FACT - Granites often contain trace amounts of material that can produce measurable amounts of radon gas.
However, the key word is
"measurable". As an illustration, imagine turning on a burner on your stovetop. The burner emits heat, but has little to no effect
on the overall temperature of your house. Similarly, if your countertop emits a small amount of radon, it will generally be insignificant
when diluted with the quantity of air in your entire home.
You are hundreds of times more likely to be at risk for radon emanating
from the soil beneath your home. The US EPA states it simply in the Consumer's Guide to Radon Reduction:
"In a small number of homes,
the building materials (e.g., granite and certain concrete products) can give off radon, although building materials rarely cause
radon problems by themselves. In the United States, radon gas in soils is the principal source of elevated radon levels in homes."
I still want to test my countertop. What should I do?
Many methods for testing granite countertops have been suggested recently. Unfortunately
most of these involve using radon test kits for something they were not designed to do.
One of the more common suggestions has been
to place a radon test kit in an inverted bucket or large bowl and place it on your counter top for the duration of the test. We do
not recommend this method. While it may give an indication of whether or not the countertop is emitting radon, it does not provide
you with an overall assessment of your indoor radon risk. A test using the "inverted bucket" could easily generate a relatively high
reading of 20 pCi/L and yet the countertop itself could present almost no risk to you. Why? There is an incredibly small volume of
air within the bucket when compared to the entirety of your home. What generates 20 pCi/L in a bucket would most likely contribute
only a tiny fraction of that amount to your overall indoor air levels.
While the "inverted bucket" method bucket may tell you that
your countertop is generating some radon gas, it does not present you with any useful information as to how much radon is in your
home. A better methodology would be to concurrently perform additional tests in the lowest livable area of your home and the area
of the suspect material. If the results of your indoor radon levels in both areas are substantially similar the granite is not likely
having a measurable effect on your indoor radon in air levels. If the levels of radon in the area containing the granite are higher
than your indoor levels in another area of your home then it is possible that the granite is contributing to, or is the source of,
your indoor radon levels.