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Radon in private well water

Radon is a substantial health risk in many Wisconsin homes. There is a risk of developing cancer from long term exposure to radon in air and water. If you get your drinking water from a private well, this page will guide you in evaluating whether radon is a concern.

Radon is

  • A naturally occurring radioactive gas
  • Colorless, odorless and tasteless
  • Found in both air and water
  • Found with uranium in small amounts in most rock, soil and groundwater
  • Created when uranium decays to radium which then decays to radon
  • Measured in water and air in units of picocuries per liter (pCi/L)

Cancer risks from radon

  • The U.S. Environmental Protection Agency (EPA) estimates that a person has a 1% (one in 100) risk of developing cancer from life-long household use and consumption of water containing 20,000 pCi/L of dissolved radon, or breathing air containing 4 pCi/L of radon. This is considered a high risk when compared to the cancer risks from other contaminants in drinking water, which are in the range of one in 10,000 to one in 1 million.
  • The EPA recommended standard for radon in air is 4 pCi/L.
  • The office of the U.S. Surgeon General estimates that radon causes approximately 14,000 cancer deaths per year in the United States.
  • Breathing radon gas is second only to smoking as a cause of lung cancer.
  • If you smoke, and your home has high levels of radon gas, your risk of lung cancer is especially high.
  • An additional cancer risk comes from drinking water containing dissolved radon. Dissolved radon spreads throughout the body in the bloodstream potentially affecting the liver, stomach, intestines and lungs.

Radon enters dwellings in two ways

  • Radon gas, moving through the soil, enters buildings through cracks and holes in the foundation.
  • Radon gas easily escapes from well water containing dissolved radon once the water is exposed to air. This occurs at household taps, washing machines and showers. If there is radon in your well water it will increase your exposure to radon in air.

Where is water containing radon found?

  • Radon levels are always low in surface waters such as lakes, streams and rivers.
  • The highest concentrations of dissolved radon are found in groundwater flowing through granite or granitic sand and gravel formations commonly found in northcentral and northwestern Wisconsin.
  • Every well in Wisconsin has some level of dissolved radon in it. It is not possible to know if you have high radon levels in your drinking water without testing.

Test your household air for radon first

  • Your family's greatest risk comes from breathing radon gas.
  • Radon in air test kits are available at most hardware stores. Test kits should display the phrase "Meets EPA Requirements."
  • A list of EPA certified professionals that can test your household air for you is available from the Wisconsin Department of Health [exit DNR].

If radon in household air exceeds 4 pCi/L

Modify your water supply if necessary

  • You should consider modifying your water supply to reduce radon levels if the radon level in your well water is over 4,000 pCi/L.

Reduce exposure to radon

To reduce your exposure to radon from your water supply consider the following four options:

  1. Treat the water with aeration equipment. These systems are considered to be the most effective treatment systems in reducing radon levels. They typically cost about $3,500 and must be properly designed to prevent fouling by iron, iron bacteria or water hardness.
  2. Treat the water with granular activated carbon (GAC). These devices are effective yet often require a pretreatment system. GAC devices have filters, which may accumulate hazardous levels of radiation when treating water with radon levels of 4,000 pCi/L and higher. Spent filters may need to be handled and disposed of with care. Small carbon filters attached to kitchen faucets or placed under a sink are inadequate to treat your water for radon.
  3. Connect to a public water utility or a neighbor's well that has been tested for radon and the levels are low. Using bottled water for drinking will reduce your risk from radon ingestion but will not eliminate the problem of radon gas escaping from your well water into your household air.
  4. Constructing a replacement well should be considered only as a last resort. This is an expensive option and will not necessarily yield water with lower radon levels.

Each of the above options has advantages and disadvantages and requires professional advice. Contact DNR Bureau of Drinking Water & Groundwater for further information about these options before deciding a course of action.