Rice University physics Professor W.J. Llope alleges that according to his yet unpublished research, some granite countertops found in U.S. homes give out dangerous radon fumes and gamma radiation, due to their uranium content. While most stones are not radioactive, a few are, and it appears that nobody tests them.

Professor Llope tested some 55 stones of more than two dozen types of granite bought from dealers in and near Houston, Texas. A few of those could expose homeowners to 100 millirems of radiation in a time span of a few months, which is the annual exposure limit set by the U.S. Department of Energy for visitors to nuclear labs.

Of the more than a thousand varieties of granite sold in the United States, none of them is routinely tested for radioactivity. Meanwhile, Marble Institute of America rushed out a statement which alleges that U.S. Environmental Protection Agency (EPA) statements reaffirm that granite countertops pose no significant health risk.

The Environmental Protection Agency says radon gas in homes comes mostly from soil gas that is drawn indoors through a natural suction process. The government regulator said that most construction materials made from minerals contain various small amounts of radioactive substances.

The Marble Institute of America also called in the statement Professor W.J. Llope's findings "junk science."

Granite is a high-quality construction material because it is nearly always massive (lacking internal structures), and is very tough. It is an igneous rock and formed from Earth's solidified magma. It is known to contain around 10 to 20 parts per million of uranium. It seems that there is some concern for buildings located over granite, as radon gas is heavier than air and is known to persist in basements sunk into the ground.

The chemical element Radon is radioactive noble gas that is formed from the decay of radium, and some sources allege that it causes 21,000 lung cancer deaths per year in the United States alone and is thought the second most frequent cause of lung cancer, after cigarette smoking.

Most granite quarries are located in Finland, Norway and Sweden, northern Portugal, Spain, Brazil, India and several countries in southern Africa, namely Angola, Namibia, Zimbabwe and South Africa.