CO = carbon monoxide; kg/yr = kilogram per year; NOx = nitrogen oxides; PM2.5 = fine particulate matter; PM10 = coarse particulate matter; SO2 = sulfur dioxide; VOC = volatile organic compound
Note: Annual emissions of lead, polycyclic aromatic hydrocarbons, and polychlorinated dioxins and furans were too small to fit on the same axes.
Source: National Pollutant Inventory