There is an aspect to granite that many homeowners and businesses never think about that could impact indoor air quality. Granite is a natural rock material. It is classified as an igneous rock, which means it was formed by fire. In this case, by fire, we are talking about lava. The granite started off as molten rock which has cooled and solidified over thousands of years; in some areas over millions of years. Because of the slow process of forming granite, crystals form at various stages which creates the desirable patterns. Being a rock material from the earth there is the possibility that naturally occurring radon can be released from the granite. That is right, radon could be emitting from your countertops!
Radon from countertops is not a particularly new phenomenon but interest and concern increased after an article was published by the New York Times in July of 2008. The public’s concern grew as awareness of this potential risk became commonplace and more people were looking to have granite installed in their homes.
The reason radon can be released is that many rocks contain naturally occurring radioactive elements like radium, uranium and thorium. Each piece of granite is different; therefore it is impossible to know exactly how much radon is being emitted. The amount of radon is dependent on the level of radioactive elements present in the specific piece of granite.
If these radioactive elements are present in the granite in your home they will decay and create radon gas. Radon is a colorless and odorless gas that cannot be detected without special instrumentation or laboratory analysis.
Breathing in radon gas and its byproducts is known to significantly increase the risk of lung cancer. As with most exposures the risk is dependent on many variables such as concentration and the amount of time that the exposure occurs for. The EPA recommends that exposure to radon gas be minimized as much as possible.
The big question remains; are granite countertops a significant risk for exposure to radon gas? According to the Environmental Protection Agency (EPA) granite is a dense material therefore it is difficult for radon gas to emit into the open air. Rock material that is porous, such as sandstone, will more readily release radon gas.
The EPA and the American Association of Radon Scientists and Technologists (AARST) both agree that the risk of radon overexposure due to granite countertops, at this time, is low. Further, the EPA states that …”existing data is insufficient to conclude that the types of granite commonly used in countertops are significantly increasing indoor radon levels”. The main reason this conclusion is made is that the emission rate is slow and the ventilation in a kitchen is generally good.
The EPA and Surgeon General do recommend that all homes be checked for radon gas levels. The major source of radon in homes is the soil surrounding the basement floors and walls. At EPA's action level of 4 pCi/L, a smoker's risk of lung cancer is about five times the risk of dying in an auto accident, and if you've never smoked equal to the risk of dying in an auto accident. It should be noted there is no standard or approved way to evaluate radon or radioactive emission rates for countertops. Testing your home for overall exposure is the best approach at this time.
Another issue is if the particular piece of granite contains a higher concentration of radioactive elements then there is risk of gamma radiation exposure. As with radon, the risk appears to be low from available study/literature review. The EPA is continuing to evaluate information regarding radon and radiation levels from granite countertops.
In conclusion, the current information states that radon gas is emitted from granite countertops but typically at a level that is not going to create an overexposure issue in the home. The main exposure concern to radon is the soil surrounding the foundation. Regardless if you have granite countertops or not it is strongly recommended that your home is tested for radon levels. There are many self-service test kits available to screen your home.
To learn more about radon in your home please check the information at the EPA web site: http://www.epa.gov/radon/