Lung cancer among workers exposed to silica dust in Chinese refractory plants

A retrospective cohort mortality study was conducted for lung cancer among silica and clay brick workers at 11 refractory plants in China. The cohort included 6266 male workers employed before 1962 and followed between 1963 and 1985. The standardized rate ratios (SRR) were obtained by comparing the mortality rates of the silica-exposed cohort with those of a population of 11 470 male steel workers. As expected, significant excesses were observed for all deaths, all cancers, lung cancer, cardiorespiratory diseases, pulmonary heart diseases, and pulmonary tuberculosis. The lung cancer SRR was 1.49 (P < 0.01) for the total cohort. The increased lung cancer risk was attributed to the silicotics (SRR 2.10; P < 0.01) in the cohort. Higher lung cancer risk was found with increasing latency and severity of silicosis; this finding suggests that the excess was possibly related to occupational exposure to silica dust. Among the silicotics, there was a twofold excess of lung cancer risk among both the nonsmokers and the smokers.