Granite countertops may give off a small amount of radon; a colorless, odorless, tasteless gas that, in high concentrations is known to cause cancer. However, the amount that is given off from granite countertops is negligible compared to the amount given off from soil underneath homes. There are a number of misleading articles on how to accurately measure the radon given off by a countertop, and most experts agree that granite countertops in today’s kitchens pose no risk to human health.
Radon Levels
Radon is the leading cause of lung cancer among non-smokers. It is the second leading cause of lung cancer in America, causing about 20,000 deaths per year. However, even if granite countertops emit a small amount of radon, according to the EPA, “in the United States, radon gas in soils is the principal source of elevated radon levels in home.”
In fact, natural granite countertops are not the only source of radon to which people are exposed. All natural products contain radioactive elements that sometimes emit radon and can also emit measurable amounts of radiation. Concrete, sand, clay, non-plastic dishes, coal, silica glass used in eye glasses, mirrors, windows and even phosphate fertilizers and the vegetables grown in those fertilizers, contain potassium and small amounts of uranium and thorium.
Information Bias
There is inherent bias in the sources for the various statements as to whether or not granite countertops pose a health risk. The allegation that granite countertops may emit dangerous levels of radon and radiation have been made mostly by the makers and distributors of competing countertop materials. Conversely, the suppliers of granite used to make granite countertops, such as the Marble Institute of America claim that the radon amounts in countertops are not enough to pose a health threat.
Health physicists admit that granite countertops do emit radiation and radon in low levels. However, these emissions are thought to be insignificant compared with background radiation levels from natural sources such as space, soil and manmade sources such as X-rays, luminous watches and smoke detectors.
Granite Colors
Different colors of granite countertops appear to emit different amounts of radon. Reds, pinks and purples found in granite countertops often appear to emit more radon gas and radiation than other colors.
Measurements
The amount of radon gas emitted from a granite countertop can be measured and there are many kinds of low-cost radon test kits available to test radon levels. Testing cannot be done by placing a container of unknown volume on the countertop for a particular time. Testing devices are only calibrated to measure radon captured from a known volume for a specific amount of time. It is also important to test radon levels at multiple locations not only to determine potential hot-spots on the countertop, but also to determine the background radiation or radon emission levels not related to the countertop.
Geiger counters are devices designed to detect radiation levels and report them audiologically; the more clicks heard, the higher the radiation detected. However, they are misleading. Hand-held Geiger counters are not calibrated for measuring only radon-producing radium in granite. They will over-respond because other sources of radiation, such as potassium and thorium are also measured simultaneously. Professional grade radiation detectors of the type used in hospitals and nuclear power plants are more accurate than the pancake Geiger counters typically used.
Exposure Risks
Dr. John McCarthy, president of Environmental Health & Engineering, indicated air dilution plays a critical role in measuring radon levels. He states, "To properly measure radon, one must calculate the emission rate in connection with the area of granite and the volume of air in the home." Radon will dilute in home air. He further states that you would have to completely seal off the room containing the granite countertop and stay in that room 24/7 for 72 years to get even slightly close to dangerous levels of radon exposure. A more typical exposure to a kitchen granite countertop would only increase cancer risk by one in two million, compared to the risk of three in ten-thousand of contracting cancer from normal background radiation.
