Air Pollution Index (PCA readme file)

CANUE specialists developed multi-pollutant indices of air quality. Three-year (2012-14) average datasets of trace gases and aerosols derived from satellite-based sensors were prepared for a common 10x10 km grid over North America (NA: Canada and the United States), including surface PM2.5 (in µg/m3) , NO2, SO2, CO and NH3 (all in ppb), and vertical column totals for HCHO (formaldehyde in molecules per cm2). Surface O3 concentrations from CANUE holdings (warm season average 8 hr max) were merged with these satellite-based data. Principal Component Analysis (PCA) was used to compute three pollutant mixture indicators for each 10x10 km grid. These values were normalized to a 0-100 scale. Each indicator is related to a different aspect of common air pollution mixtures occurring across North America (Canada and the U.S.).Indicator 1 (PC1) reflects combustion-related pollutant mixtures, typically linked to populated areas. PC1 is suggested for use as the primary multi-pollutant, long-term outdoor air pollution exposure index because it incorporates the largest diversity of pollutants (PM2.5, CO, NO2, formaldehyde (HCHO), SO2, NH3 and O3, listed here in order of their PCA loading coefficients (e.g., weights)).Indicator 2 (PC2) is related to O3 NH3 mixtures common in parts of western NA linked to higher elevations (i.e., background O3) and livestock grazing. Indicator 3 (PC3) is related to NH3 mixtures (e.g., with some weight from CO and PM2.5) associated with more intensive agricultural practices (e.g., crops, intensive raising of animals).Also included are the input air quality datasets.CANUE staff indexed the data to DMTI Spatial single-link postal codes.