Abstract
Ambient inhalable particulate matter (PM) is a serious health concern worldwide, but especially so in China where high PM concentrations affect huge populations. Atmospheric processes and emission sources cause spatial and temporal variations in PM concentration and chemical composition, but their influence on the toxicological characteristics of PM are still inadequately understood.In this study, we report an extensive chemical and toxicological characterization of size-segregated urban air inhalable PM collected in August and October 2013 from Nanjing, and assess the effects of atmospheric processes and likely emission sources. A549 human alveolar epithelial cells were exposed to day- and nighttime PM samples (25, 75, 150, 200, 300 μg/ml) followed by analyses of cytotoxicity, genotoxicity, cell cycle, and inflammatory response.PM10–2.5 and PM0.2 caused the greatest toxicological responses for different endpoints, illustrating that particles with differing size and chemical composition activate distinct toxicological pathways in A549 cells. PM10–2.5 displayed the greatest oxidative stress and genotoxic responses; both were higher for the August samples compared with October. In contrast, PM0.2 and PM2.5–1.0 samples displayed high cytotoxicity and substantially disrupted cell cycle; August samples were more cytotoxic whereas October samples displayed higher cell cycle disruption. Several components associated with combustion, traffic, and industrial emissions displayed strong correlations with these toxicological responses. The lower responses for PM1.0–0.2 compared to PM0.2 and PM2.5–1.0 indicate diminished toxicological effects likely due to aerosol aging and lower proportion of fresh emission particles rich in highly reactive chemical components in the PM1.0–0.2 fraction.Different emission sources and atmospheric processes caused variations in the chemical composition and toxicological responses between PM fractions, sampling campaigns, and day and night. The results indicate different toxicological pathways for coarse-mode particles compared to the smaller particle fractions with typically higher content of combustion-derived components. The variable responses inside PM fractions demonstrate that differences in chemical composition influence the induced toxicological responses.
Highlights
China's rapid economic growth has led to severely elevated levels of particulate matter (PM) air pollution, which has been witnessed during recent years in phenomena such as haze and smog
Our results suggest that the toxicological responses elicited by PM1.0–0.2 were in line with those observed for PM0.2, but at lower magnitude
The PM composition and induced toxicological responses varied between the day and nighttime samples, indicating the influence of day-night variations of both atmospheric processes and emissions
Summary
China's rapid economic growth has led to severely elevated levels of particulate matter (PM) air pollution, which has been witnessed during recent years in phenomena such as haze and smog. Most harshly affected by PM pollution are the economically developed, heavily industrialized and densely populated urban areas, such as the provincial capitals (Chen and Xu, 2017). One of these capital cities is Nanjing, located in the Yangtze River Delta (YRD) region in southeastern China; it is a major industrial, commercial and educational hub of the Jiangsu province, which has recently experienced severe air pollution events. Exposure to PM2.5, particulate matter with aerodynamic diameter under 2.5 μm, was the fifth-ranking mortality risk factor globally in 2015, with an estimated 4.2 million attributable premature deaths (7.6% of total global mortality), whereof 1.1 million occurred in China (Cohen et al, 2017). The combination of high air pollution levels and high population density makes air pollution a serious threat to public health in East Asia; it has prompted new policies to counter the problem by the Chinese government
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