Radon in Water
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How does radon get in water?
When the ground produces radon, it can dissolve and accumulate in underground water sources (called ground water). When water containing radon is run for showering, washing dishes, cooking, and other uses, radon gas escapes into the air. Some radon also stays in the water. Radon can be a concern if your drinking water comes from a well that draws from an underground source, though not all water from underground sources contains radon. If you get your water from a public water system that serves 25 or more year-around residents, you will receive an annual water quality report. These water quality reports include information on what is in your water, including radon if it has been tested. Radon from lakes, rivers, and reservoirs (called surface water) is of much less concern. Most of the radon in surface water is released from the water before it enters the distribution system.
Does radon in drinking water pose a risk?
In most cases, radon entering the home through water will be a small source of risk compared with radon entering from the soil. The EPA estimates that indoor radon levels will increase by about 1 pCi/L for every 10,000 pCi/L of radon in water. Only about 1 percent to 2 percent of indoor radon in the air comes from drinking water. Based on a National Academy of Science report
, the EPA estimates that radon in drinking water causes about 168 cancer deaths per year: 89 percent from lung cancer caused by breathing indoor air that contained radon released from water, and 11 percent from stomach cancer caused by consuming water containing radon. While radon in water is not a problem in homes served by most public water supplies, problems have been found in well water. If you've tested the air in your home and found a radon problem, and your water comes from a well, contact a lab certified to measure radiation in water to have your water tested. Call the EPA's Safe Drinking Water Hotline, (800) 426-4791, to get information on locating a certified lab. If you're on a public water supply and are concerned that radon may be entering your home through the water, call your public water supplier.
Should drinking water be tested?
Because radon in indoor air is the larger health concern, the EPA recommends that you first test the air in your home for radon before testing for radon in your drinking water. The EPA and the Surgeon General recommend testing all homes for radon in indoor air (and apartments located below the third floor). The EPA recommends that you take action to reduce your home's indoor radon levels if your radon test result is 4 pCi/L or higher. If you have tested the air in your home and found a radon problem, you may also want to find out whether your water is a concern. If you get water from a public water system, find out whether it comes from a surface (river, lake, or reservoir) or underground source. If the water comes from a surface-water source, most radon in the water will be released into the air before it reaches your tap. If the water comes from a ground-water source, call your water system and ask if they've tested the water for radon. If so, ask for their Consumer Confidence Report. If you have a private well, the EPA recommends testing your water for radon. The Safe Drinking Water Hotline, (800) 426-4791, can provide phone numbers for your state laboratory certification office. You can also call the National Radon Program Services Hotline, (800) SOS-RADON, for your state radon office's phone number. Your state laboratory certification office or state radon office can direct you to laboratories that are able to test your drinking water for radon.
What do the results of a water test mean?
Estimate how much the radon in your water is elevating your indoor radon level by subtracting 1 pCi/L from your indoor air radon level for every 10,000 pCi/L of radon that was found in your water. (For example: if you have 30,000 pCi/L of radon in your water, then 3 pCi/L of your indoor measurement may have come from radon in water.) If most of the radon is not coming from your water, fix your house first and then retest your indoor air to make sure that the source of elevated radon was not your private well. If a large contribution of the radon in your house is from your water, you may want to consider installing a special water treatment system to remove radon. The EPA recommends installing a water treatment system only when there is a proven radon problem in your water supply.
What levels of radon in water should I be concerned about?
Currently, there is no federally-enforced drinking water standard for radon. The EPA does not regulate private wells, but it is proposing to regulate radon in drinking water from community water suppliers (water systems that serve 25 or more year-round residents). The EPA proposed the rule in October 1999 and plans to finalize it in August 2000. The EPA is proposing two options. The first option would require community water suppliers to provide water with radon levels no higher than 4,000 pCi/L. Because about 1/10,000th of radon in water transfers to air, this would contribute about 0.4 pCi/L of radon to the air in a home. This level will be permitted if the state also takes action to reduce radon levels in indoor air by developing the EPA-approved, enhanced state radon in indoor air programs (called Multimedia Mitigation Programs). This is important 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, encouraging the public to fix their homes to reduce radon in indoor air and to build homes that keep radon from entering. A second option is provided for states that choose not to develop enhanced indoor air programs. Community water systems in those states 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. This will require them to meet a radon standard for drinking water of 4,000 pCi/L. This option enables overall risks from exposure to radon, both through air and water, to be reduced.
How is radon removed from water?
Radon can be removed from water by using one of two methods: aeration treatment, or granular activated carbon (GAC) treatment. Aeration treatments involve moving bubbling air through the water, which helps to strip radon from the water. An exhaust fan is used to vent the radon outdoors. GAC treatment filters water through carbon. Radon attaches to the carbon ,leaving the water free of radon. GAC filters tend to cost less than aeration devices. However, radioactivity collects on the filter, which may cause a handling hazard and require special disposal methods for the filter. For more information on aerators and GAC filters, contact NSF International, at (800) 673-8010, and the Water Quality Association, at (630) 505-0160. These are both independent, nonprofit organizations. In either treatment, it is important to treat the water where it enters your home (using a point-of-entry device) so that all the water will be treated. Point-of-use devices, such as those installed on a tap or under the sink, will only treat a small portion of your water and are not effective in reducing radon. It is important to maintain home water treatment units because failure to do so can lead to other water contamination problems. Some homeowners opt for a service contract from the installer to provide carbon replacement and general system maintenance.
*Source: National Radon Program Services