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Currently there is a buzz throughout the home improvement industry about granite counter tops.  Some, depending on where they have come from, are definitely radioactive in excess of background (there is always some radiation from cosmic and terrestrial sources present).  The reason for his is the presence of uranium, thorium and potassium 40.  These are all classified as Normally Occurring Radioactive Materials (NORM).  Al, at The Carpenter Shop, a local cabinet maker and kitchen fabricator, demonstrates the detection of radioactive granite here.  

Because of the areas that granite may be quarried, NORM content may be higher or lower.  Some granite that has been measured has no radiation in excess of background.  Other granite slabs may be quite radioactive.  Although in sufficient quantities radiation may not be the only hazard, decay products of uranium, radium and thorium that may be hazardous.  As uranium and radon break down, one of the decay products is radon 222.  Radon 222 is radioactive, colorless, odorless, tasteless and has a short half life.  Thorium in a similar decay chain will decay to radon 220, or what is commonly called thoron.  What is the problem with that?  As the two gasses are inhaled, they are also decaying to other radioactive elements, such as polonium 218, lead 214, that can stay in lung tissue and bombard it with alpha particles.  According to the EPA, it may be one of the largest causes of lung cancer, next to smoking.     

As for whether or not it is dangerous, and needs to be replaced, it all depends.  According to the EPA, if the Granites radon emissions bring your home over 4 picocuries of radon per liter of air, the answer is a definitive yes.  On the other hand, there are valid arguments by scientists that it may not be a health hazard in quantities that small. All sources agree, that Radon and Radiation are a hazard in large quantities, and that ingestion of radioactive material is hazardous, but as for small quantities, it may actually have beneficial effects.  There is growing evidence of a phenomenon known as radiation hormesis.  Radiation hormesis is an enhanced resistance to cancer or illness due to exposure to low levels of radiation.  Many doctors and biologists feel that it is the dose that makes the poison.  A good example of this is vitamins and minerals.  Vitamin A in the proper quantities is healthy however, if one ingests too much, it can be fatal.  Iron is also an essential mineral, however there are people that have died from an over abundance and have suffered the toxic effects and even died.  As far as studies there have been very few though, a good example is the Nuclear Shipyard Workers Study.  Indications are that Nuclear shipyard workers tend to live longer and healthier than those who work at normal shipyards.  Other indications are in health demographics found in he United States.  People living at higher altitudes tend to live longer healthier lives than those living at lower altitudes receiving less radiation.  Unfortunately there are many other factors which may be at play, so it is highly unlikely that there will be any definitive studies in the near future.       

The only way to tell if your granite is radioactive is with a geiger counter, ion chamber or scintillation detector.  It will not glow or buzz to warn you, it will not give any indication that it is radioactive.  If it is radioactive, then you may want to get a Radon Test Kit, which is available at any hardware store.  A special note, if your counter top is radioactive, it does not mean it emits radon.  Radium and Thorium will emit radon and or thoron as a waste product,  however, uranium and potassium will not.  The content of of all these radioactive substances does vary widely.  


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