February 16, 2000

Berkeley Lab Science Beat

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BERKELEY, CA — Radioactive radon gas, seeping into houses from the soil below, poses a health risk to humans in certain parts of the United States. Now, a new Web site developed jointly by scientists at the U.S. Department of Energy's Lawrence Berkeley National Laboratory and Columbia University, uses advanced mathematical methods, research on radon gas infiltration, and geologic data, to help homeowners determine when and how to take action to reduce health risk from radon exposure.

The Radon Project Web site was developed by Phil Price of Berkeley Lab's Environmental Energy Technologies Division, along with Andrew Gelman and others at Columbia University’s Department of Statistics.

Radon is a naturally occurring radioactive gas, a product of radioactive decay of radium. Studies of uranium miners have shown that breathing high concentrations of radon can increase the risk of getting lung cancer. Enough radon gas seeps out of soil into basements and crawlspaces in parts of the United States to pose a health risk to people living in homes built on that soil.


"The Radon Project Web site can help homeowners determine whether they are breathing potentially dangerous levels of radon, and whether those risks are high enough to warrant making measurements of their actual exposure, or having a contractor come in right away to install measures to reduce radon infiltration in their house," says Price. "Policymakers can also use the site as a tool to determine optimal policies for addressing radon health risks."

At the Radon Project Web site, users are prompted to choose their home state and county from a U.S. map and then asked a few questions about their basement and radon measurements that have been made in their area. They are also asked how many smokers and non-smokers live in the house since radon exposure increases the risk of lung cancer more for smokers than non-smokers.

Default values for acceptable risk levels and the estimated costs of reducing exposure to acceptable levels are automatically entered. A user can adjust these values if he or she desires. With this information, software calculates the probable level of radon exposure in the user's home then displays an exposure probability curve and a simple table showing the costs of various actions, i.e., doing nothing, short- or long-term testing to measure radon level accurately, or immediate remediation. Recommendations are made based on the exposure level calculated.

Radon levels between 2 and 10 picoCuries per liter (pCi/L) probably pose some risk and levels above 10 pCi/L are considered definitely dangerous by experts in the field. Research suggests that between 50,000 and 100,000 homes in the U.S. have radon concentrations in living spaces in excess of 20 pCi/L. This level is roughly equivalent to the lifetime exposure of a uranium miner and appreciably increases cancer risk. However, radon levels can vary tremendously even within a single county,

To cope with the uncertainty as to how much radon might be present in a specific locale, the Radon Project Web site software employs a unique hierarchical method of modeling.

"Hierarchical modeling allows the software to take the spatial variability of radon into account when calculating the odds of radon exposure where the home is located," says Price.

Price worked with other Berkeley Lab researchers, and with Gelman at Columbia, to predict the radon distribution in almost every U.S. county. Predictions are based on indoor radon data provided by the Environmental Protection Agency, geologic information from the U.S. Geological Survey, and other data.

Gelman and Price, along with Columbia graduate student Chia-yu Lin, then developed a method for using these county predictions along with household information to analyze radon risks and remediation costs for individual homes. Price and Gelman developed their Web site to implement this method.

Berkeley Lab researchers have been studying radon infiltration into U.S. homes for more than 15 years and helped develop the currently preferred remediation method.

A description of the theory used in the Radon Project Web site software was published in the journal Statistical Science, v. 14, no.3, pp 305-337, "Analysis of Local Decisions Using Hierarchical Modeling, Applied to Home Radon Measurement and Remediation," by Chia-yu Lin, Andrew Gelman, Philip Price and David Krantz.

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