Answer to Question #12718 Submitted to "Ask the Experts"

Is it safe to store food, pharmaceuticals, or other items on travertine, granite, or marble countertops? Is any radiation transmitted through or retained in the items? Also, is it safe to regularly make bodily contact with such countertops or bathroom vanities, such as leaning into them?

I will say up front that, based on information that has been accumulated regarding use of and exposure to the materials of interest, there is no good reason for you to be concerned about possible negative health effects from the material you describe and the activities that you might likely be involved in that are associated with contacting these materials.

Over the past several years, this Ask the Experts (ATE) website has had quite a few questions related to radioactivity in and radiation from granite used in kitchen countertops as well as other construction materials, such as some floor tiles, that incorporate materials extracted from the earth. There are small amounts of naturally occurring materials in such products and they do produce low-level, but measurable, radiation that is emitted from the material as well as small amounts of radioactivity, most notably radioactive radon gas that gets released from the uranium-containing granite or other material and mixes with the home air. Both marble and travertine typically have much lower concentrations of naturally occurring radioactivity than does granite. If you are interested, you can review some of the ATE questions and answers related to radioactivity in home building products at this link.  

Regarding the placement of food, drugs, and other materials on the countertop, there is no problem associated with the radiation entering these materials from the countertop. Some of the penetrating gamma radiation will enter the materials, but it will have no significant negative effects on the food or drugs. The radiation does not make the food or drugs radioactive and will not alter them in any measurable way. The only exception I would make would be in regard to placing raw, wet foods directly on the countertop for extended periods. Depending on the food type (e.g., its acidity content), the countertop could be stained. Additionally, small amounts of radioactive material could conceivably be leached from the countertop into the food, although I cannot envision a scenario in which amounts would be high enough to cause any health problem.

Based on a large number of measurements that have been made in homes containing such materials, the added radiation dose that might accrue to typical home residents from exposures to these are not sufficiently high to produce any significant health risk or effects. The typical penetrating dose rate from granite countertops at a very close distance from the surface of the countertop is about the same as what we experience from normal background radiation on a regular basis. However, the dose rates drop off rapidly with distance from the material and the typical added dose that an individual receives in a year from ordinary use and direct contact with the affected materials would not add any statistically significant amount to the normal annual background dose that you already receive. Additionally, the short-term elevated background that one would experience in close proximity to a granite or other earth-based material surface, would be to very limited portions of the body, resulting in minimal dose to an individual.

I shall close with the assurance that your added dose from the presence of the cited materials is expectedly negligible, including the effects of breathing any radon released by the material (see this link to a position paper by the American Association of Radon Scientists and Technologists). I will include the added note, however, that inhalation of radon (and its subsequent decay products) is the largest source of natural background exposure to most individuals in the United States. Most of this radon comes from the radioactive decay of uranium and its radioactive progeny in the earth; the radon enters the typical home through cracks and other openings in the foundation structure of the house that contacts the ground. The US Environmental Protection Agency has recommended that homeowners should have their homes tested to evaluate radon concentrations. If you have not had your home tested for airborne radon, I strongly suggest that you have this done. Your state's radiation control agency may have test kits available. If higher than desirable levels are found, remediation methods can be successfully applied, usually at reasonable costs. This is one of the few practically controllable sources of background radiation exposure to the public, and evaluation is desirable since it is extremely difficult to predict the presence or absence of appreciable radon in a home without making measurements.

I hope the above is helpful to you and provides assurance that your earth-based products in your home do not present any significant health concern to you or your family.

George Chabot, PhD, CHP