However, the main findings were as follows: people using smoky coal had an up to 30-fold higher risk of lung cancer compared with those using smokeless coal and wood (4); lung cancer patients with coal exposure history in Xuanwei had a higher KRAS mutation rate (11, 33) (Table 4); and the occupation of patients (living/working in the rural area, e.g., farmers) was independently associated with an increased rate of EGFR compound mutations in this study. This evidence concerns the gene KRAS and lung cancer.