Answer to Question #10375 Submitted to "Ask the Experts"

We have a two-year-old child, a four-year-old child, and a five-months-pregnant mother in our household. I am the father who does all I can to protect my family.

I've had our house extensively tested for radon gas and our air levels are all reading less than the mitigation threshold of 4 pCi L^-1 (150 Bq m^-3)* except for one place in a storage closet in our concrete-pad garage that nobody frequents often.

However, I had our private well water tested and the test found 210 Bq L^-1 of ²²²Rn.

It was recommended that we mitigate at this level but it was also recommended that we have broad spectrum radionuclide testing done on our water as well.

The tests found that we have 57.9 µg L^-1 of uranium in our well water which is almost twice the Environmental Protection Agency (EPA) allowed level in public drinking water supplies.

Our gross alpha readings are 2.0 Bq L^-1 which are over three times the EPA allowable limits for public drinking water and 10 times the recommended mitigation threshold of 0.185 Bq L^-1.

Our gross beta readings are 0.522 Bq L^-1 and all I have found so far is the max exposure for beta radiation is 0.04 mSv y^-1 and I do not know how to convert that.

The tests also found lower concentrations of the following:

0.046 Bq L^{-1 134}Cs

0.098 Bq L^-1 228Ra

0.050 Bq L^{-1 226}Ra

I switched us all to bottled water for our drinking and cooking for the last three months.

I had been using this unfiltered water to irrigate my outdoor garden and plants for the last five years and this well has been actively irrigating this property and household since 1991.

Should we stay here or leave this house? So far we have not found a company that says they can mitigate this level of uranium for us without putting in $10,000 to $30,000 worth of equipment.

*The radon concentration units are given here in pCi L^-1 (called traditional units) because that is the unit used by EPA. However, the Health Physics Society has adopted the SI (International System) of units and these are given in parentheses.

First, let us assure you as a concerned father that there is no immediate hazard to your children. However, that does not mean that some remediation efforts are not indicated. First, regarding the radon in your water, most of the dose attributable to radon in water arises when the radon transfers to air inside the structure during use, adding to that present from infiltration from the soil. A report of the National Research Council (NRC 1999) concluded that although there is variability in the transfer coefficient for ²²²Rn in water to ²²²Rn in air, the value of 0.0001 represented a good estimate. Thus 210 Bq L^-1 of ²²²Rn in water leads to approximately 0.021 Bq L^-1 of air. The dose attributable to radon from consumption of the water is very small (NRC 1999). If your indoor radon concentrations remain below 0.148 Bq L^-1 in the inhabited rooms, you need not be concerned about the radon in water or its contribution to indoor radon. If your indoor radon levels were to exceed 0.148 BqL^-1, conventional remediation to reduce radon infiltration from soil gas would likely be more effective in total reduction than water treatment.

As you have noted, the radioactivity levels reported in your water are above the established maximum values put forth by the Environmental Protection Agency (EPA) for uranium and gross alpha radioactivity in drinking water and, thus alone, are sufficiently high to warrant discontinuation of the use of the water for drinking and other consumption as you have done by using bottled water for drinking and cooking. In addition, the reported level for the two radium isotopes is 80% of the EPA standard. However, the water should be safe to use for irrigation purposes and thus this activity need not be discontinued. 

There are a number of treatment technologies available that can be used to reduce the level of uranium, radium, and total alpha activity in drinking waters. Softening with lime, treatment with alumina, filtration, and coagulation (at high pH), anion exchange, and reverse osmosis have been found effective to various degrees and under various conditions, removing up to 99% of the radium and uranium in some instances. 

The EPA has available on its website documents specifically describing control procedures that you may find useful; one particularly relevant document was prepared by Dennis Clifford of the University of Houston, Fundamentals of Radium and Uranium Removal from Drinking Water Supplies and provides a summary of treatment methods. The question of which, if any, of the available methods would be feasible and practicable for your situation would need to be determined through additional evaluation of your water and specific situation by qualified professionals. You should be able to obtain no-cost assistance from your local or state public health department, which can, in addition to helping you to assess your specific situation, advise you on where additional help might be available as well as provide information regarding availability and feasibility of commercial products. Thus informed, you should be able to make the appropriate decision of which way to turn. 

Ron Kathren, CHP
Tom Gesell, PhD

References
National Research Council. Risk assessment of radon in drinking water. National Academies Press: Washington, DC; 1999. Available at: http://www.nap.edu/catalog.php?record_id=6287. Accessed 5 February 2021.

Clifford D. Fundamentals of radium and uranium removal from drinking water supplies. University of Houston. Available at: https://www.epa.gov/sites/production/files/2015-09/documents/rads_treatment_dennis_clifford.pdf.  Accessed 5 February 2021.