Some granite countertops contain radioactive uranium ore. A homeowner with a radioactive countertops will be exposed to gamma radiation from the granite. However, inhalation of radioactive granite dust during installation is a far greater hazard.



Radioactive granite emits three types of radiation: alpha, beta, and gamma. Only gamma radiation penetrates the skin to enter the body. Gamma is also referred to as "penetrating radiation".



Alpha and beta radiation do not penetrate the skin, so they are not particularly harmful when they are outside the body. However, when radioactive granite dust is inhaled into the lung, the alpha radiation is extremely damaging to delicate lung tissue.



We became interested in the hazards associated with inhalation of granite dust when a fabricator asked us to monitor workers in his shop. We modeled inhalation of uranium dust, and our mathematical model predicted that uranium inhalation could exceed the Threshold Limit Value in some cases.



The air samples we collected in the shop showed considerably greater uranium inhalation than expected. Those data made a case for not relying exclusively on mathematical models. Actual exposure measurements found uranium inhalation was much higher than we expected.



We collaborated with a Certified Health Physicist, who calculated the total radiation exposure from the inhaled granite dust. Again, we were surprised. The health physicist calculated that our granite dust emitted considerably more radiation than the Nuclear Regulatory Commission would allow workers to breathe.



We presented our findings last week at the annual conference of the American Industrial Hygiene Association. The focus of the conference was on occupational hazards. However, granite fabricators occasionally do part of their fabrication in a client’s home. One homeowner told us that her "entire house was filled with dust".



A homeowner would be wise to require the fabricator to do cutting and grinding off-site, thus minimizing dust in the home. Any granite dust that is generated should be immediately captured with a HEPA vacuum.



Not all granite is radioactive. However, all granite contains large amounts of crystalline silica, which is also harmful to the lungs. It is not appropriate for homeowners to be exposed to the respiratory hazards that are present in granite.



If granite dust is introduced into the home, use damp wiping or damp mopping to clean hard surfaces. Launder draperies and other fabrics. A HEPA vacuum is the next best approach. Never use a conventional vacuum or dry sweeping to remove granite dust, as those methods will re-suspend dust in the air.