Answer to Question #12855 Submitted to "Ask the Experts"

Category: Environmental and Background Radiation — Radon

The following question was answered by an expert in the appropriate field:

Q

I live in an area of New Jersey where there is substantial radioactivity in the groundwater. I had radon in air, radon in water, and gross alpha tests conducted before I moved into my house in 2015—all three areas needed addressing.

My most recent radon in water test yielded a result of 1,510 pCi L-1 (55.9 Bq L-1)*. I have two carbon tanks in my basement to mitigate the radon in my water. I also have a radon system installed for my air. My most recent gross alpha test (pre-treatment) was 7.1 pCi L-1 (0.26 Bq L-1) initial, 5.2 pCi L-1 (0.19 Bq L-1) final. As a result, I have a water softener installed in my basement (before the carbon tanks) as well as a reverse osmosis system installed in my kitchen.

My concerns are as follows: I feel like I'm living on top of a nuclear waste dump. I know that sounds dramatic, but how much of that radioactivity that my house is sitting on is reaching me and my family inside my home? Also, as far as the carbon tanks are concerned, I know they can become radioactive as a result of the radon that is accumulating inside of them. They do get read with a "geiger scanner" every year by the company that installed my system, but how much risk is my family at having two potentially "hot" carbon tanks sitting right below our living area? And what about my well tank? Is that also radioactive? Is there anything else I should be concerned about? I don't know much about radiation, just that it gives me anxiety, so any information you could provide me with would be so very appreciated. 

A

The data you presented on radon measurements in your water, 1,510 pCi L-1 (55.9 Bq L-1), indicates that radon is a very small or negligible risk to you or members of your family. Given the fact that the carbon tanks are located in the basement and not in an area of the home that is routinely occupied, the small amount of direct radiation that you would receive from the system should not be a problem. However, your concerns for radiation exposure are normal especially considering the information commonly presented by the media. Generally, stories about radiation are presented as something to be avoided. You have taken an important step to deal with your concerns by seeking help from a radon professional.

You noted that you feel like you are "living on top of a radioactive waste dump." What you may not realize is that no matter where you are, you are exposed to radiation from the ground and from outer space. There is no zero for radiation. We live in a radioactive world without any apparent effects. The information you presented on efforts to reduce radon exposures show that you are doing all the right things. Based on the test result for water at 1,510 pCi L-1 (55.9 Bq L-1), I would conclude that this source of radon is unlikely to ever result in any consequences. Ingestion of water containing radon is an extremely low risk, especially at the level you reported where the risk would be essentially zero. Removal of radon with charcoal can result in a small accumulation of gamma radiation over a long period of time. Even if gamma radiation does accumulate, the measurable exposure rate will decrease rapidly in a few feet and will be shielded by the floor and walls surrounding the charcoal tanks. Thus, you would have to live in close contact with your charcoal tanks to receive any significant radiation exposure due to the accumulated decay products of radon.

A University of North Carolina study on the use of activated carbon to remove radon from drinking water noted that radon and its short-lived decay products can produce a radiation field near the system but that the exposure can be minimized by installing the system in an area where it will not be a problem (Watson 1991). Your basement would seem to be such an area. The EPA, in its online information about radon in drinking water, also states that radioactivity collects on granular activated carbon filters. The National Academy of Sciences published a report on Radon in Drinking Water that includes a calculation of the gamma radiation dose from granular activated water treatment units probably similar to the one in your residence (NRC 1999). The estimated dose at a meter from the tank was about two times above the normal natural background dose in New Jersey. The dose would decrease rapidly with distance from the tanks and because of shielding provided by the residential structure itself. You noted that your carbon tank system vendor measures the radiation levels annually. This should give you a level of comfort that the issue of direct radiation exposure is being addressed. 

With regard to your "well tanks," you indicated that measured gross alpha concentrations in your water, pre-treatment, are well within the EPA gross alpha drinking water standard of 15 pCi L-1 (0.56 Bq L-1 ). I am not sure what you mean by "well tank." However, if this is the tank that stores your raw water pre-treatment, radiation levels in that area should not be a problem given the relatively low gross alpha concentrations indicating that the radium concentration is also relatively low.

Please don't hesitate to contact us if you have more questions or need more explanation. Your concerns are understandable but as long as you and members of your family are not in close or direct contact with the carbon tanks and they are handled properly, your radiation exposure should be consistent with natural background levels.

Ray Johnson, PhD, CHP
Jan Johnson, PhD, CHP

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

References

National Research Council. Risk assessment of radon in drinking water. Washington, DC: The National Academies Press. https://doi.org/10.17226/6287.

Watson JE, Crawford-Brown DJ. Use of activated carbon to remove radon from drinking water. UNC-WRRI-91-260. Department of Environmental Sciences and Engineering. University of North Carolina, Chapel Hill, North Carolina; 1991.

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 10 June 2019. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.