Radiation test on granite countertop leads Llope to broader issues

TV request turns into new hobby for nuclear physicist
Radiation test on granite countertop leads Llope to broader issues

BY JADE BOYD
Rice News staff

An afternoon detour to help a local TV news crew last month has turned into a scientific odyssey for Rice nuclear physicist Bill Llope.

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Llope, of Rice’s Bonner Nuclear Laboratory, was approached in late April by KHOU Channel 11 news reporter Lee McGuire to verify whether some granite kitchen countertops might be emitting dangerous levels of radiation.

“I was asked to test the natural stone countertops in a home with a Geiger counter,” said Llope, faculty fellow in physics and astronomy. “In five specific locations on the countertops, the radiation emission was alarming.”

Later, he measured the spectrum of gamma radiation emanating from a section of the same countertop featured in the KHOU story. The data, collected on campus, indicated the presence of uranium ore, with traces of other radioactive nuclei, namely potassium and thorium.

His curiosity piqued, Llope searched for peer-reviewed studies that would shed light on what he had found. Llope located about 20 peer-reviewed articles containing data from around 100 samples. In contrast, one online marketplace for residential counters listed 1,600 varieties of granite from 64 countries.

“Some peer-reviewed science is available, but it doesn’t cover the wide range of material available for residential use,” Llope said. “Moreover, direct measurement of the stones being sold in homes doesn’t really exist.”

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Llope said there are two primary radiation dangers from countertops: They can emit direct radiation, and they can give off radon gas.

Llope said the available evidence suggests there are minimal radiation risks from most granite. However, there’s no way to know whether the available data actually applies to the stone being sold for residential use, and Llope said there’s clearly a need for more testing of stones that are intended for home use.

Llope said what started as a routine request for help from a reporter has turned into a new hobby. He’s created a Web site with details of what he’s learned so far, and the site has gotten tremendous traffic from the U.S., Asia, Europe and Australia in the wake of his television appearance.

Llope said he’s interested in collecting more data on stones that are being sold for residential use. He is collecting additional samples of well-identified stones that are available for installation in U.S. homes both from Houston-area dealers and elsewhere, and he will measure the radiation rate and spectra from each.
 
“Both the granite industry, and it’s competitors have a stake in this,” Llope said. “I’m coming at this from a purely scientific perspective, and I’m unaffiliated in any way with the granite industry or its competitors. I’m all about the data.”

Llope said he’s participating in a few home improvement forums on the Internet to make his results better understood to the general public.

His analysis of the existing literature and test data is at http://wjllope.rice.edu/saxumsubluceo/.