Employment Status and Lung Function Among Coal-Powered Electrical Plant Workers: A 5-Year Follow-up Study.

BACKGROUND: Coal-powered electrical plant workers are exposed to coal dust in the entire work process. In South Korea, the processes with relatively high exposure to hazardous substances are mainly conducted by subcontractor employees. The harmful substances may cause pneumoconiosis, lung cancer, as well as a decrease in lung function. However, few studies have investigated changes in lung function among plant workers. The current study hypothesizes that the lung function of workers would be reduced by dust exposure and these reductions differ by employment status. METHODS: This study was conducted on 1,108 workers in coal-powered electrical plants who underwent lung function tests as a special health check-up from 2013 to 2018. The study population was divided into three groups according to the work they mainly perform. These groups were the contractor operator, subcontractor operator, and subcontractor maintenance worker. To compare the exposure level to hazardous substances, the exposure index was calculated with using the measurement data for the workplace environment. To confirm the change of lung function, this study used the repeated-measure analysis of variance. RESULTS: The subcontractor and the contractor had the highest and lowest exposure indices at 4.5 and 1.7, respectively. The lung function indicators significantly decreased among the subcontractor maintenance and operating workers compared with the contractor workers after 5 years. The pulmonary function with forced vital capacity (in liters) in subcontractors 1 and 2 decreased by 0.1 and 0.2 L, respectively. Forced expiratory volume in 1 second (in liters) also decreased in the subcontractors. In addition, the decrease in pulmonary function level over time differed according to each group because the interaction between time and employment status was statistically significant (P < 0.01). CONCLUSION: These results suggest an association between coal dust and lung function deterioration. Also, differences in exposure can cause disparities in health outcomes even for workers in the same workplace.