Association of short-term exposure to black carbon or elemental carbon (black circles) and particulate matter < 2.5 μm in diameter (open circles) with arrhythmia recorded on implantable cardioverter defibrillator or electrocardiogram, per interquartile range increase in mean (or median) pollutant concentration (in μg/m3). Studies are organized by endpoint (VA, AF, SVE, discharges, any arrhythmia), population type (i.e., healthy, pre-existing disease, older adults) and averaging time. Circles represent point estimates and horizontal lines represent 95% confidence intervals. BC = black carbon; EC = elemental carbon; h = hour; IQR = interquartile range; MA = moving average; PM2.5 = particulate matter < 2.5 μm in diameter; VA = ventricular arrhythmia; AF = atrial fibrillation; SVE = supraventricular ectopy; VE = ventricular ectopy.