RESEARCH COMMUNICATION Residential Radon and Lung Cancer Risk: An Updated Meta- analysis of Case-control Studies

Lung cancer was the most commonly diagnosed cancer as well as the leading cause of cancer death globally. It accounts for 13% (1.6 million) of the total cancer cases and 18% (1.4 million) of the cancer deaths in 2008 (Jemal et al., 2011). Although the majority of lung cancer cases can be attributed to active cigarette smoking, radon exposure was also an important contributor to the total burden of lung cancer. In USA, it suggested that 10-15% of the total lung cancer deaths could be attributed to residential radon exposure, making radon the second leading cause of lung cancer death after smoke (NRC 1999). In 1988, the International Agency for Research on Cancer (IARC1998) determined that radon was a cause of human lung cancer. Radon gas is formed during the decay series of uranium-238, a naturally occurring radioactive mineral found in rocks and soils. The fist line of evidence of radon and lung cancer came from occupational studies on miners, especially uranium miners, exposed to high levels of radon (Radford et al., 1984; Howe et al., 1986). Using various modeling approaches, results of lung cancer risk in miners were used to project lung cancer risk for general population exposed to residential radon. However, such direct extrapolation from these studies is uncertain