Every year, lung cancer accounts for more deaths in the United States than any other form of cancer. Based on estimates released by the American Cancer Society, more than 160,000 Americans die from lung cancer each year.
Although smoking is the primary cause, it is not the only one. A number of occupational and environmental carcinogens increase lung cancer risk. The most well known risk factors include radon and asbestos; other types of exposure include bis-chloromethyl ether, arsenic, formaldehyde, chromium, nickel, ionizing radiation, hard metal dust, polycyclic aromatic hydrocarbons, and vinyl chloride. Several of these factors work synergistically with tobacco smoke leading up to lung cancer, and some of these also act as independent risk factors amongst nonsmokers. For instance, in a Chilean study focusing on cancer mortality between 1950 and 1997, it was noted that the mortality risk ratio of lung cancer was 3 to 4 in a specific region where the drinking water had a high percentage of inorganic arsenic. This conclusion could not be explained on the basis of tobacco use patterns. The potential link between exposure to arsenic and lung cancer is further substantiated by a Taiwanese study which noted a progressive reduction in mortality rate of lung cancer when arsenic was eliminated from the water supply of a community.
Public health experts have been concerned about the risk of lung cancer among the general population due to radon exposure. A gaseous decay product of radium-226 and uranium-238, radon can damage respiratory epithelium through the emission of alpha particles. Uranium miners, working in underground mines, who face occupational exposure to radon and also to its decay products, have an increased lung cancer risk. Also, an interactive effect between cigarette smoking and exposure to radon has been noted.
Radon is found in soil, groundwater and rock, and it has shown to accumulate in homes. However, in face of conflicting data, the risk associated with radon exposure remains unclear. A meta-analysis conducted in 2005 that covered 13 European case- control studies demonstrated that a linear relationship existed between the amount of radon found in the home and lung cancer risk. Although small, the increased risk was significant statistically, and it was estimated by the authors that around 2 percent of deaths in Europe may be due to exposure to radon.
Wood smoke exposure is also a cause. In many areas of the world, wood is burned either for heating or cooking. A number of studies have demonstrated that exposure to smoke from burning of wood is linked with an increased lung cancer risk.
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