Are Granite Floors and Countertops Safe?

What Experts Say and How Granite Poses Health Risks in Your Home

Oct 1, 2009

Polished granite is a luxurious, durable construction material that adds considerable value to a home. But experts say it can also increase one's risk of lung cancer.

In July 2008, granite countertops received media attention regarding their potential to emit radon gas. Radon is a radioactive colorless and odorless gas produced by the degradation of uranium, a radiant energy emitting element. Radon - 222 (Rn) and its breakdown products, polonium 218 and polonium 214, are radioactive gasses that emit alpha particles which can damage lung tissue when inhaled, which is of the causes of lung cancer.

Nature and Geographic Distribution of Radon

Radon (Rn) is a radioactive gas that is formed by the natural decay of uranium (Un). It is found in water, rocks like granite, crystals such as germanium, and soil. Any naturally found rock material has the potential of containing varying amounts of naturally occurring radiation. Because radioactive elements like uranium, radon, and thorium can be present in a wide number of materials that appear as crystals in granite, it is not unusual for these rocks to have some amount of radioactivity. Depending on the composition of the molten rock from which they were formed, some pieces of granite can exhibit more radioactivity than others.

Nature and Economic Use of Granite

Granite is an igneous rock formed by the slow cooling and crytallization of magma (molten rock) at some depth in the earth's crust. Because granite develops over thousands or millions of geologic years, the minerals it contains take even longer to crystallize. They give granite a variety of colors and luster. Owing to its great crushing strength, resistance to weathering, and ability to take on a high polish, granite is widely used as an ornamental stone both in the interior and exterior of buildings, hardscaping in gardens, and for monuments. In the home, it has been historically used as wall and flooring material, countertop covering, retaining walls, garden furniture, etc..

Legislations About Radon Emissions from Granite Countertops

Currently, the U.S. Environmental Protection Agency (EPA) has not conducted studies on the radioactivity of granite countertops. However, the EPA believes that most types of granite used in countertops are not the major contributors of radon radiation in the home. Because granite is not very porous (full of tiny holes), the EPA believes that less radon is likely to escape from the stone. Also, kitchens and bathrooms are typically well ventilated areas, so the amount of radon emissions are more likely to be "dilute". If the air in your home has radon levels of 4 picoCuries per liter (pCi/L) of air or more, you should contact your Radon Office for assistance at 1-800-SOS RADON (767-7236). Radon levels in the home should be reduced to less than 2pCi/L. The agency promises to monitor evolving research and provide pertinent public information.

Health Canada has established guidelines and recommends that action be taken when the concentration of radon emissions exceeds 800 Bq/m3 although they are proposing a new guideline that Bequerel levels should be reduced to 200 Bq/m3. Radon is measured in Bequerel units per cubic meter. Bequerel (Bq) is the activity of a quantity of radioactive material. It is expressed in the System Internale Unit (SI) used in Europe, Canada, and other countries in the world. Health Canada's contact agency is the Radiation Protection Bureau in Ottawa, Ontario. Their toll-free number is: 1-866-225-0709.

In Europe, the European Union recommends that action should be taken starting from concentrations of 400 Bq/m3 for "old" houses, and 200 Bq/m3 for "new" homes.

Reducing the Risk of Radon Emissions in Your Home

In Canada, the Radiation Protection Agency suggests that you take action if the normal levels of radon emission is greater than 200 Bq/m3 (Bequerels per cubic meter). The higher the readings, the sooner your response should be. After testing, reduce radon emissions to values as low as possible. Install radon detector devices to monitor radon emission levels. Note: Radon detectors are exposed to the air for a period of time just like smoke detectors. After the allotted time period, it is sent to a laboratory for analysis.

References

Myatt TA et al. "Assessing Exposure to Radon and Radiation from Granite Countertops" Health Physics November 21, 2008;46(6):1195-1203

Allen JG et al. "Assessing Exposure to Radon and Radiation from Granite Countertops - Part 2 Radon"

"Granite Countertops and Radiation" Radiation Protection U.S. Environmental Protection Agency Website

"Requirements Related to Radon Exposure" European Commission Services Considerations with Regards to Natural Radiation Sources in BSS Directive January 16, 2009

The copyright of the article Are Granite Floors and Countertops Safe? in Public Healthcare Issues is owned by Alicia Richardson. Permission to republish Are Granite Floors and Countertops Safe? in print or online must be granted by the author in writing.