Occupational epidemiological studies conducted in workers with silicosis have consistently shown increased risks of lung cancer and chronic obstructive pulmonary diseases (COPD) [1–3]; these increased risks, however, could be linked to their smoking behaviors because silicotic workers were generally more prone to cigarette smoking than the referent population. Yet, in the previous historical occupational cohort studies involving standardized mortality ratio (SMR), cigarette smoking was simply skeptics as a potential confounder to be adjusted or it was even not adjusted at all. Apart from being a possible confounder, smoking may interact with silica dust or the associated silicosis to modify the risk of multiple disease outcomes, in particular the diseases to the lungs, as the lungs are the target organs of hazardous substances (including cigarette smoke) whose route of entry of the body is by
inhalation. Long-term cigarette smoking may damage the respiratory system [4], leading the smokers to being more susceptible than the never smokers to the adverse health effects due to the prolonged exposure to hazardous silica dust or the associated silicosis. It remains unclear whether the joint effect of smoking and silicosis differs amongst a variety of diseases to the lungs; this study aims to address this knowledge gap by using data from a historical cohort of Chinese workers with silicosis.