Natural inhalation exposure to coal smoke and wood smoke induces lung cancer in mice and rats.

In an rural area with a high mortality rate of lung cancer in humans, mice and rats were placed in an environment in which they inhaled coal smoke and wood smoke in indoor air for 15 to 19 months. The incidences of lung cancer in mice in the control group, wood group, and coal group were 17.0% (29/171), 45.8% (81/177), and 89.5% (188/210), respectively: in rats the incidences were 0.9% (1/110), 0 (0/110), and 67.2% (84/125), respectively. In addition, the pollutants in the air were analyzed. The results indicate that coal smoke is a highly significant risk factor for lung cancer in humans in Xuan Wei County of Yun Nan Province in China.