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Pooling combines the raw data from each study, while meta-analyses combines (often weighted) summary results. The Pooled European and North American Studies found an increased lung cancer risk with prolonged exposure even below the EPA's action level. A global pooling of radon studies is underway right now as well that combines these two data sources. The 4 pCi/L level is not a health based standard like the groundwater standards, If it were a health based standard, the standard (applied like other environmental standards) would be closer to 0.4 pCi/L.

Gary, Pooling is quite different than meta analyses. Gary, the North American Pooling pdfs are quite large, feel free to email me directly and I would be happy to send them as attachments. The European Pooling can be found here - http://www.bmj.com/cgi/content/full/330/7485/223 others, please identify yourself to eliminate needless concerns and unwarranted egregious attacks. just the facts!

Kurt, Good question - Yes, residential radon studies have been funded by governments all over the world and performed in: New Jersey, Missouri I, Canada, Iowa, Missouri II, Connecticut, Utah, S. Idaho Shenyang, China, Stockholm, Sweden, Swedish nationwide, Winnipeg, Canada, S. Finland, Finnish nationwide, SW England, W. Germany, Sweden, Czech Republic, Italy-Trento, Spain, Austria, France, China - Gansu Province, E. Germany, and Russia. The bottom line is that the pooled analyses indicate that prolonged residential radon exposure represents a lung cancer risk at prolonged exposures even under the EPA's action level. Dr. Bill Field

EPA has a fairly updated guide to mold - http://www.epa.gov/mold/ and a nice resource page. One of the benefits of a radon mitigation system is that in many cases it reduces moisture in the basement so in some instances has a secondary benefit. It also helps, in some cases, to prevent soil gases from entering the home.

An excellent book that traces some of the origins of the radon action level is called Radon's Deadly Daughters by Edelstein Michael R. You can probably purchase a used copy from Amazon or some other book outlet for under $10.00. The technical support document for the U.S. EPA Citizen's Guide also provides insights into the action level. "Technical Support Document for the 1992 Citizen's Guide to Radon" (1992), EPA no. 400-R-92-001. Other EPA radon-related publications can be found here -http://www.epa.gov/radon/pubs/index.html Home inspectors can receive free copies of the Citizen Guide and many other publications upon request. These may serve as useful reference materials that can be handed out during a home inspection. Bill Field

Kurt, Interesting comments, working level months were used in the Iowa Radon Lung Cancer Study since cumulative exposure was ascertained. If toxicological thresholds were used, the threshold would be well below 4 pCi/L based on risk. The action level is NOT a risk based guideline. On the other hand, standards can be promulgated for waterborne radon. As you likely know, the proposed waterborne standard is 300 pCi/L based primarily on the off-gassing of radon from water and its resulting risk. It is ESTIMATED that for a typical household, if the waterborne radon is 10,000 pCi/L it will contribute 1 pCi/L to the indoor air. As you can see, the 300 pCi/L will contribute little radon to the indoor air, but nonetheless is risk-based unlike the action level for indoor air. The EPA can not adopt "standards" for indoor air, but only provide guidelines. Bill Field

There have been numerous residential radon studies that clearly demonstrate that prolonged exposure to residential radon even below the EPA's action level of 4 pCi/L significantly increases lung cancer risk. The Iowa Radon Lung Cancer Study as well as the European and North American Pooling Studies support this view. In addition, the risk noted in the studies are in agreement with projections from 40 years of work studying radon-exposed underground miners. See also: http://www.aarst.org/radon_articles.shtml