I was just reading Todd Clark's blog where home buyers did not want to purchase the home because it had granite counter tops. The buyer said that granite can give off radon. At first I thought it was one of those urban legends or an exaggerated tale that happens one in a million, but the dangers may not be so far fetched.
The Marble Institute of America reports that “radon is a naturally occurring gas generated by the decay of trace amounts of uranium found in the earth’s crust throughout the world. It is an unstable gas that quickly breaks down and dissipates in the air.” 
In 2008 the Marble and Granite Institute of America conducted their own study and found granite counter tops do emit radon and some colors have a higher change of radon leakage than others. Crema Bourdeaux has the highest radon levels followed by Tropic Brown and Baltic Brown. Most manufacturer will say that these gasses will be dissipated by the home's ventilation system. As you can imagine the debate of the safety of granite counter tops in the home gets pretty heated. You can read the study HERE in PDF format.
All natural products, especially stone, minerals, and sand, contain trace amounts of some radioactive elements called NORMs (Naturally Occurring Radioactive Mineral) that can produce measurable amounts of radiation and sometimes radon gas. It has been said that there is no more threat from granite than from the air outside. Read article.
If you are planning on installing granite counter tops in your kitchen you can check with the manufacturer. Many are advertising radon free counter tops. If you already have granite counter tops in your home you can purchase a kit to test the radon levels. There are several available on the market.
When it comes right down to it I think people could find a possible environmental threat almost anywhere.
This subject is fairly new to me so if you have any more information or opinions I'd love to hear them.
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