Granite and Radon
Recent media attention has focused on granite countertops and whether they can increase your indoor radon levels. While testing your home is always a good idea, a few clarifications are in order.
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?
You can order an activated charcoal Complete Granite Counter Top Test Package on our online store.
Why Geiger Counters will not accurately measure radon
Most web videos and TV demonstrations measure the granite counter top using a Geiger Counter. These simple audible devices are being used for dramatic effect and are misleading in two principle ways:
1. Simple hand-held Geiger Counters are not calibrated for measuring ONLY the radon-producing Radium in granite. This means they will almost always over-respond when attempting to measure the radon emissions.
2. Not all the radiation coming from the granite that makes the clicking sound comes from radon-producing Radium. In most cases the noise is produced by two other naturally occurring elements: Potassium and Thorium. In fact, up to 80% of the Geiger Counter clicks may come from the Potassium. Potassium is very common and is found in our own bodies, as well as many foods (e.g., orange juice) and vitamin supplements.
FACT: Potassium does not produce any radon gas.
Thorium produces a different type of gas called Thoron. Thorium is a shorter-lived element, which is similar to radon but decays about 6,500 times faster than radon. Thoron has a half-life of about 51 seconds, whereas Radon has a half-life of just over 92 hours. Because most of the Thoron never makes it very far from the granite's surface, the US EPA does not consider Thoron a major contributor to health problems.
The bottom line. Gamma measurements made with simple hand-held meters have absolutely no relationship to potential radon emissions. Therefore, simple gamma measurements cannot be used to definitively determine if your granite counter top is safe. Only very expensive portable instruments are capable of separating the actual radon emissions from other radiation producing elements. A much simpler and lower cost method is to use activated charcoal to sample the radon and thoron gas, which then can be analyzed with sophisticated laboratory equipment that is able to determine if there is a potential radon problem coming from the granite.
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 (What is a pico curie?) 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.
Why the proposed "Inverted Bucket" method will not accurately measure for radon
The Inverted Bucket method suggests placing any radon test kit under an inverted bucket or large bowl and leaving it on your counter top for the duration of the test. While it may give an indication of whether or not the counter top is emitting radon, it does not provide you with an overall assessment of your indoor radon risk unless the lab knows the exact volume of the exposure container, as well as the surrounding indoor air levels. Additionally, the lab needs to analyze the sample specifically looking at the radon levels ONLY!
FACT: Most labs do NOT discriminate between radon and thoron levels in the sample.
That's why it's important to (1) use a test where the laboratory knows the EXACT exposure volume and (2) simultaneously perform additional tests in the area of the granite counter top and in another area at least 20 feet away. If your indoor radon levels in both areas are substantially similar, the granite likely does not have 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 AND the counter top test device also returns a high result, then it is possible that the granite is contributing to, or is the source of, your indoor radon levels.
* - The US EPA encourages you to consider reducing your radon levels for readings between 2 and 4
You can order a Complete Granite Counter Top Test using using our secure online store.
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