Health implications of wintertime fine particulate matter from southwestern China

The health impacts of aerosols from southwestern China remain poorly understood. To identify the key chemical contributors and sources of PM_2.5 toxicity in this region, detailed chemical composition (carbonaceous and inorganic species), different air volume normalized acellular oxidative potential (OP) metrics (OPDTTV and OPEPRV), and cellular oxidative stress (in vitro ROS_V) were measured using PM_2.5 collected from Chongqing. OPDTTV was measured to be 1.1-5.4 nmol min^-1 m^-3 with a mean value of 2.8 nmol min^-1 m^-3, which was higher than the values reported in other coastal cities. In particular, airborne radicals (OPEPRV) were measured to be in the range of 4.1 × 10^-3-2.3 × 10^-2 nmol m^-3 with a mean value of 1.2 × 10^-2 nmol m^-3. The OP_V and in vitro ROS_V increased significantly during haze episodes compared with those during clean episodes. OC, Cu, Zn, polycyclic aromatic hydrocarbons (PAHs), and oxygenated PAHs (OPAHs) were observed to be the major contributors to OPDTTV, while nitrated PAHs (NPAHs), EC, Fe, and Cu primarily influenced OPEPRV and in vitro ROS_V. Backward trajectory and potential source contribution function (PSCF) analysis indicated that the source of PM_2.5 oxidative stress effects was mainly derived from the local and western air masses, indicating the roles of atmospheric aging and industrial emission in the health impacts of PM_2.5. Overall, by revealing that transition metals, PAHs, and functionalized PAHs are the most imperative components for both the acellular and cellular health impacts of wintertime PM_2.5 of southwestern China, this work sheds light on future mitigation strategies for improving urban air quality from a public health perspective.