Safe from Radon Gas? Statistically speaking the majority of homes will not have significant levels of radon to be considered health risks, but that still leaves tens of thousands of homes in San Mateo County that could be considered unhealthy or outright dangerous.

What is Radon Gas?

According to the CDC Radon is an odorless, invisible, radioactive gas naturally released from rocks, soil, and water which comes from decaying Uranium. Radon can get into homes and buildings through small cracks or holes and build up in the air. Over time, breathing in high levels of radon can cause lung cancer. According to the EPA, only smoking causes more lung cancer deaths than radon gas exposure. EPA Report

Where is Radon Found?

Are you safe from radon gas?

Most of us were informed that Radon is primarily an East Coast issue and not a problem in California, but recent data is starting to suggest otherwise. The California Department of Public Health has published a Radon exposure table by zip code: CDPH Report. Even if your zip code does not show high incidents of radon gas, you should still test because sometimes radon gas shows up quite randomly.

So, are you safe from Radon Gas? Based on indoor-radon survey results, the radon potential zone map developed by the Department of Conservation and 2010 U.S. Census data, an estimated 34,853 people in San Mateo County live in residences with indoor-air radon concentrations likely at or exceeding 4.0 pCi/L.

An estimated 9,222 people live in homes that will likely test at 10 pCi/L or more, and about 4,050 people are estimated to live in homes that will likely test at 20 pCi/L or higher. Recall that anything over 4.0 pCi/L is considered unsafe. So that’s approximately 50,000 people potentially living in homes in San Mateo County with Radon levels exceeding safe levels. Doesn’t sound like we are safe from Radon gas?

Of the 88 sites tested in San Carlos CA in the CALIFORNIA GEOLOGICA L SURVEY by the Department of Conservation, 5 tested at or above 4.0 pCi/L . So, while only 5.7% of homes/buildings tested beyond safe levels, that is still significant when considering there are 11,393 households in San Carlos. Let’s assume some of these are multi-level buildings without danger of exposure and that only 8,000 homes in San Carlos could be potentially exposed to Radon. Then 5.7% is still about 450 homes that could have high levels of Radon in San Carlos or roughly 1,230 people. That’s significant and worth testing.

Menlo Park, Atherton and La Honda had 30%+ of sites testing at or above 4.0 pCi/L. Redwood City had 23% of test sites test above 4.0 pCi/L but it also had some of the highest levels of radon gas in all of California. So, if you have friends in those cities, you might give them a heads up.

Full report containing all this data.

So, are you Safe from Radon Gas?

You can only know whether you are safe from Radon gas by testing your home. However, don’t panic. In the East Coast and in many Mid-West states lots of people live in homes on land with lots of Radon and they are perfectly safe. The key is to remediate the problem if one exists. Remediation means installing ventilation in the home if radon levels are at 4 pCi/L or more.

What To Do?Radon gas test kit

To be safe from Radon Gas, test your home! You can buy test kits online or at Home Depot and test it yourself, but I recommend using a professional. For an excellent person to test your home for radon, visit Having a professional test your home should cost approximately $400, which is well worth it considering what’s at stake!

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