**1. Introduction**

Atherosclerotic diseases (stroke and heart attack CVS) are currently the most important global health hazard, including for mainland China, which is now in a rapid phase of modernization [1,2]. Traditional atherosclerosis risk factors, including smoking, hypertension, diabetes mellitus, hyperlipidemia, obesity and physical inactivity, have been implicated [3]. Recently the detrimental association of air pollution (AP) with CVS in modernized society has been realized. In particular, small particulate matter less than 2.5 μm in diameter (PM2.5) has been associated with cardiovascular morbidity and mortality [4–6]. Of the 7 million premature deaths each year linked to air pollution (PM2.5), 34% were related to ischemic heart disease, 26% to respiratory disease and 20% were due to stroke [7].

The pathobiology of PM2.5-related atherosclerotic disease may involve direct effects of PM2.5 on cardiovascular system and/ or indirect effects of PM2.5 mediated by oxidative

**Citation:** Woo, K.; Lin, C.; Yin, Y.; Guo, D.; Chook, P.; Kwok, T.C.Y.; Celermajer, D.S. The Impact of Air Pollution (PM2.5) on Atherogenesis in Modernizing Southern versus Northern China. *Atmosphere* **2021**, *12*, 1552. https://doi.org/10.3390/ atmos12121552

Academic Editors: Duanyang Liu, Kai Qin and Honglei Wang

Received: 29 September 2021 Accepted: 8 November 2021 Published: 24 November 2021

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stress and vascular inflammation [8,9]. In other words, PM2.5 can act as a trigger in susceptible persons, or it can contribute to long-term atherogenic processes. On this issue, we and others have previously documented the negative impact of long-term PM2.5 exposure on atherosclerosis surrogates (brachial endothelial dysfunction FMD and carotid intima-media thickening IMT), which are closely linked to cardiovascular and stroke outcome [10–12].

In the past three decades, China has been undertaking a process of rapid economic development and modernization [13]. This started from the Southern seashore region and the greater Pearl Delta Bay area, and later moved to the Northern parts of the country, with different PM2.5 pollution exposure. The present study aimed to evaluate the impact of PM2.5 pollution on atherogenic process in Southern compared with Northern China.
