I recently participated in a course on the risks of radon and thought I’d share some of the wisdom gleaned.  Radon is a naturally occurring gas, and we live amongst it in the normal course of life.  It comes from rocks deep in the soil and is undetectable to our senses but can be tested for with special equipment.  Radon is a carcinogen and is known to cause lung cancer.  Unsurprisingly, smokers are at higher risk of lung cancer with radon exposure.  Radon tests are not required, but if you’ve had one done, you’ll need to disclose that in a real estate transaction. 


Radon is not regulated, but the EPA offers guidance suggesting “safe” levels at or below 4 picocuries per litre or pCi/L.  This target was developed based on the “as low as reasonably possible” rule of thumb in Washington.  For comparison, the strictest guidelines come from the WHO and Germany which set it at 2.7 pCi/L.  Otherwise, the U.S. standard is over 25% more aggressive than the next most aggressive countries.  The difficulty is, there is no “safe” level, any amount of radon can be dangerous.  Don’t panic though, exposure to high levels of radon doesn’t always lead to adverse effects, and, there are ways to mitigate it. 


Location is a key factor, as radon concentrations vary geographically.  I’ve included a heat map from the EPA for reference.  Levels fluctuate with time, which makes a long-term (1 year) test ideal.  Levels vary with wind, rain, barometric pressure, window opening and much more.  Although 75% of rooms in the home don’t fluctuate, it is the 25% that is the doozy.  You should probably test at least two rooms, especially if you have a larger or more complicated home.  A two-day test is sufficient 94% of the time, according to the EPA, but the best accuracy remains a long-term test.  Still many professionals recommend the short-term test, because if you’ve got high numbers you’ll want to mitigate asap. 


Make sure you use a certified tester or mitigator.  There are plenty of quacks out there who don’t know what they’re doing but are happy to take your money.  There are two certifying agencies in the U.S., the American Association of Radon Scientists and Technologists or the National Radon Safety Board.  A professional test costs approximately $150-200 for the first location, and $50-100 for each additional.  (Location refers to test site, which could, for example, be a room in the house.  It does not mean the whole house).  Alternatively, for the DIY crowd, you can purchase an at-home test kit online or at companies like Lowe’s or Home Depot, which cost around $25.  They work well, however, they are only as good as the user… you must carefully follow the instructions and do your part correctly, or the results will be flawed. 


For the new home builders, you cannot effectively test the soil before you build.  Instead, for those in areas that have higher radon concentrations, a preventative system should be (or may be legally mandated as it is in the city of Santa Fe) installed during the building process.  As an economist, this makes sense to me for another reason – the cost to mitigate can be many times (try 7x) higher than the cost of a preventative system. 


In conclusion, if you live in a red zone, you may want to test for it.  If it were me, I’d start with a cheap, at-home DIY test.  If your concentrations are high, you can reach out to a local expert and let them take it from there. 



Posted by Elle Seybold on


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