At JCP, we're frequently contacted by real estate brokers and REALTORS® who are concerned about conflicting information regarding radon issues and appropriate disclosure. It seems that recently, information has been circulating which is based on at least one outdated study of radon exposure, and it, in turn, is causing quite a bit of confusion--and fear--in the industry. JCP wants you to get the real story.
A more recent analysis, funded in part by the U.S. Environmental Protection Agency (EPA), concludes that average radon levels throughout California are well below the EPA-defined guideline for hazardous levels.
The Real Story
All of California's 58 counties have a predicted median annual-average living-area concentration of radon below 2.0 pCi/L (picocuries per liter of indoor air) -- which is well below the EPA's guideline level of 4 pCi/L and within the range of the lowest hazard zone (Zone 3) on the 1993 EPA Map of Radon Zones.
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Information about the potential hazard of radon is included in Chapter VII of the Homeowners Guide to Earthquake Safety and Environmental Hazards booklet. Nevertheless, there is a question as to whether providing this booklet constitutes adequate disclosure.
In fact, we're often asked if the information makes buyers sufficiently aware of this natural hazard. That's why we include a radon advisory in The JCP Report (page 11) that provides the most current information for sellers and buyers.
The Latest Scientific Research
JCP Geologists does not rely on the EPA's 1993 Map of Radon Zones as a basis of our radon advisory. Instead, we report the updated assessment of radon exposure published in 1999 by the Lawrence Berkeley National Laboratory (LBNL) and Columbia University, under support from the EPA, the National Science Foundation, and the US Department of Energy.
Based on this recent assessment, JCP's radon advisory for all properties in California is as follows:
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All of California's 58 counties have a predicted median annual-average living-area concentration of radon below 2.0 pCi/L (picocuries per liter of indoor air) -- which is well below the EPA's guideline level of 4 pCi/L and within the range of the lowest hazard zone (Zone 3) on the 1993 EPA Map of Radon Zones.
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Only 10 counties in the state, all of them rural, have an estimated mean annual radon level above 1.0 pCi/L.
A "median", like an average, is a central value. The "median concentration" means that half of the homes in a county are expected to be below this value and half to be above it. All houses contain some radon, and a very few houses will contain much more than the median concentration. The only way to accurately assess long-term exposure to radon in a specific house is through long-term testing (sampling the indoor air for one year or more).
"Short-term" samples misrepresent "long-term" risks
The 1993 EPA Map of Radon Zones shows "short-term" radon exposure averaged by county. It was based on "screening measurements" that were intentionally designed to sample the worst-case conditions for indoor air in US homes--using spot checks (sampling for just a few days), in the poorest air quality (with sealed doors and windows), at the worst time of the year (winter), in the worst part of the house (the basement, if one was available).
These short-term, winter, basement measurements are both biased and variable compared to long-term radon concentrations (averaged over a year) in the living area of a house. Just as a snap-shot in time can miss the whole picture, short-term measurements can overestimate a hazard if the samples are intentionally biased.
Long-term concentrations--measured in the rooms where people actually live their lives--are a more accurate way to judge the long-term health risk from radon. This was the object of the recent LBNL study, to re-analyze the old EPA data and predict the living-area concentrations of radon averaged over a whole year. The result is a new radon map in which California's population centers are a "cool" blue (instead of the hot colors on the old EPA map).
The authors of the new report certainly acknowledge that very high levels of radon (above 10 or 15 pCi/L) are definitely dangerous, and that lower levels (2 to 10 pCi/L) are probably somewhat dangerous, with higher levels leading to higher risks.
They add that "typical" long-term indoor radon concentrations below 2.0 pCi/L (the range in California) "might cause slightly increased risk compared to no radon at all, but such risk is probably very small...compared to other risks that we tolerate every day (like slipping in the shower, stumbling down the stairs, having a fire at home, etc.)"
Should my home be tested?
Anyone concerned about radon exposure is encouraged to have the home in question tested for radon levels. In fact, the EPA recommends that all homes be tested for radon. Unfortunately, for the reasons outlined above, the EPA expressly disclaims the use of its 1993 map for determining whether any house should be tested for radon, and authorizes no other use of its 1993 map for property-specific purposes.
Is there any help? As an outgrowth of the new study, the "Radon Project" website of Columbia University offers an online webpage to help homeowners determine whether a specific house should be tested for radon or modified for radon reduction.
