Test.
Granite Countertops.
Radon can enter your home's indoor air in four different ways:
• Degassing from water - radon can readily dissolve in groundwater and can enter the home through the water supply; as radon degasses from water, it can enter the air (on average, 10,000 pCi/L in water adds 1 pCi/L in air)
• Diffusion - radon diffuses from the soil through the slab due to concentration gradients (high concentration to low concentration)
• Emanation** - building materials within the envelope of the building can contain uranium or radium, and radon can emanate from the surface of the material (i.e. granite)
Radon can emanate from granite materials in your home, but generally at very low levels.
In some homes, building materials (i.e. granite and certain concrete products) can be a source of radon gas. According to the EPA, it's possible for any granite sample to contain uranium and other naturally-occurring radioactive elements. Such elements can produce radon gas, thus granite used for countertops may variably contribute to indoor radon levels.
While natural stones can emit radon, the EPA does not believe that sufficient data exists to conclude that the types of granite commonly used in homes are significantly increasing indoor radon levels. However, measurement of specific samples can reveal higher than expected radon levels on a case-by-case basis.
Comparison testing.
Currently, no widely-accepted radiation testing protocol exists for granite countertops, and no radiation testing is required on granite products. According to the American Association of Radon Scientists and Technologists (AARST), direct measurement of radon emanation from a material such as granite is not a reliable indicator of the radon levels in the air you breathe. Such measurements are subject to large errors in estimating risk due to the variability of emanation rates, the variability of ventilation rates, and the volume of space where the material is contained.The best assessment of your radon health risk is to test the air you breathe. Although not specifically designed for measuring radon emissions, multiple continuous radon monitors can be used to conduct diagnostic testing. One monitor would be set up under normal protocols, and another monitor would be placed in a room containing the granite countertop.
While such testing would not definitively identify the source of radon, it's useful in comparing radon levels in different areas of the home, including areas with granite countertops or other radon-emitting materials.
Minimize health risks by reducing your exposure.
The best thing you can do to minimize the potential health risks is reduce your exposure to radon gas.
If you want to take measures to reduce the radon levels in your home's indoor air, the most effective way is Active Soil Depressurization. If you compare the enormous surface area of the soil underneath the foundation to the surface area of a solid piece of granite, you can see how on average 90% of indoor radon comes from the soil. In most cases, limiting the flow of radon from the soil will reduce radon levels well below the 4.0 pCi/L EPA Action Level.
To further reduce your exposure to radon, you can increase the ventilation rate of your home. The contribution from building materials to the indoor radon level is highly dependent upon ventilation. Increasing the fresh air make-up of a building can dilute radon and other indoor contaminants. It can also reduce the negative pressure of a building, and therefore reduce the entry of radon.
Only as a last resort would the removal of granite be necessary for reducing indoor radon levels.
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Radon in Your Home's Indoor Air Our Testing Process
Radon in Granite Understanding Your Test Results
Radon in Water
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