Fig. 1

Exposure maps for black carbon and NO₂ in Allegheny County during 2011–2012. Land use regression was applied to model pollutant concentrations as described in Methods. Left panels: represent the estimated distribution of the indicated pollutants as modeled over a grid containing cells sized at 50 m by 50 m. Pollutant concentrations are depicted over a grey scale with increasing concentrations represented by increased luminosity. The blue dots indicate the location of the Pittsburgh downtown business district, and blue arrows in the BC panel show locations of major industrial sources. An average exposure value for each census tract was calculated as the mean from all cells aggregated within that tract. Right panels show the distribution of census tract exposures divided into 4 quartiles of exposure magnitude where quartile 1 represents the least exposed and quartile 4 represents the highest