Figure 1. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) of lung cancer in relation to smoky coal sources compared with controls (smokeless coal and wood combined).

All models were adjusted for age, sex, literacy, lung cancer in first-degree relatives, hours spent at home per day, lung disease history, coal-mining work history, smoking, and passive smoke exposure history. Coal types are named after the districts at Xuanwei where they are mined.