In some parts of the country, radon may be found in drinking water that comes from private wells, but is usually not found in surface public water sources like rivers, lakes, streams and reservoirs. Radon is a naturally occurring radioactive breakdown product of uranium that can dissolve and accumulate in ground water. However, the primary source of human exposure to radon is breathing radon that is found in the indoor air. Radon escapes from household water when it is agitated (ex. shower, dishwasher or faucet aerator) or left exposed to the air for long periods. It is estimated that every 10,000 pCi/L of radon found in the water will raise the radon levels in the air by and average of 1 pCi/L. This radon would be in addition to what may coming into the home from the rock and soil beneath the foundation. The risk associated with drinking radon in water (ex. stomach cancer) is very low.
NRSB and NRPP currently do not yet have certification programs for radon professionals to test or mitigate radon but both organizations will eventually establish these programs in a few years. ANSI/AARST recently published the first guidance standard for testing radon in well water and it may be found here: new radon in water testing standard This document established a recommended action level of 4,000 pCi/L for radon in ground water. ANSI/AARST is currently working on producing a new radon in water mitigation standard.
Of 1,500 known radon in water test results in Virginia, about 13% exceeded 4,000 pCi/L, but only about 4% exceeded 10,000 pCi/L.
MITGATION OF RADON IN GROUND WATER
If the radon test result is 4,000 pCi/L or higher but less than 10,000 pCi/L, then an activated charcoal filtration system may be used. These systems generally cost less than $3,000 and will also reduce many other water impurities as well. If using such a system to reduce radon, the carbon container should be located well away from habitable areas because the trapped radon atoms will continue to undergo radioactive decay and will emit gamma radiation. The carbon bed should also be changed on an annual basis, which may be a significant cost.
For radon levels greater than 10,000 pCi/L, an aeration system should be used. These systems can be installed in either a holding tank located in the home or some new systems may be installed directly in the well itself. These systems may cost $3,000 – 6,000 and will require periodic maintenance and cleaning. They can effectively reduce even extremely high radon levels.
See EPA’s web site for additional information on radon in drinking water.
Office of Radiological Health | 109 Governor Street, 7th Floor | Richmond, VA 23219
Telephone (804) 864-8150 | Fax: (804) 864-8155