There was for at least a time a major concern about granite counter tops and radon gas exposure. The truth is, there really is only a small amount of radon gas emitted from granite, but normally the amounts are so low that they do not present a danger. It’s also true that there was a counter top war happening and the makers of certain types of resin-based counter tops were causing the granite mining industry some trouble by pointing out the higher radon emission levels of granite. Personally I just consider it a marketing strategy due to the popularity of granite and a drop in resin-based counter top sales.
The primary health risk of exposure to radon gas is lung cancer. Your lung cancer risk is determined by the amount of radon you are exposed to, and how long you are exposed to it. At least at one time the Surgeon General was claiming high exposure to radon posed a real health threat. They have removed their press release from the internet, but the claim was made. The EPA still claims it is the second largest cause of lung cancer.
The average radon gas level in homes across the U.S. is about 1.5 picocuries per liter (pCi/L). Because no amount of radon is considered absolutely safe, measures should be taken to lower the amount of radon in every home. You should definitely take action immediately if the annual average level is higher than 4 pCi/L. You can perform short and long-term tests in your home and tests can be purchased online here.
According to this Florida State Department Of Health web site, never has a radon mitigation company ever recommended the removal of a granite counter top as a remedy for high radon levels in a Florida home. That speaks volumes for the entire country, since no two homes will necessarily get the same results from any test performed, nor is it true that if your neighbor tested high (or low) that your home will test the same. That fact points to numerous possible causes for high levels in your home.
In my past research, I also learned that certain colors of granite have higher emissions than others. For example, reds and purples tend to emit more radon gas than, say, beige or yellow colored slabs.
In some cases you can treat the problem of high radon levels in your home yourself, but you should always consider contacting a trained radon reduction contractor. You can call your State Radon Office to locate a contractor, and also request a homeowner’s guide.