Radon gas health hazard by Ray Sahelian, M.D.
February 10 2016

Radon is a radioactive gas. It comes from the natural decay of uranium that is found in nearly all soils. It typically moves up through the ground to the air above and into your home through cracks and other holes in the foundation. Your home traps radon inside, where it can build up. Any home may have a radon problem. This means new and old homes, well-sealed and drafty homes, and homes with or without basements.
   Radon is natural radioactive noble gas that can be found in soil, water, outdoor and indoor air. Exposure to radon accounts for more that 50% of the annual effective dose of natural radioactivity. Low levels of radon can be found in drinking water; however, radon released during water usage adds small quantities to indoor radon concentration.

Radon in the House
Radon is formed from the natural radioactive decay of radium and uranium found in the soil beneath the house. The amount of radon in the soil depends on complex soil chemistry, that varies from one house to the next. Radon levels in the soil range from a few hundred to several thousands of pCi/L. The amount of radon that escapes from the soil to enter the house depends on the weather, soil porosity, soil moisture, and the suction within the house. There appears to be an association between residential radon exposure and lung cancer risk.

Radon Exposure
Gene variants that result in decreased amounts of glutathione-S-transferase M1 (GSTM1), may raise the risk of lung cancer related to radon exposure. The findings confirm that such variants also seem to increase the cancer-causing effect of secondhand smoke. Both radon and secondhand smoke are thought to promote carcinogenesis through the formation of reactive oxygen species. GSTM1 is an enzyme that detoxifies these species and their derivatives.

Radon, cancer, and Lung Cancer
There appears to be an association between residential radon exposure and lung disease. Radon is an established human lung carcinogen based on human epidemiological data supported by experimental evidence of mutagenesis studies in cell culture and laboratory animals. Extrapolation from studies on miners suggested that radon is the second leading cause of lung cancer death after tobacco smoke. The majority of studies on the relationship between radon and other types of cancers showed weak or no association. Studies show that the risk of stomach cancer and other gastrointestinal malignancies from radon in drinking water is small. Studies of the genetic and cytogenetic effects of indoor radon yielded equivocal results; while radon exposure in miners induces gene mutations and chromosomal aberrations. Numerous in vitro cytogenetic studies demonstrated that radon induces different types of genetic and cytogenetic damage that is likely to play a role in radon lung carcinogenesis.

Indoor radon exposure and lung cancer risk. Results of an epidemiological study carried out in France
Rev Mal Respir. 2005. Institut de Radioprotection et de Surete Nucleaire, Laboratoire d'Epidemiologie, Fontenay-aux-Roses, France.
Several epidemiological studies have indicated an increased risk of lung cancer associated with indoor radon exposure. As part of a large European project, a hospital based case-control study was carried out in four regions of France: Auvergne, Brittany, Languedoc-Roussillon and Limousin.  Individual data on demographic characteristics, residential history, smoking and occupational exposures were collected during face-to-face interviews. Radon concentrations were measured in each dwelling occupied by the subject during the 30-year period prior to the interview. 486 cases and 984 controls were included in the study. After adjustment for age, sex, region, smoking history and occupational exposure, the risk of lung cancer increased by 4% per 100 Bq/m(3), when considering cumulative exposure in the 30 years prior to diagnosis. The study indicates a positive association between lung cancer risk and indoor radon exposure. The risk estimate per unit of radon exposure is in agreement with other recently published indoor case-control studies.

An overview of the North American residential radon and lung cancer case-control studies.
J Toxicol Environ Health A. 2006.Department of Occupational and Environmental Health, Department of Epidemiology, College of Public Health, University of Iowa, Iowa City, Iowa
Extrapolations from epidemiologic studies of radon -exposed miners project that approximately 18,000 lung cancer deaths per year in the United States alone are attributable to residential radon progeny exposure. Because of differences between the mines and the home environment, as well as differences (such as breathing rates) between miners and the general public, there was a need to directly evaluate effects of radon in homes. Seven major residential case-control radon studies have been conducted in North America to directly examine the association between prolonged radon progeny (radon) exposure and lung cancer. Six of the studies were performed in the United States including studies in New Jersey, Missouri (two studies), Iowa, and the combined states study (Connecticut, Utah, and southern Idaho). The seventh study was performed in Winnipeg, Manitoba, Canada. The goal of this review is to provide additional details regarding the methodologies and findings for the individual studies. Radon concentration units presented in this review adhere to the types (pCi/L or Bq/m3) presented in the individual studies. One picocurie per liter is equivalent to 37 Bq/m3. Because the Iowa study calculated actual measures of exposure (concentration x time), its exposures estimates are presented in the form WLM(5-19) (Field et al., 2000a). WLM(5-19) represents the working level months for exposures that occurred 5-19 yr prior to diagnosis for cases or time of interview for control. Eleven WLM(5-19) is approximately equivalent to an average residential radon exposure of 4 pCi/L for 15 yr, assuming a 70% home occupancy.

2009 New studies have found direct evidence of a lung cancer risk from the radon gas in many homes. Officials on the U.N. Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) said the finding provided the first quantifiable evidence of the risk in homes from radon, long seen as a potential health risk. The World Health Organization (WHO) and other agencies were revising recommendations on maximum levels of radon in homes and workplaces based on the 20 studies involving tens of thousands of lung cancer patients in North America, Europe and China.

J Korean Med Sci. 2015. Risks of Lung Cancer due to Radon Exposure among the Regions of Korea. Radon is likely the second most common cause of lung cancer after smoking.

Esophageal cancer potential
Int J Radiat Biol. 2014. Residential radon exposure and esophageal cancer. An ecological study from an area with high indoor radon concentration (Galicia, Spain).