Table 8 Four high-frequent topics in the research of particulate matter and atherosclerosis

Topic 1. Epidemiological studies on the associations between tobacco exposure and atherosclerosis

Clusters 1, 3, and 9

3.5, 10.67, 4.44

Topic 2. Epidemiological studies on the associations between environmental particulate matter exposure and atherosclerosis

Clusters 2 and 4

24.44, 1.33

Topic 3. studies on the different roles of particulate matter size/components/source in health effects

Clusters 6 and 10

35.11, 7.11

Topic 4. Toxicological studies on particulate matter-induced arteriosclerosis

Clusters 5, 7, and 8

6.67, 2.67, 3.11