“Quantities of radon and radiation emitted by stones included in the analysis all fell well below average background levels commonly found in the United States,” the institute said.

The study included more than 400 tests of 115 different varieties of granite countertops — including stones cited in media reports as being potentially problematic, the most common types of granite used in countertops in the U.S. and the more exotic stones that represent a tiny share of the market. The types of stones tested comprise about 80% of those used in domestic countertops.

The study found that:

• Not one stone slab contributed to radon levels that even reached the average U.S. outdoor radon concentration of 0.4 picocuries per liter — one-tenth the U.S. Environmental Protection Agency level for remedial action within a home.
  
  The stones found to emit higher radon levels — though still well below average outdoor background levels — represent less than 1% of U.S. granite countertop sales.
  
  
• Not a single stone emitted radiation levels that even approached a radiation dose of 0.13 milliSievert per year, the level determined by the European Commission to be negligible for human health risk; the U.S. has no such standard. However, this European standard is just 30% of the 1 milliSievert per year annual dose limit recommended for the general public by the National Council for Radiation Protection & Measurements.

“Unlike some media reports of questionable scientific accuracy, this study evaluated a large variety of stones and used a number of complementary, well-established scientific techniques to assess the exposures that people could have to radon and radiation in real-world environments and to determine whether the presence of these specific stones could compromise consumer health,” the Marble Institute said.

“Our study included detailed mapping of radiation emitted from various stones that had areas that we identified as being elevated above levels for typical granite countertop material,” said Dr. John F. McCarthy, president of Environmental Health & Engineering, the independent environmental testing firm that conducted the study.

“We found that it’s easy to get what appear to be high readings of radon or radiation from a small fraction of granite countertops, but those readings do not reflect the actual risk to consumers because they do not assess the real exposure, only isolated, extreme measurements,” he said.

“As with any other type of environmental measurement, assessing the real risk to consumers must take into account more than isolated readings from small spots on a countertop,” McCarthy said. “It must reflect real-world exposure scenarios and be interpreted using well-established principles of environmental health.”

For more information on this issue from NAHB, e-mail Ken Ford, or call him at 800-369-5242 x8228. [return to top]