Health surveillance of respiratory disorders among silica-exposed workers in Shanghai in 2014

Objective To assess the prevalence and pattern of respiratory disorders among the silica-exposed workers in Shanghai in 2014. Methods A total of 2 196 workers exposed to silica dust for at least 1 year from 181 factories were studied. The subjects were examined, according to technical specifications for occupational health surveillance in China. The lung function test and chest X-ray were performed. Questionnaires were done to collect the information about demographic characteristic, health behavior,and employment history. Personal sampling was carried out among 619 workers who were sampled by stratified random sampling from 169 factories in the exposure group. Gravimetrical measurement was applied for 8h-TWA concentration of total dust. The contents of free SiO2 in the dust were determined by X-ray diffraction or judged according to the previous reports. Results The geometric mean and gemetric standard error for 8 h-TWA of silica total dust were 1.4 mg/m³ and 3.3 mg/m³, respectively. We found 66.4 percent of the samples were not compliant with national Occupational Exposure Limits(OELs) of silica total dust. The chest X-ray results showed the prevalence of suspected pneumoconiosis or observed subjects was 0.4% among workers exposed to silica dust. The prevalence of FVC loss, FEV₁ loss and FEV₁/FVC loss, and restrictive pulmonary dysfunction were 21.3%, 13.4%, 0.1%, and 19.6%,respectively. The detectable rates of restrictive pulmonary function increased with the duration of silica exposure (χ²trend= 9.214 3,P<0.05). The higher prevalence of restrictive pulmonary dysfunction or chest X-ray was noted in some industries such as general equipment manufacturing, black metal smelting and rolling processing industry, and some processes such as moulding, casting sand, fettler, smelting, foundry, and polishing. Conclusion The concentrations of silica dust in the workplaces were still high. The loss of functional respiratory capacity among these silica-exposed workers need to be concerned, mainly about restrictive pulmonary dysfunction. High-risk industries and processes should be under intensive inspection.