Radon Gas, An Over Reaction?

Granite is an igneous rock, which is formed when magma cools very slowly.   This process can take many thousands of years.   

During this time minerals grow into the crystals that give granite its various colours. Within these crystals, elements like uranium, radium, and thorium may be present.  

These radioactive materials are found in all kinds of rocks and soils.   The radiation given off by these materials in nature, is all mixed up into "background" radiation. Background radiation is a combination of terrestrial and cosmic radiation that individuals are continuously exposed to.

Like all naturally formed rock, granite may contain naturally occurring radiation.   Over time these naturally occurring materials may decay into Radon gas.   Radon is  a colorless, odorless, radioactive gas.    However, based on the information available the EPA (US Environmental Protection Agency) believes that most types of granite used in countertops are not major contributors of Radon in the home.   

Levels of radiation and Radon Gas are technically measurable, but are in fact small fractional values of established thresholds for environmental safety.  "Since granite is generally not very porous, less radon is likely to escape from it than from a more porous stone such as sandstone.  It's important to know that radon originating in the soil beneath homes is a more common problem and a far larger public health risk than radon from a granite countertop or other building materials. Also, any radon from granite in kitchens or bathrooms is likely to be somewhat diluted in the typical home since those rooms are among the most ventilated."    ¹

If we look at the typical contributors to radon contend of indoor air ( pCi/L), we start to get a better picture.  The major contributors by percentage are Soil around the house 69.3%, Well water 18.5%, Outdoor air 9.2%, building materials 2.5%, and Public water supplies 0.5%.

In fact the EPA has stated that they are much more concerned about levels of radon seeping into homes, through the basement floor.

Looking specifically at granite counter tops, we will find that the amount of radon gas given off is 270,000 times less than the level of radon gas in the outside air.    ²

So what can you do if you're still concerned?  To reduce your risk of exposure to radon, the EPA recommends that you test the air in your home.    There are many inexpensive do-it yourself home radon test kits available in stores.  Or, you could just open the window.  If you have a well built, properly ventilated home, radon should be the last of your worries.    

1 - US Environmental Protection Agency
2 - Marble Institute of America, Technical bulletin 2007.