Organic carbon and acidic ions in PM contributed to particle bioreactivity in Chinese megacities during haze episodes.

Fine particulate matter (PM) has been linked to cardiopulmonary disease and systemic effects in humans. However, few studies have investigated the particle bioreactivity in Chinese megacities during haze episodes. The objective of this study was to determine the contributions of chemical components in PM to particle bioreactivity in Chinese megacities during haze episodes. PM samples were collected in 14 megacities across China from 23 December 2013 to 16 January 2014. Average PM concentrations ranged 88.92~199.67 μg/m. Organic carbon (OC), elemental carbon (EC), anions, and cations per unit of PM were linked to cellular bioreactivity (i.e., reactive oxygen species (ROS) as assessed by dichlorodihydrofluorescein diacetate (DCFH) and inflammation as assessed by interleukin (IL)-6 in A549 cells). The contributions of chemicals in PM to ROS and inflammation were examined by the Pearson correlation coefficient and random forests. These results indicated that OC, Ca, SO, Cl, F, K, and NO contributed to ROS production, whereas OC, Cl, EC, K, F, Na, and Ca contributed to inflammation. In conclusion, PM-contained OC and acidic ions are important in regulation of oxidative stress and inflammation during haze episodes. Our findings suggest that severe haze PM events cause deterioration in air quality and may adversely affect human health.