Answer to Question #1426 Submitted to "Ask the Experts"

Q

I am purchasing a home and had a radon test conducted. The basement level reading was 9.8 pCi L^-1 (exceeding the EPA level of 4.0). Assuming these results are confirmed, the house will require a subterranean remediation system (using a fan system and PVC piping). My understanding of radon is that the alpha particles decay into gamma and other particles and that the gamma particles will penetrate the PVC, whereas in the alpha state they would not. A few questions:

• What are the risk factors of the gamma radiation coursing through the mitigation system 24 hours per day? What level of gamma radiation would be expected in this situation? What is that level comparable to (for example, a TV on 24 hours per day)?
   
• Is the risk of living in a house that requires a mitigation system to bring radon to a safe level higher than living in a house that is "naturally" at a safe level?

A

Let me begin with some general comments that might not be necessary: First: The Environmental Protection Agency (EPA) makes the following recommendations regarding the measurement: "The test kit should be placed in the lowest lived-in level of the home (for example, the basement if it is frequently used, otherwise the first floor). It should be put in a room that is used regularly (like a living room, playroom, den, or bedroom)." If the basement will not be regularly occupied, it might not be an appropriate location for a measurement. The concentrations on upper floors would normally be expected to be lower than that in the basement. Second: A decision to remediate should not be made on the basis of a single short-term screening measurement because their 4 pCi L^-1 guideline is an annual average value. The EPA notes that after an initial short-term screening measurement, you should "follow up with either a long-term test or a second short-term test:

• For a better understanding of your year-round average radon level, take a long-term test.
• If you need results quickly, take a second short-term test."

Presumably, this is the confirmation you are referring to. Having said that, radon is a radioactive gas that decays into radioactive "decay products" (sometimes called daughters) that for the most part will attach to dust particles in the air. The "risk" associated with radon is the possibility that lung cancer might result due to the radiation energy deposited in the lungs as a result of the inhalation of the decay products. These decay products emit several types of radiation: alpha, beta, and gamma. The assumed risk is almost exclusively associated with the alpha particles depositing their energy in the lung tissue. The gamma ray emissions are not a concern. The actual gamma ray emissions from the radon traveling through the mitigation system would be so low as to be immeasurable. It might be possible to calculate a theoretical "risk" associated with these gamma emissions but such a risk would be extraordinarily small—so small that it would have no meaning that could be understood in a real way. The active mitigation system you describe will require electricity to run and it might increase your heating and air conditioning expenses somewhat. Also, this system will have to be inspected and the fan might have to be replaced every few years (for example, five years). Although a passive mitigation system would not be as effective as one that uses a fan, it is possible that it might be good enough to lower the radon concentrations below 4 pCi L and save you these types of expenses. Aside from the fact that an active mitigation system is subject to failure, a home that has reduced radon by mitigation is no less safe than a home that is at "at a naturally safe level" as you describe it. Because the mitigation system might reduce the radon concentration well below the 4 pCi L^-1 guideline, your radiation exposure could be lower than if you moved into a home that didn't require mitigation. The EPA has produced numerous publications about radon and radon mitigation. Two that might be of interest are "A Citizen's Guide to Radon" and "Consumer's Guide to Radon Reduction How to Reduce Radon Levels in Your Home." Paul Frame, CHP, PhD