A case-crossover study on 75-cases occupational injuries at nonferrous mines

Objective To explore risk factors of occupational injuries and the intensity of these factors at nonferrous mines. Methods The case-crossover design was used to study 75 injured workers among a nonferrous mine in 2006. The information of their exposure factors was collected respectively 10 minutes before the injury, and the same period in previous working day and last week was analyzed by matched-time interval approach and general frequency analysis to evaluate risk degree of every instantaneous exposure factors. Results Matched-time interval analysis showed the odds ratios of 11 risk factors were more than 1, including work conditions, labor management and individual behavior, among other thmgs. In general frequency analysis, the relative risks of all risk factors were more than 1, except unsafe wearing and without protective equipment. The analysis results of two methods compared, 95% confidence intervals was much narrower in general frequency analysis. Conclusions The occurrence of occupational injuries could be related to many risk factors at nonferrous mines. Case-crossover design can identify the risk factors of occupational injuries and its intensity.