Great discussion on granite countertop health risks.
Several points...
According to the researchers, it is looking like around 5% of granite countertop material types will have a radon problem in small, energy efficient homes. The problem is that a stone will be tested a dozen times and come up clean, then one is found that has elevated levels. Too much variety in the mineralization to predict. We have a radon room set up with 36 square feet of granite that is pumping out record levels of radon, see our forum for the details, look in the countertop material study section.
Bananas and smoke detectors having serious radiation are two common myths. One guy did manage to get a reading from bananas, he burned 100 pounds to ash, then measured the ash. I know that even a very sensitive meter will not detect any radiation other than background radiation if you stick in in a pile of bananas at Wal Mart. (Almost got thrown out doing that). Smoke detectors, a few of the guys on one of the radiation forums smashed up some smoke detectors, but the radiation will register only if the meter is a few millimeters away from the souce. At a few inches distance, you can't detect anything.
Cigarettes do have some radionuclides in them, but again it is tiny amounts close to what soil based radon would give you. The EPA says living with 4 pCi/L of radon in your home is like smoking a half pack of cigarettes per day.
On the bacteria aspect of granite, NASA has a cool study online, that found 100,000 bacteria per gram of stone. They proved that the bacteria were living and breeding inside the stone, using DNA testing of individual bacteria.
One thing that is just now coming out is the heavy metal aspects of granite. One researcher in California just found a countertop that had 10,260 ppm of Thallium present in one spot. To give you an idea of just how toxic Thallium is, if you had the weight of a postage stamps worth of Thallium, there would be enough to contaminate 570 workers to their maximum allowed exposure for an eight hour day. Here is a link to more info on that find
forum.solidsurfacealliance.org • View topic - Heavy Metal Data From a Granite Countertop
Lots of info on radon and radioactivity in granite on that site as well.
Anyway, great site, great discussion on the facts on these issues. Nice to see a civil discussion taking place on the issues.
Al