Direct and indirect effects of particulate matter on the cardiovascular system

Human exposure to particulate matter (PM) elicits a variety of responses on the cardiovascular system through both direct and indirect pathways. Indirect effects of PM on the cardiovascular system are mediated through the autonomic nervous system, which controls heart rate variability, and inflammatory responses, which augment acute cardiovascular events and atherosclerosis. Recent research demonstrates that PM also affects the cardiovascular system directly by entry into the systemic circulation. This process causes myocardial dysfunction through mechanisms of reactive oxygen species production, calcium ion interference, and vascular dysfunction. In this review, we will present key evidence in both the direct and indirect pathways, suggest clinical applications of the current literature, and recommend directions for future research.

► Air pollution affects people both directly and indirectly.
► Direct effects involve infiltration of the endothelial lining by particulate matter, allowing direct access to the bloodstream.
► Indirect effects of air pollution involve respiratory-mediated release of inflammatory markers and/or cytokines, which enter the bloodstream.
► Mechanisms of direct and indirect effects of particulate matter are not entirely understood.