Marble Institute of America: Industry and Professional Resources - Technical Bulletins: The Truth About Granite & Radon/Radiation 9/2005

Radon in Granite - Comments from Leading Experts

Over the past few years there has been some consumer confusion about rumored radiation levels occurring in natural granites used for residential countertops, floors, tiles, etc. Unfortunately, the origin of these concerns are advertisements and other communications from the manufacturers of radon detection devices and the producers of competing materials.

A number of sources have commented on this subject:

In a small number of homes, the building materials (e.g., granite and certain concrete products) can give off radon, although building materials rarely cause radon problems by themselves. In the United States, radon gas in soils is the principal source of elevated radon levels in homes.
– Environmental Protection Agency – Consumer’s Guide to Radon Reduction
“I believe that is reasonable to say that the materials (granite) tested pose no significant radon risk….the radon contribution from a typical countertop installation is less than 1% of the concentration found in the average U.S. home”
– Daniel J. Steck, Ph.D., Professor of Physics, St. John’s University
– This assessment was made based on a series of tests conducted on a variety of granites compared with the typical values of a number of other building products including concrete, brink, gypsum and cement. These test results were also applied to a computer model assessing two kinds of installations (70 square feet typical of a counter-top treatment and complete coverage of walls and floors) were considered in three types of houses; an average house; a large, airy house; and a small, tight house.
“The amount of radon from a granite countertop is insignificant compared to the radon in the vast quantities of soil and concrete people are exposed to on a daily basis.”
– William B. Size, Ph.D., Interim Chair, Department of Environmental Studies, Emory University
“Granite, as with all other kinds of rock and soil, contains some naturally occurring radioactive elements including thorium, uranium, and potassium-40, a radioactive isotope of potassium. However, generally speaking, the amount of radioactivity in most granites is quite small, amounting to a few tens of parts per million at the extreme. While it is possible to get a measurable level of external radiation from some granites (most notably Grand Central Station in New York City), the levels are so low as to not be harmful to human health. So enjoy your new house with its granite kitchen countertop (which I suspect is quite beautiful) without worry or fear from health hazards from radioactivity in granite.”
– Ron Kathren, CHP, Health Physics Society
“…the concentration of radon that is given off by the countertop into household air is 0.00000074 pCi/L, an amount that is 270,000 times less than the level of radon in outside air!”
– Donald Langmuir, Ph.D., Professor Emeritus of Chemistry and Geochemistry, Colorado School of Mines
– Standard scientifically accepted models and conservative assumptions were used to apply field test values for an average ventilated house. The worksheet used was published in the Granite & Radon – The Truth special bulletin by the Marble Institute of America