A Harvard study suggests the EPA numbers for radon-related deaths may be erroneously high. This information comes after other studies indicate diesel emissions likely played a significant role in the deaths of studied miners that were exposed to elevated levels of radon.
“The U.S. EPA’s estimate of 21,100 lung cancer deaths per year attributable to radon exposure in homes might be overestimated due to neglect [of] the concurrent diesel exposure in miner studies upon which their risk estimates rely,” according the researchers. This study’s data suggests a decrease of 9 to 26 percent in radon deaths, although the researchers say more research is needed to make a definitive conclusion.
“The reduction may be as high as 40% when considering the updated mortality data. This is significant because although this maintains radon’s high public health importance as the second leading cause of lung cancer deaths in the U.S., it is becoming closer to secondhand smoking, which was ranked third (approximately 7,330 lung cancer deaths per year).”
It’s worth noting again that elevated radon exposure is still a significant contributor to lung cancer and lung cancer deaths.
If you’ve ever wondered how the radon level thresholds were developed, here’s a quick summary from the above study (with links!):
“Turner et al.  studied the radon risks based on the American Cancer Society Cohort Prevention study from 1982 to 1988. They observed a 0.15 (95% CI: 0.01, 0.31) increase in the risk of lung cancer death per 100 Bq/m3 (2.7 pCi/L) increase in radon. Darby et al.  reported a collaborative study of 13 European studies indoors, including 7,148 cases of lung cancer and 14,208 controls. They found a significant linear dose-response relation at residential exposure. The relative risk of lung cancer increased by 0.16 (95% CI: 0.05, 0.31) per 100 Bq/m3 increase in radon exposure concentration, quite consistent to the results of Turner et al. . The relation was linear with no threshold observed for radon concentrations below 200 Bq/m3 (5.4 pCi/L). A Germany pooled study  showed a meaningful radon risk at a level of 140 Bq/m3 (3.8 pCi/L), close to EPA’s current action level. Krewski et al. [10, 11] performed combined analysis of seven primary North American case-control studies with a total of 3,662 cases and 4,966 controls. They reported an odds ratio (OR) of 1.10 (95% CI: 1.00, 1.28) after exposure to radon at a concentration of 100 Bq/m3 within the exposure time window 5–30 years prior to the index date. It was compatible with the estimates of 1.12 (95% CI: 1.02, 1.25) per 100 Bq/m3 downwardly extrapolated from the miner data. Collectively, these residential studies have provided robust evidences of association between residential radon exposure and lung cancer risk.”