In June, a nationwide advisory cautioned that granite fabricators can be exposed to more radiation than nuclear power plant workers. The data behind that advisory were presented at the Health Physics Society annual conference this week. Those data show that granite fabricators can be exposed to several hundred times more radiation than allowed by the Nuclear Regulatory Commission.



The granite used to collect the data was Jupurana Bordeaux, removed from a San Carlos home last fall. When Cathy Woods learned that her counter tops qualified as uranium ore, she had her granite removed. Cathy generously allowed us to use that granite for research.



We shipped samples of Cathy's granite to scientists around the country. Those scientists tested her granite for radiation, radon, and thoron emission. Their data will be presented in papers they publish over the coming months.



We used other sections of Cathy's granite to measure uranium exposure during fabrication. When we saw the lab reports, we had some concerns. The airborne dust in the work area contained more uranium than OSHA would allow.



However, radiation exposure was a far greater concern than just uranium inhalation. Uranium decays into a series of other radioactive isotopes. Each of those isotopes is present in granite, and each isotope contributes to the total radiation exposure.



The Nuclear Regulatory Commission limits licensed radiation workers to a dose of 5 rem/year. Data from Cathy's granite indicate that granite fabricators could be exposed to several hundred rem/year. However, granite fabricators are not licensed, trained, and monitored radiation workers. It is more appropriate to place granite workers in the category of the general public.



The Nuclear Regulatory Commission recommends that members of the public limit their radiation exposure to just 0.1 rem/year. Granite fabricators could be exposed to several thousand times that limit.



If they chose to do so, granite importers could scan granite at the source quarries and remove radioactive stone from the market. Until the industry takes the needed precautions, granite fabricators can scan granite themselves and refuse to fabricate radioactive stone. A few shops have already taken this step.



Granite fabricators need to keep their shops immaculately clean and free of granite dust. Use wet fabrication processes whenever possible. Capture dust with HEPA filtration. Dry sweeping can re-suspend settled dust, so use only wet mopping or HEPA vacuums to clean shop floors and work areas.