Indoor radon exposure and excess of lung cancer mortality: the case of Mexico-an ecological study

Radon is a radioactive gas that can migrate from soils and rocks and accumulate in indoor areas such as dwellings and buildings. Many studies have shown a strong association between the exposure to radon, and its decay products, and lung cancer (LC), particularly in miners. In Mexico, according to published surveys, there is evidence of radon exposure in large groups of the population, nevertheless, only few attention has been paid to its association as a risk factor for LC. The aim of this ecological study is to evaluate the excess risk of lung cancer mortality in Mexico due to indoor radon exposure. Mean radon levels per state of the Country were obtained from different publications and lung cancer mortality was obtained from the National Institute of Statistics, Geography and Informatics for the period 2001-2013. A modelproposed by the International Commission on Radiological Protectionto estimate the annual excess risk of LC mortality (per 10(5)inhabitants) per dose unit of radon was used. The average indoor radon concentrations found rank from 51 to 1863 Bq m(-3), the higher average dose exposure found was 3.13 mSv year(-1)in the north of the country (Chihuahua) and the mortality excess of LC cases found in the country was 10 +/- 1.5 (range 1-235 deaths) per 10(5)inhabitants. The highest values were found mainly in the Northern part of the country, where numerous uranium deposits are found, followed by Mexico City, the most crowded and most air polluted area in the country. A positive correlation (r = 0.98p < 0.0001) was found between the excess of LC cases and the dose of radon exposure. Although the excess risk of LC mortality associated with indoor radon found in this study was relatively low, further studies are needed in order to accurately establish its magnitude in the country.