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Although air quality guidelines generally use the atmospheric concentration of fine particulate matter (PM 2.5) as a metric for air pollution evaluation and management, the fact cannot be ignored that different particle toxicities are unequal and significantly related to their sources and chemical compositions. Therefore, judging the most harmful source and identifying the toxic component would be helpful for optimizing air quality standards and prioritizing targeted PM 2.5 control strategies to protect public health more effectively. Since the combustions of fuels, including oil, coal, and biomass, are the main anthropogenic sources of environmental PM 2.5 , their discrepant contributions to health risks of mixed ambient aerosol pollution dominated by the respective emission intensity and unequal toxicity of chemical components need to be identified. In order to quantify the differences between these combustion primary emissions, 10 types of PM 2.5 from each typical source group, i.e., vehicle exhaust, coal combustion, and plant biomass (domestic biofuel) burning, were collected for comparative study with toxicological mechanisms. In total, 30 types of individual combustion samples were intercompared with representative urban ambient air PM 2.5 samples, whose chemical characteristics and biological effects were investigated by component analysis (carbon, metals, soluble ions) and in vitro toxicity assays (cell viability, oxidative stress, inflammatory response) of human lung adenocarcinoma epithelial cells (A549). Carbonaceous fractions were plenteous in automobile exhaust and biomass burning, while heavy metals were more plentiful in PM 2.5 from coal combustion and automobile exhaust. The overall ranking of mass-normalized cytotoxicity for source-specific PM 2.5 was automobile exhaust > coal combustion > domestic plant biomass burning > ambient urban air, possibly with differential toxicity triggers, and showed that the carbonaceous fractions (organic carbon, OC; elemental carbon, EC) and redox-active transition metals (V, Ni, Cr) assisted by water-soluble ions (Ca 2+ , Mg 2+ , F - , Cl -) might play important roles in inducing cellular reactive organic species (ROS) production, causing oxidative stress and inflammation, resulting in cell injury and apoptosis, and thus damaging human health. Coupled with the source apportionment results of typical urban ambient air PM 2.5 in eastern China, reducing toxic PM 2.5 from these anthropogenic combustions will be greatly beneficial to public health. In addition to the air pollution control measures that have been implemented, like strengthening the vehicle emission standards, switching energy from coal to gas and electricity, and controlling the open incineration of agricultural straws, further methods could be considered, especially by preferentially reducing the diesel exhaust, lessening the coal combustion by replacement with low-ash clean coals, and depressing the rural crop straw biomass burning emissions. [ABSTRACT FROM AUTHOR]

Fine particulate matter (PM 2.5 ) is detrimental to the human respiratory system. However, the toxicity of PM 2.5 and its associated potentially harmful species, notably novel pollutants like environmentally persistent free radicals (EPFRs), remains unclear. Therefore, one-year site monitoring and ambient air PM 2.5 sampling in the Nanjing urban area was designed to investigate the relationships between chemical compositions (carbon fractions, metallic elements, and water-soluble ions) and EPFRs, and change in cytotoxicity with varying PM 2.5 components. Oxidative stress (reactive oxygen species, ROS), inflammatory injury (IL-6 and TNF-α), and membrane injury (LDH) of human lung epithelial cells (A549) induced by PM 2.5 were analyzed using in vitro cytotoxicity test. Both the composition and toxicity of PM 2.5 from different seasons were compared. The average daily exposure of urban PM 2.5 associated EPFRs load in Nanjing were 2.29 × 10 11 spin m -3 . Their exposure concentration and cytotoxic damage ability were stronger in the cold season than warm. The particle compositions of metals and carbon fractions were significantly positively correlated with EPFRs. The airborne EPFRs, organic carbon (OC), and heavy metal Cu, As, and Pb may pose principal cell damage ability, which is worthy of further study interlinking aerosol pollution and health risks., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)