According to a study, Granite countertops may pose a health risk by emitting radioactive gas which can cause cancer. The unpublished study was reported in the New York Times. Rice University physics Professor W.J. Llope asserted that granite countertops, a popular staple in the homes of many people in the U.S. and abroad, give out dangerous radon fumes and gamma radiation, due to their uranium content. He stated that while many stones out of the more than a thousand varieties of granite sold in the United States are not radioactive, but a few really are and none of them is routinely tested for radioactivity.

Professor Llope tested 55 stones of differing types of granite bought from dealers in and near Houston, Texas. He found that a few of those emitted a gas which could expose homeowners to 100 millirems of radiation in a few months, this amount is the annual exposure limit set by the U.S. Department of Energy for visitors to nuclear labs.

Granite, an igneous rock formed from Earth's solidified magma, is popularly used in construction because of its high quality, and size, as well as the fact that it is very tough.  It contain around 10 to 20 parts per million of uranium, and as radon gas is heavier than air it is known to linger in basements sunk into the ground. Radon is radioactive noble gas that is formed from the decay of radium. It is considered as the second most frequent cause of lung cancer, after cigarette smoking, and allegedly causing 21,000 lung cancer deaths in the U.S. every year.

The Marble Institute of America called Professor W.J. Llope's findings "junk science." They issued a statement which alleged that U.S. Environmental Protection Agency (EPA) statements reaffirm that granite countertops are safe and have no significant health risk for users.

In a statement the EPA said that granite countertops emitted a radioactive noble gas, radon which has no taste, no odor etc. “While natural minerals such as granite may occasionally emit radon gas, the levels of radon attributable to such sources are not typically high. EPA believes the principal source of radon in homes is soil gas that is drawn indoors through a natural solutioni process.”

Finland, Norway and Sweden, northern Portugal, Spain, Brazil, India and several countries in southern Africa, namely Angola, Namibia, Zimbabwe and South Africa have most of the granite quarries.

The EPA in their statement said that construction materials like granite, concrete, cinder blocks etc can contain small radioactive materials. The report said people who have granite countertops in their homes should get them tested for radon.