**3. Results**

The demographic and clinical characteristics of the southern/ northern groups were tabulated (Table 1). While their gender, mean age, BMI and fasting glucose were similar, smoking status, SBP, DBP, metabolic syndrome and homocysteine were significantly lower, but their LDL-C, vitamin B12 and folate were significantly higher in Southern Chinese compared with the Northern Chinese (*p* < 0.0015). PM2.5 exposure in Southern China (44.0 ± 6.8 μg/m3) (Figure 1A,B) was significantly lower than in Northern China (71.1 ± 15.8 μg/m3), *p* < 0.0015. (Figure 2A,B).

**Figure 1.** (**A**) Far view of residential estates and Mount Ma On along the Shing Moon River of Shatin, Hong Kong on clear day with PM2.5 concentration of 14 μg/m3, and (**B**) on foggy polluted day with PM2.5 concentration of 45 μg/m<sup>3</sup> (Woo et al. [18]).

**Figure 2.** (**A**) Sky view of Chongqing Garden on clear day with PM2.5 concentration of 45 μg/m3, and (**B**) Chongqing residence estate near riverside on a foggy day with PM2.5 concentration of 79 μg/m<sup>3</sup> (Courtesy of Prof. YH Yin).



B12: Vitamin B12. BMI: Body Mass Index. DBP: Diastolic Blood Pressure. LDL-C: Low Density Lipoprotein Cholesterol. PM2.5: Particulate Matter <2.5 um in Diameter.
