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January is National Radon Action Month. Californians can get a free test kit here


While there are many natural hazards that are commonly discussed in the San Jose area, such as earthquake faults, flood planes, and liquefaction zones, there’s one which comes up frequently on the east coast but is largely ignored here in the Valley of Heart’s Delight. The question is this: is there a radon risk in Silicon Valley  homes?
Radon is a colorless, odorless gas - what is the risk of radon in Silicon Valley homes?

First, though, what is radon?

Per the EPA website, “Radon (chemical symbol Rn) is an odorless, colorless, radioactive gas. It comes from the natural decay of uranium and radium found in nearly all rocks and soils. Radon can move up from the ground into buildings through openings in floors or walls that are in contact with the ground.”

If the idea that a radioactive carcinogenic gas can enter your home or workplace completely unnoticed spooks you, that’s understandable. Thankfully, it is uncommon to find radon at high enough concentrations for concern in Silicon Valley. It’s helpful in that regard that it’s a region with few smokers and few basements, both of which can increase the risk.

That being said, radon can be found all over the world, and similarly, homes high in radon can be found anywhere, though they are more or less common depending on where you are.

So how do you know your radon risk?

Santa Clara County is considered to be a moderate, and not high, radon area. Different geological conditions may make an area more or less prone to high levels of radon gas, though, so even here it is possible to have a radon risk.

The U.S. Environmental Protection Agency (EPA) and the U.S. Geological Survey have mapped by county the average potential radon levels in the area, divided into three zoning (Level 3 being the lowest and Level 1 the highest average measurement zones) for buildings without radon remediation. Santa Clara County is a Zone 2 area per the map linked to above. Check the map at Berkeley Lab Columbia Univeristy Radon Project page. Areas with the greatest risk, and which suggest remediation, are those in Zone 1. The are counties with predicted average indoor radon screening levels greater than 4 pCi/L.

If you would like to check your home’s radon risk levels, there are two tests you can use to measure indoor exposure: a short-term test and a long-term test, and both are affordable. The short-term test only takes a few days, might cost around $15, and is a less reliable way to get results quickly. Long-term measurements take a year and uses detectors placed one on each living level of the house (so approximately $25 for a single-story, $50 for a two-story home). These are much more accurate, so they are the ones preferred by researchers and home owners, but the results will take longer to reach and the cost is higher.

Worst-case-scenario, you have measured 4+ pCi/L (picoCuries per liter of air), the level at which the EPA recommends remediation. Now what? Prepare to spend a few thousand dollars (a great bargain to keep you and your family healthy). The standard treatment involves the installation of a pipeline and fan system which will pull the seeping gas from the ground beneath your house and redirect it outside where it can disperse safely in the air. The only apparent downside to this procedure (other than the time and cost of installation) is that your heat and air conditioning costs may rise slightly. Check with the experts, though, to get the full scope of both the risk and the remediation impact.

Read more at the pages listed below.