Figure 1From: Statistical air quality predictions for public health surveillance: evaluation and generation of county level metrics of PM2.5for the environmental public health tracking networkSpatial coverage of monitoring and modeled air quality data. “Blue cross sign” = Site Locations; “dotted rectangular red” = Census Region: “pink rectangle = County Boundary: “smaller blue square = 12-km Grid: big gray square = 36-km Grid.Back to article page