Abstract
The success of remote sensing methodology to accurately estimate ambient particulate matter (PM) on the earth’s surface has resulted in the increased use of aerosol optical depth (AOD) AOD-PM10, AOD-PM2.5, and AOD-PM1 concentration level fused surfaces in cardiovascular epidemiologic and hypothesis-testing of inflammatory physiologic studies. AOD-PM fused surfaces have served as proxies for ambient PM monitor measurements in economically developed and developing counties as well as in urban and rural areas. Since 2012, 45 published studies have evaluated the association between increased AOD-PM concentration level readings and adverse cardiovascular outcomes. Fifteen surveillance studies used inflammation as a descriptive physiologic mechanism and another 20 investigations used the inflammatory physiologic mechanism to explain how AOD-PM exposure changes the cardiovascular system. Among the remaining ten studies, nine mentioned another description and one referred to another explanation. Analyses of the published studies showed: 1) There was 81% agreement between AOD-PM2.5 readings and ambient PM2.5 monitor measurements. 2) Developing countries had higher AOD-PM2.5 readings than developed countries. 3) Descriptive physiologic inflammatory studies found positive associations between higher AOD-PM readings and more acute myocardial infarction, cardiovascular disease, and heart failure outcomes. 4) Higher AOD-PM readings were associated with abnormal blood glucose, c-reactive protein and lipids in studies that cited the inflammatory physiologic mechanism as an explanation. 5) The percentage of specific outcomes increased as the number of identified risk factors also went up only if the AOD-PM2.5 readings were higher and decreased if the AOD-PM2.5 readings were lower. 6) The inflammation description AOD-PM2.5 readings mean (43.4 μg/m3) did not differ from the inflammation explanation AOD-PM2.5 mean (32.0 μg/m3). Study results were used to update the physiologic inflammatory mechanism as a mediator of the effects of AOD-PM exposure on the cardiovascular system. The full extent of the adverse effects of AOD-PM exposure on the cardiovascular system only becomes evident when cardiovascular and other pathophysiological changes are also considered and evaluated. This review paper aims to demonstrate why AOD-PM and cardiovascular system studies are a new and useful source of information about how ambient PM exposure adversely impacts the cardiovascular system in diverse populations in different countries.