For many homeowners, granite is the countertop of choice, but could it pose a health risk?



Debate is simmering around the country about whether granite may emit potentially dangerous radon.



NewsCenter 5's Liz Brunner reported that a Texas physicist who tests granite slabs said there is no question there is a potential for risk. He said some slabs emit much more gamma radiation than what comes naturally from the ground.



"Especially when you have 100 square feet of it or 50 square feet of it in a kitchen," Rice University physicist William Llope said.



"What we can do is tell you that this countertop is more dangerous than this one," said granite salesman Al Gebhart.



Some granite salesmen nationwide go so far as to test what they sell.



"My position is that consumers ought to know that up front and let them decide whether to take it or not," Gebhart said.



They test for radiation as well as radon, a colorless, odorless gas that occurs naturally but which can cause cancer. Gebhart does his testing in sealed rooms.



The Environmental Protection Agency said a homeowner should take action if radon levels surpass 4 picocuries per liter. One room Gebhart tested showed an 8.1 but experts at the Marble and Granite Institute dispute sealed room testing methods.



"That's totally unrealistic. That has no basis at all. That should not be used. It's bad science," said John McCarthy of Environmental Health and Engineering.



McCarthy said a typical home kitchen has ventilation. The Harvard-educated scientist was hired by the Marble Institute of America and he tested 115 types of granite.



"We have not seen any data up to this point that would say there's a risk to anyone by having granite in their homes," McCarthy said.



The only way to know for sure if your granite counters may pose a risk is to test them. For $10 or $15 a radon kit will show you if your home is within EPA guidelines.



The Marble Institute is working to address concerns. They're in the process of coming up with a seal of approval that they hope will assure granite buyers that the stone has been tested and is safe to put in their homes.