Radon in Water Q & A
Advisory Report - November 2003
Radon in Water Q & A
As Radon Testing providers for 18 years, we receive many questions about the effects of Radon in water. Below are the top twelve.
Q: Should everyone test their water for radon?
A: While radon gets into some homes through the water, it is important to first test the air in the home for radon. If a high level is found during the air test, and the home has a private well, it is recommended that you test the well water for radon.
Q: How do you test for radon in water?
A: Testing water for radon is straightforward and should be performed by a trained radon technician. First, a sample must be carefully drawn from the well. This is normally done by selecting a water faucet as close to the well head as possible. It is important that the water collected in the sample is from the well and not water that has been sitting in the plumbing. The sample is then shipped to a lab that specializes in radon in water analysis.
Q: How does radon get into the water in the first place?
A: Radon is decayed from radium which originates from Uranium. As time passes, radium deposits are exposed to fissures that have formed in the rocks through erosion. Drilling wells will often open up fissures in bedrock that would then be in contact with radium deposits. When water is in direct contact with a radium deposit, radon is directly infused into the water as the radium decays.
Q: Is there an EPA "Action Level" for radon in water?
A: No. There are no proposed standards for private household water supplies. However, EPA has proposed an action level for public drinking water supplies. This proposal is currently being evaluated. The proposed action level is 300 pCi/L (pico Curies per liter) with an alternate action level of 4000 pCi/L. The alternative action level would be allowed if the municipality actively promotes radon in air testing for their homes. There are certain states that have set guidelines for private household water supplies. These range from 2,000 pCi/L to 20,000 pCi/L depending on the state. This is expected to change once EPA and Congress set the action level as proposed.
Q: I tested my well water for radon and it was high. How can I fix it?
A: There are several methods available for removing radon gas from water. One of the better methods is an aeration system called Shallow Tray Aeration. This type of system can remove as much as 99.8% of the radon from the water. Another popular method is Granular Activated Carbon (GAC) filter tanks. GAC systems are less expensive to install and operate but require more maintenance and testing to keep them operating efficiently. Removal rates for GAC systems range from 75% to 99%.
Q: Are there any dangers associated with drinking water that contains radon?
A: The primary health risk associated with radon in water is lung cancer; which would occur from breathing the radon and radon decay products released from the water. There is a health risk for consuming water that contains radon. Based on a second 1999 NAS report on radon in drinking water, the EPA estimates that radon in drinking water causes about 168 cancer deaths per year, 89 percent from lung cancer caused by breathing in radon released from water, and 11 percent from stomach cancer caused by drinking radon-containing water.
Q: I have a Granular Activated Charcoal (GAC) system in my home for removing the radon in my water. Do I need to worry about maintenance?
A: Yes. GAC systems are prone to fouling by other contaminates which can reduce performance. The carbon bed needs to be replaced periodically. As a minimum, the system should be retested after installation and then after one month, 6 months, 1 year and then once each year thereafter until the carbon is replaced. The results of these tests, along with the calculation of lead 210 build up, will determine how often the carbon should be replaced.
Q: Are there any other problems I need to worry about with my GAC system?
A: Yes. GAC systems are a source of low level gamma radiation exposure due to accumulated radon decay products. The strength of the gamma source will diminish as the distance from the tank increases. If you can not maintain a safe distance from the tanks, you will need to consider some form of shielding. Water shielding with an encapsulated water vessel is considered to be an economical solution.
Q: How does the radon in the water get into the air in my home?
A: Radon escapes from water when its surface comes into contact with air. So if you increase the amount of water surface area exposed to the air, you will increase the amount of radon that escapes from it. Temperature is another factor in the amount of radon released from the water. Therefore, because showers, dishwashers and washing machines increase the water to air surface contact, and because these typically use hot water, they are the major contributors of radon release from water.
Q: Wow, my report says that I have 20,000 pCi/L of radon in my water! Should I evacuate my home?
A: The rule of thumb is that it takes about 10,000 pCi/L of radon in water to increase the average residential radon level by 1 pCi/L. Therefore, with 20,000 pCi/L of radon in your water, you should expect this to add about 2 pCi/L in the air of your home. (Remember that the EPA action level for Radon in the air is 4 pCi/L.)
Q: I get my water from a public water supply. Should I still test the water for radon?
A: Generally the answer is no. Water being supplied from a public source typically comes from reservoirs giving radon plenty of chance to escape from the water surface. However, some public water comes from shared wells. If you are concerned that the radon might be coming from the public water, you should contact your public water supplier.
Q: We did a radon in water test and found we have 30,000 pCi/L. Should I be worried about anything else besides the radon?
A: Yes, there is a possibility that you could also have elevated levels of radium and uranium in the water. It would be advisable to perform a gross alpha analysis for any reading higher than 20,000 pCi/L.
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Contributed by Martin Smith
Director of Training and Residential Operations
U.S. Inspect, LLC