Answer to Question #8526 Submitted to "Ask the Experts"

Category: Environmental and Background Radiation — Granite and Stone Countertops

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

Q

Could you recommend a portable device for measuring radiation of granite and stones? My home was just built and I'd like to test how safe the environment is I'm going to live in, including granites and blocks in kitchen and walls.

Manufacturer and model name sharing is highly appreciated.
 

A

In most instances, you do not have to be concerned about the potential for harm from the radiations emitted from products used in the home. You can review various questions and answers, related to radiation exposure from and measurements of stone products used in the home, on the Health Physics Society (HPS) Ask the Experts website. Type "granite" in the search box, click "Find," and see, for example, questions 7746, 7834, 3991, 7855, and 7922.

If you still feel that you want to make some independent measurements, here are a few suggestions and things to keep in mind. The radiation of most concern from an exposure point of view is gamma radiation. The detector you use should be able to measure the exposure rate or dose rate from the gamma radiation.

There are a number of portable instruments that would be suitable for such measurements. Many people have used Geiger-Mueller (GM) detectors that have a thin window. The GM detectors are among the most economical detectors available, but you must exercise caution in interpreting the readings (see the discussion in the answer to question 7746). Also, the net reading that is typical when a gamma measurement is made in contact with a granite slab is comparable to the normal gamma background dose rate, and many GM detectors have marginal sensitivity for making such measurements, with acceptable precision.

A better detector for measuring the gamma dose rate is a tissue-equivalent scintillation detector such as that sold by Thermo Scientific. If you are unwilling or unable to come up with the cost of such an instrument, you can find comparable instruments for rent from some companies. See, for example, advertisements from Environmental Equipment and Supply and Environmental Restoration Group.

People have also had concerns about the potential for radon, a radioactive gas, being generated by decay of radium in stone products. Analyses done to date have not supported a need for significant concern regarding radon generation from typical granite countertops. In addition to several of the questions and answers cited above, also see the informational online paper from the HPS regarding this issue for more details about radon from natural materials. Typically, the radon that enters the home from the earth produces much greater radon airborne levels than those produced from granite and other earthen products in the home. You state that your home was recently built. As such, it is quite likely to be energy efficient, with low air leakage. Such designs are desirable from an energy-usage standpoint, but they can also lead to the buildup of radon in the home air. I would definitely recommend that you have the home tested for radon levels. I believe, independent of your concern with the potential for exposure to radiations from natural products in the home, the potential for significant radon concentrations from emanation from the ground warrants measurements. I believe every homeowner should have such an evaluation performed if it has already not been done.

I wish you much happiness in your new home and expect that the radiation levels associated with any natural products used in your home will not be a health concern.

George Chabot, PhD, CHP

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 14 September 2009. 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.