The effect of subcontractor status on occupational injury and disease incidence: a cross-sectional study using the 9th Occupational Safety and Health Company Survey.

BACKGROUND: Despite the efforts of contractors to identify and reduce any occupational risk that exists in subcontracted works, if the associated risks cannot be eliminated and reduced and subcontractors have to take risks, this situation can be called 'risk transfer.' The hypothesis of this study is that the contractor-subcontractor status of a company affects the risk of occupational injury or occupational disease. The inside subcontractor and outside subcontractor represent subcontractors located inside and outside the contractor workplace, respectively. METHODS: The dataset from the 9th Occupational Safety and Health Company Survey (OSHCS) with 5219 workplaces, which was conducted in South Korea, was used. After the exclusion of 45 workplaces with no reported employees, 5174 workplaces with a total of 1,072,583 employees were used for analysis. Poisson regression was applied with the contractor-subcontractor category as the independent variable and the number of both occupational injury and disease cases per workplace as the dependent variable. Poisson regression is an appropriate model for the count-data analysis of rare events that do not follow a normal distribution but rather follow a right-skewed distribution. RESULTS: Compared to the 'contractor' category, the 'outside contractor' reported the highest risk ratio, 1.66 (95% Confidence Interval, CI 1.09-2.41). The 'inside contractor' reported the second highest risk ratio, 1.39 (95% CI 1.07-1.78). In contrast, the 'both contractor and subcontractor' category reported a statistically significant decreased risk ratio of 0.69 (95% CI 0.57-0.84). The 'neither contractor nor subcontractor' category showed a statistically equivocal risk ratio of 0.91 (95% CI 0.76-1.07). CONCLUSION: This study confirmed the increased risk of occupational injuries and diseases for subcontractors, whether located inside or outside the contractor workplace (1.66-fold and 1.39-fold increased risk, respectively). Future individual-based epidemiologic studies such as case-control and cohort studies could provide more detailed information such as specific risk factors associated with subcontracted works and confounders according to industry classification.