Radon occurs at a much higher level in water than air. It is measured in pico-curies of radiation per liter of volume, which is abbreviated as pCi/L. While the maximum acceptable level of radon in air is pegged at 4 pCi/L in the United States, the upper safe level in water is estimated to be somewhere between 3,000 and 40,000 pCi/L, although the EPA has not defined that number yet.

    The dramatic difference in acceptable levels of radon between water and air is due to several factors:

1. Ingested water containing radon is believed to be an extremely low health risk. The U.S. Congress authorized the National Academy of Sciences to do an evaluation of the risk of radon in drinking water in 1998 as part of the Safe Drinking Water Act (SDWA), and the study committee concluded that only about 20 of the 13,000 stomach cancer deaths each year are due to consuming water with a high radon level.
2. The larger health risk is radon in the air inhaled into your lungs. About 160,000 people—most of them smokers—die from lung cancer each year. Approximately 19,000 of those deaths are attributable to a combination of smoking and indoor radon, because radon greatly enhances the cancer-causing effect of smoking.
3. The radon dissolved in water escapes into the air when showering or washing dishes, especially if the sink faucet has an aerator spout. But the conversion factor to the more-deadly airborne radon is low. It is estimated a 10,000 pCi/L level of radon in water raises the radon of the indoor air by only 1 pCi/L.

   To complicate things further, the level of radon in water does not directly correlate to the level in air. According to the National Academy of Sciences study, data indicates that the Northern United States and some areas in the South have higher than average indoor air radon, while New England states and some parts of the Southwest have higher levels of radon in water. The Appalachian and Rocky Mountain states, along with some parts of the Great Plains, have higher than average radon in both water and indoor air.

    Although radon testing of indoor air has become a standard part of due diligence for homebuyers in a real estate transaction, water radon testing is not that common in Florida. Also, the equipment that home inspectors use to test radon levels in the air is not suitable for water testing. 

    If you want to check your well water for radon, we suggest using a test kit from Pro-Lab, of Fort Lauderdale, Florida. You can purchase one at any Home Depot. If not in stock at your local store, they will order one for you. It costs under $8, and you send your water sample to the lab, along with a $40 lab fee, and get the results back in about one week. Pro-Lab uses the “liquid scintillation” method for evaluating the water, which is a technique approved by the EPA for water radon testing.

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Here’s links to a collection of our other blog posts about WELLS:

• What is the blue dumbbell-shaped tank at the well equipment?

• What is the tank marked "potassium permanganate" in the water treatment system for? 

• Does an abandoned well need to be capped or removed?

• Does a homeowner need a permit to drill a water well on their property in Florida? 

• Is a high iron level in well water a health hazard?

• How often should a well be disinfected? 

• Should I test my well water for arsenic?

• What size generator do I need to run my submersible well pump?

• Why would a well need to have a chlorinator/dechlorinator system? 

• Why does my well pump turn on and off every time I use water?

• What is the required water testing for an FHA, VA, or USDA mortgage application? 

     Visit our WELLS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.