What about Radon? (in Shasta, Tehama, Butte counties)

As a home inspector working within the Redding-Chico area focused on Shasta, Tehama, and Butte counties in California, I have not witnessed high concerns about testing for radon gas during home transactions. This is likely justified, because most of the valley floor in our area between the Northern Coast, Cascade, and Sierra-Nevada ranges is located within EPA’s Zone 3, which is the lowest, safest range for anticipated radon exposure.

However, what Zone 3 (yellow) represents is the statistical probability that a test for radon gas in that area will result in less than 2 pCi/L (picocuries per liter) based upon collected data. It does not mean that your house does not have higher levels of radon gas, just that that an elevated test result is less likely to happen versus other parts of the county. Zone 2 (orange) has the probability that a radon test will be between 2 pCi/L and 4 pCi/L. And, Zone 3 (red) has the probability that a test will be over 4 pCi/L.

Before we get too far, let us review what is radon gas and how the EPA came up with the Radon Zone map. Radon is a colorless, odorless, tasteless, and chemically-inert gas that is formed by the natural radioactive decay of uranium in rock, soil, and water. It naturally exists in low levels widely across the Earth’s crust and can be found in all 50 states. Once produced in the ground, it moves through the soil to the air above or dissolves into the groundwater. Of the two, inhaled airborne particles are much more hazardous to humans. The EPA has determined that ANY amount of long-term exposure to radon gas increases your risk of contracting lung cancer.
 
So, is 2 pCi/L safe? The technical answer is “no” as long-term exposure to radon is a hazard in any amount. However, there is one important caveat. Radon gas can be found anywhere and everywhere. So, if you were to take a long walk around the country, the EPA has determined your average exposure to radon would be about 4 pCi/L. Thus, that is why the EPA came to use 4 pCi/L as its standard. If your house has radon gas in higher concentration that 4 pCi/L, then your family is at higher risk of contracting lung cancer versus the natural environment and the EPA recommends you take measures to mediate that additional risk.
 
The EPA Radon Zone maps were derived from aggregated test results based upon ZIP code data. The most current ZIP code based radon data for all counties within California can be found at the following website.
 
https://www.city-data.com/radon-zones/California/California.html
 
Although based upon a limited sample set, you will notice that certain ZIP codes within Shasta County (notably 96003, 96007, 96049, and 96069) have had test results reporting greater than 4 pCi/L. The same is true for 96080 (south Red Bluff) in Tehama County plus 95928 and 95969 (Paradise) in Butte County. The EPA recommends that all homeowners test for radon, particularly when purchasing a new home. The results in those ZIP codes, so far, indicate that that caution has been warranted.
 
We recommend that all new homeowners test for radon, starting with the DIY home tests—see link below. Because the DIY tests are not 100% accurate, with both false negatives and positives possible, we recommend that you purchase and perform two separate tests. Follow the instructions carefully to get the best results. A typical DIY test kit includes the laboratory processing fee and can be purchased for around $25 each. The following is a product review site for some of the most popular kits:
 
https://bestreviews.com/home/safety/best-radon-test-kits#radon-test-kit-prices
 
Should your test results come back indicating higher than 4 pCi/L, we recommend that you then consult with a radon mitigation specialist. Another aspect concerning radon gas is that it requires an avenue to enter your home, which is where your mitigation specialist will focus and your home inspection report can help. Houses built on raised foundations (crawlspaces) without vapor barriers installed have little to no means of preventing radon gas from the soil from filtering upwards into the house. Radon gas can enter through gaps around piping and electrical connections, as well as cracks in the foundation. Helping to mitigate radon inside a home can be as simple as filling in cracks, sealing around pipes and electrical conduits, installing a vapor barrier, or adding vents to a crawlspace. Additional mitigation could include installing a powered vent into the crawlspace, basement, or even under a concrete slab. Our recommendation would be to also install a radon monitor device inside the home for on-going post-mitigation monitoring (typically less than $100 material cost). All of these measures are relatively modest in cost, as well as have other benefits such as reducing moisture entering the home and are in the range of other types of home repairs.
 
In summary, radon gas, a known carcinogen, is present in Northern CA and a low percentage of homes in our area have seen concentrations exceeding 4 pCi/L that would call for some type of mitigation. The DIY tests are relatively inexpensive, and every homeowner should test their home. Should the test results come back with radon level greater than 4 pCi/L (not very likely, but possible), some moderate costs could be involved to help reduce the radon gas that enters the home to below 4 pCi/L that is the average atmosphere background level in the USA, or lower.