Spatial Gradients - Incorrect Statements in CD -
On page E-9, the CD states “analyses of recent data from the PM2.5 monitoring network show reasonable site-to-site correlation in most cities studied over distances of 20 to 50 km. This indicates that in such cities the concentration at a community air-monitoring site (or the average of several such sites) will provide an adequate representation of the concentration outside a home.”
This line of reasoning occurs in Chapters 5, 8, and 9. There were no scientific data presented to show that correlations instead of absolute differences among monitors is what is important.