• What is radon?

• How do you test for radon?

• How does radon get into your house?

• What are the options for reducing radon in water?

• What levels of radon are dangerous?

• Which option is best?

• What are the health impacts?

• References& More Information

Radon is a naturally occurring radioactive gas that occurs in most rock, soil, and groundwater.  Radon is the decay product of radium, which is the decay product of uranium.  Radon can be found in both air and water.  In fact, “every well in Wisconsin has some level of dissolved radon in it.” ¹  The EPA and USGS have stated that Wisconsin’s potential for radon is in AIR is between 2-4 pCi/L for most of the state, and above 4 pCi/L for mainly the central and southwestern parts of the state.⁵  (map-select Wisconsin)

Radon gas enters a home in two ways—through the soil and water.  Radon gas contained in soil enters homes through cracks and holes in the house’s foundation.  Radon gas dissolved in well water  enters the home when the water is exposed to air.  In the home, water is exposed to air at faucets, washing machines, dish washers, and showers.  Since radon is colorless, odorless, and tasteless, the only way to know if it exists in your house or water is to test for it.^1,2

What levels of radon are dangerous? 

The Safe Drinking Water Act Amendment of 1996 requires that the EPA (Environmental Protection Agency) set safe drinking water standards to protect public health. For each chemical, two standards are set, the Maximum Contaminant Level Goal (MCLG) and the Maximum Contaminant Level (MCL).  The MCLG is the ideal level below which there is no known health risk. The MCL is set as close as feasible to the MCLG, taking into account the use of technology and the costs associated with treatment.  These standards only apply to community water supplies, not private water systems.

As far as radon is concerned, there are no federal regulations for radon in air or water, yet.   Since radon is a known carcinogen, the MCLG is expected to be zero.  The EPA recommends that radon in the air not exceed 4 pCi/L (picocuries per liter). 

A 1995 Wisconsin DNR publication stated that the radon in water MCL is 20,000 pCi/L, but recommended taking treatment actions at levels of 5,000 pCi/L.¹  However,  the EPA withdrew its 1991 proposed MCL for radon in water in August of 1997.  Now the proposed MCL for radon in water is 300 pCi/L or the Alternative MCL (AMCL) is 4000 pCi/L with an approved Multi-media Mitigation Program. 

The Multi-media Mitigation (MMM) Program is simply an action plan to help reduce the overall amount of radon in a community.  The EPA is allowing higher levels of radon in water in communities that take action to reduce the overall radon exposure by doing public education and mitigation programs that reduce the amount of radon in the air.  For some communities, it will be easier to reduce the total radon exposure by helping people seal up cracks in their foundations, or by helping them put in ventilation systems, than to treat the community's water supply.  The MMM must contain four aspects:

·         Public involvement in developing the MMM

·         Quantitative measures for reducing radon

·         Strategies to achieve the quantity goals

·         A plan for tracking and reporting results.

The Alternative MCL applies to community water systems serving 10,000 people or less, and gives states a little flexibility in reducing the amount of radon in the air and water.  The water MCL and AMCL only applies to community water systems that use groundwater or a mix of groundwater and surface water.²

From a life-long exposure or consumption of radon gas, the EPA estimates that a person has a 1% risk of developing cancer, especially lung cancer. ¹ Another way of saying this is 1 person in 100 may develop cancer.  This chance of developing lung cancer increases even more if the person smokes.  According to the U.S. Surgeon General office, about 14,000 people/year in the United States die from radon-related causes. ¹ “EPA estimates that radon in drinking water causes about 168 cancer deaths per year, 89 percent from lung cancer caused by breathing radon released from water, and 11 percent from stomach cancer caused by drinking radon-containing water. “² Radon from water only accounts for 1-2% of the radon found in a household; therefore, radon from the soil/air is more dangerous than radon in water.²

The first step is to test the air in your house.  You may  purchase a radon in air test kit locally from the Portage County Health Department for $8.00 (short term) and $20.00 (long term).  Otherwise, you may purchase a test kit from a hardware store or contact a certified professional. 

If the radon in the air exceeds the standard of 4 pCi/L, then test your water.  Also, you may want to test your water for radon if your well is drilled into granite (whether or not the radon in the air is above 4 pCi/L).  The Wisconsin State Laboratory of Hygiene or other certified water-testing laboratories can test for radon in water.  The test costs an average of $50 per sample.  If radon in the well water exceeds 4000 pCi/L, then you may want to reduce your exposure to radon in the water.^1,2

What are the options for reducing radon in water?  

Once again, radon is found naturally in the rock, soil, and water.  There is no known way of eliminating radon from these sources.  So you will have to reduce the radon in your water before it reaches the interior of your home.  There are five treatment options:

1.       Install a high performance aeration system to remove radon up to 99% ^1,2

2.       Treat the water with granular activated  carbon (GAC) system. ^1,2

3.       Connect to a public or private water source that does not have high radon levels.¹

4.       Install a new well.¹

5.       Choose to do nothing.

In Wisconsin, treatment devices must be approved by the Wisconsin Department of Commerce.

Which option is best?  

Options 1: install a high performance aeration system is the recommended treatment option because it does not accumulate hazardous waste like Option 2.  There are many aerators on the market that can remove up to 99% of the radon. Many aerators are installed on the surface.  This type of system usually uses chambers or tanks to hold the contaminated water and the treated water.  Atmospheric air is injected below the water's surface and thoroughly mixed by the rotating propeller at high velocities.   These air bubbles mix with the water and allow the radon to escape to the outside before the water enters your home. The escaping gas must be vented above the roof line.  ⁴  The size of the tank and the length the water would have to remain in the tank will vary depending on the size of the aerator, the amount of water used, and the concentration of radon in the water.  A Wisconsin family of four uses an average of 250 gallons of water a day. Costs vary for the system and annual electric costs between $40-$80. 

Option 2 uses a GAC filter system which uses a filter to retain the radon. This type of filter requires relatively large amounts of carbon and a long contact time to be efficient. This filter will have to be replaced on a regular basis, and properly disposed of since the build up of radioactive materials may make it hazardous.⁴  The schedule for replacement would depend on the amount of water being used and the concentration of radon in the water. For many people, changing a filter makes this alternative less convenient, and could possibly still lead to contaminated water and other health risks.  For these reasons, option 1 is the preferred method of treatment.

References and More Information

1.       Wisconsin Department of Natural Resources, Bureau of Water Supply.  (1995).  Radon in Private Well Water. [PUBL WS-036-95].  Madison, WI: Wisconsin Department of Natural Resources.

2.       http://www.epa.gov/safewater/radon.html : EPA information on radon

3.       http://www.aireo2.com/aire-o2.htm: information on aeration systems

4.       http://www.hometest.com/facts/radon_facts.htm: information radon   

5.      http://www.hometest.com/facts/radon_levels.htm: map of radon levels on Wisconsin

6.       http://www.awqinc.com/article_radon_system.html: How to buy a radon aeration system

7.       http://www.radonandwater.com/newradon/h_water_aeration.html: waterborne radon reduction systems

8.       http://www.bae.ncsu.edu/programs/extension/publicat/wqwm/he396.html:information on radon 

9.    http://www.wqa.org/pdf/consumer%20briefs/contaminants.pdf: a chart of what removes what

10.  http://commerce.state.wi.uw/SB/SB-PlumbingProductsBrochure.pdf: Department of Commerce rules on treatment devices

11.  http://www1.uwex.edu/ces/pubs/pdf/G3558_5.pdf: Choosing a Water Treatment Device

12.  http://www.wqa.org: Water Quality Association, a trade association for the water treatment industry