Risk of chronic non-carcinogenic and internal respiratory exposure to Cu and Zn from particulate matter 2.5 in different microenvironments

This study investigated the respiratory exposure characteristics and health risks of Cu and Zn from particles with aerodynamic diameters smaller than 2.5 mu m (PM2.5) in five microenvironments by using an chronic non-carcinogenic risk index and a physiologically based pharmacokinetic (PBPK) model. The results indicated that taxis and the outdoor environment had the highest Cu concentration and that the outdoor environment had the highest Zn concentration. In offices, buses, taxis, and the outdoor environment, the concentrations of Cu and Zn were higher in winter than in summer. In residential buildings, the concentrations of Cu and Zn were higher in summer than in winter. Acceptable levels of health risk due to respiratory exposure to Cu and Zn from PM2.5 were observed for nonelderly and elderly adults in the five microenvironments. The chronic noncarcinogenic risk index values derived for the nonelderly adults were higher than those derived for the elderly adults in residential buildings, buses, and taxis but lower than those derived for the elderly adults in the outdoor environment. The results of exposure assessment based on the PBPK model indicated that the concentrations of Cu and Zn from PM2.5 were high in the liver and kidney but low in arterial and venous blood. After respiratory exposure was stopped and the pollutant concentrations reached a steady state, the highest concentrations of Cu and Zn were found in muscles. The muscles and brain exhibited the highest internal exposure risk index values for Cu and Zn. According to these results, the simulation of continuous exposure in multiple microenvironments (rather than a single environment) can accurately reflect the exposure concentration and exposure risk index for people in such environments. Hence, during the execution of human exposure risk assessment for various contaminants, internal exposure risk assessment should be preferred over chronic non-carcinogenic risk assessment.