Abstract
Traffic-related particulate matter (PM) is a major source of outdoor air pollution worldwide. It has been recently hypothesized to cause cardiometabolic syndrome, including cardiovascular dysfunction, obesity, and diabetes. The environmental and toxicological factors involved in the processes, and the detailed mechanisms remain to be explored. The objective of this study is to assess the current scientific evidence of traffic-related PM-induced cardiometabolic syndrome. We conducted a literature review by searching the keywords of “traffic related air pollution”, “particulate matter”, “human health”, and “metabolic syndrome” from 1980 to 2018. This resulted in 25 independent research studies for the final review. Both epidemiological and toxicological findings reveal consistent correlations between traffic-related PM exposure and the measured cardiometabolic health endpoints. Smaller sizes of PM, particularly ultrafine particles, are shown to be more harmful due to their greater concentrations, reactive compositions, longer lung retention, and bioavailability. The active components in traffic-related PM could be attributed to metals, black carbon, elemental carbon, polyaromatic hydrocarbons, and diesel exhaust particles. Existing evidence points out that the development of cardiometabolic symptoms can occur through chronic systemic inflammation and increased oxidative stress. The elderly (especially for women), children, genetically susceptible individuals, and people with pre-existing conditions are identified as vulnerable groups. To advance the characterization of the potential health risks of traffic-related PM, additional research is needed to investigate the detailed chemical compositions of PM constituents, atmospheric transformations, and the mode of action to induce adverse health effects. Furthermore, we recommend that future studies could explore the roles of genetic and epigenetic factors in influencing cardiometabolic health outcomes by integrating multi-omics approaches (e.g., genomics, epigenomics, and transcriptomics) to provide a comprehensive assessment of biological perturbations caused by traffic-related PM.
Highlights
Ambient air pollution is a major environmental cause of the global burden of diseases, leading to the development of chronic and acute respiratory diseases, lung cancer, cardiovascular diseases (CVD), metabolic syndrome, and cardiometabolic-associated health outcomes such as obesity and diabetes [1,2,3]
The objective of this study is to provide an up-to-date overview on the associations between traffic-related particulate matter (PM) and cardiometabolic syndrome, with a focus on cardiovascular health outcomes, metabolic dysfunction, obesity, and diabetes
After reviewing the papers with the eligibility criteria, 25 independent studies were identified that were directly related to traffic-related PM and cardiometabolic health effects (Figure 1)
Summary
Ambient air pollution is a major environmental cause of the global burden of diseases, leading to the development of chronic and acute respiratory diseases, lung cancer, cardiovascular diseases (CVD), metabolic syndrome, and cardiometabolic-associated health outcomes such as obesity and diabetes [1,2,3] These health outcomes can be largely attributed to traffic emissions resulting from rapid urbanization and increased traffic loads within the past few decades [4,5]. Smaller particles, such as fine particles (PM2.5 , less than 2.5 μm in diameter) or ultrafine particles (UFP, less than 0.1 μm in diameter) can deposit deeply into the lungs, and they cannot be cleared up by the respiratory system [8,9] These small particles may even directly penetrate the bloodstream to enter the circulation system [10] and reach various target organs (e.g., lung, heart, liver and brain) [8], which can trigger systemic health effects.
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