JMIR Publications

ABSTRACT

Background:

Despite the increasing awareness of silicosis induced by silica dust, occupational silica exposure remained contributing to a huge disease burden in China. However, recent silica dust exposure levels and silicosis risk in Chinese non-coal mines are still unclear.

Objective:

We aimed to determine the recent silica dust exposure levels, and assess the risk of silicosis in Chinese non-coal mines.

Methods:

As of December 2020, three non-coal mines and one public hospital for occupational health examination were selected to evaluate cumulative hazard ratio (H) and cumulative incidence (I) functions. Meanwhile, we conducted a cross-sectional survey, collecting the prevalence of silica dust exposure (PDE), free silica content, total and respirable dust concentrations (mg/m3), based on 155 non-coal mines. Qualitative risk of silicosis was assessed with International Mining and Metals Commission's risk rating table and occupational hazard risk index, and cumulative hazard ratio (H) and cumulative incidence (I) functions were used in quantitative risk assessment.

Results:

Results of Kaplan-Meier analyses showed that there were significant differences in survival between gender (χ2=7.52, P=.01), and quantitative risk functions were evaluated by using multivariable Cox regression analyses. A total 126 non-coal mines were included in cross-sectional survey, and median of PDE, total dust, total silica, repirable dust, respirable silica were 61.6%, 1.30 mg/m3, 0.39 mg/m3, 0.58 mg/m3, 0.15 mg/m3, respectively. Nonmetal and nonferrous metal, especially small and open-pit non-coal miners suffered high silica dust exposure levels. Overall, non-coal miners had medium risk of silicosis. The risk of silicosis caused by total dust exposure was high, and with 10, 20 and 30 years’ exposure, cumulative incidences would be 6.8%, 25.1% and 49.9%, respectively. As for respirable dust exposure, risks were medium regardless of mine category, production scale or mining method, and with 10, 20 and 30 years’ exposure, cumulative incidences would be 6.8%, 27.7% and 57.4% , respectively. In addition, nonmetal and nonferrous metal, especially small and open-pit non-coal mines had higher risks and cumulative incidence.

Conclusions:

Chinese non-coal miners may still suffer high-level silica dust exposure and medium-level silicosis risk, especially in nonmetal, nonferrous metal, small and open-pit mines.