. It is more likely that radon gas will enter a building through contact with the soil, but it is possible for it to come through the water too. The risk of radon in the water supply is that the radon gas is released into the air and inhaled when showering or using a faucet. The greatest health danger is lung cancer from prolonged inhalation of radon gas in the air. So far, research has shown that there is very little risk of stomach cancer from swallowing water with radon in it.
First, it’s most important to test for radon gas in the air. Whether the test results from the lab show elevated levels of radon in the air or not, have your water tested for radon gas, especially if you have a private well or spring. Radon in the water is more of a problem when its source is ground water such as a private well or a public water supply system that uses ground water. Radon is usually not a problem if the home’s water source comes from surface water. Contact your local water supplier if you are concerned about radon in the water to find out if the public water is tested and/or treated before being delivered to your home. Many public water systems do address radon levels in the water.
If you do have a private water source, it is recommended to test your water for radon gas. A Radon Gas in Water Test Kit (rn-h2o) is easy to use. A sample of water from your faucet is collected in a small glass collection vial and sent to our lab for an analysis. It is very important to ship the water sample to the lab immediately, it must be received within eight days of ending the test. Lab reports are available the next business day after being received.
What levels of radon in water should I be concerned about?
There is currently no federally-enforced drinking water standard for radon. EPA has proposed to regulate radon in drinking water from community water suppliers (water systems that serve 25 or more year-round residents). EPA does not regulate private wells.
EPA has proposed to require community water suppliers to provide water with radon levels no higher than 4,000 pCi/L, which contributes about 0.4 pCi/L of radon to the air in your home. This requirement assumes that the State is also taking action to reduce radon levels in indoor air by developing EPA-approved, enhanced State radon in indoor air programs (called Multimedia Mitigation Programs). This is because most of the radon you breathe comes from soil under the house. This option gives States the flexibility to focus on the greatest problems, by encouraging the public to fix radon in indoor air problems and build homes that keep radon from entering.
Under the proposed regulation, States that choose not to develop enhanced indoor air programs, community water systems in that State will be required to reduce radon levels in drinking water to 300 pCi/L. This amount of radon in water contributes about 0.03 pCi/L of radon to the air in your home. Even if a State does not develop an enhanced indoor air program, water systems may choose to develop their own local indoor radon program and meet a radon standard for drinking water of 4,000 pCi/L.
What is the Radon Transfer Ratio? As radon escapes from water it raises the radon level of the air within a building. The “radon transfer ratio” predicts the increased radon level of indoor air in a home due to the off-gassing of radon from the water. The transfer ratio can vary widely from one home to another. On average, this transfer ratio predicts that 10,000 pCi/L (picocuries per liter of air) of radon in water can be expected to increase the overall annual average radon concentration of the air in a conventional single family home by approximately 1 pCi/L. To illustrate this conversion assume the following example: if the radon in water concentration was 5,000 pCi/L, and the radon in the air measure was 3 pCi/L, then 0.5 pCi/L of the airborne radon would likely be attributed to the water and the remaining 2.5 pCi/L would be attributed to radon gas migration up from the soil through the home’s foundation. It is important to note that this ratio is an approximation and may vary widely from home to home.
There are two ways to fix the problem of radon in the water. One way is a point-of-use treatment, which removes radon from your water at the tap. This will only treat a small portion of the water that you are directly using and doesn’t prevent the inhalation risk of radon gas mixing with the air. The other way to fix the radon problem is to treat it at the point-of-entry and remove radon from the water before it enters your home. Point-of-entry treatment uses either an aeration device or granular activated carbon (GAC) filters. GAC filters usually cost less than aeration devices, but the filters can collect radioactivity and may require special disposal methods. Most radon mitigation specialists prefer an aeration system as the most effective method to remove 95-99% of radon from the water. The aeration device combines spray and diffused bubble aeration to remove the radon gas from the water and sends aerated vapors to the outside of the home through an exhaust system. The treated water then is safely sent to the water tap and poses very little risk of radon gas inhalation if installed correctly. Consult with a radon mitigation specialist to determine the best treatment method and professional installation.