Exposures to low-levels of fine particulate matter are associated with acute changes in heart rate variability, cardiac repolarization, and circulating blood lipids in coronary artery disease patients

Exposure to air pollution is a major risk factor for cardiovascular disease, disease risk factors, and mortality. Specifically, particulate matter (PM), and to some extent ozone, are contributors to these effects. In addition, exposures to these pollutants may be especially dangerous for susceptible populations. In this repeated-visit panel study, cardiovascular markers were collected from thirteen male participants with stable coronary artery disease. For 0-4 days prior to the health measurement collections, daily concentrations of fine PM (PM2.5) and ozone were obtained from local central monitoring stations located near the participant's homes. Then, single (PM2.5) and two-pollutant (PM2.5 and ozone) models were used to assess whether there were short-term changes in cardiovascular health markers. Per interquartile range increase in PM2.5, there were decrements in several heart rate variability metrics, including the standard deviation of the normal-to-normal intervals (lag 3, -5.8%, 95% confidence interval (CI) = -11.5, 0.3) and root-mean squared of successive differences (five day moving average, -8.1%, 95% CI = -15.0, -0.7). In addition, increases in PM2.5 were also associated with changes in P complexity (lag 1, 4.4%, 95% CI = 0.5, 8.5), QRS complexity (lag 1, 4.9%, 95% CI = 1.4, 8.5), total cholesterol (five day moving average, 2.1%, 95% CI = -4.1, -0.1), and high-density lipoprotein cholesterol (lag 2, -1.6%, 95% CI = -3.1, -0.1). Comparisons to our previously published work on ozone were conducted. We found that ozone affected inflammation and endothelial function, whereas PM2.5 influenced heart rate variability, repolarization, and lipids. All the health changes from these two studies were found at concentrations below the United States Environmental Protection Agency's National Ambient Air Quality Standards. Our results imply clear differences in the cardiovascular outcomes observed with exposure to the two ubiquitous air pollutants PM2.5 and ozone; this observation suggests different mechanisms of toxicity for these exposures.