National PM2.5 Concentration Spatial Pattern Contact: Stefan Falke, Background and Rationale Annual Average PM2.5 Concentrations ( ) Seasonal Maps of PM2.5 ( ) PM2.5 Map Uncertainty Resource Links

Annual PM2.5 concentration maps are useful in identifying potential non- attainment areas of the PM2.5 NAAQS (annual average of 15 μg/m 3 ) Point monitoring data are used to estimate PM2.5 mapsestimate PM2.5 maps The limited number of PM2.5 monitoring data requires the application of surrogate data (PM10 and Visibility) in the mapping process Background & Rationale

This is a work in progress. The maps are currently the best available but are expected to change as estimation methods improve and additional data is incorporated. Visibility Aided PM2.5PM10 Aided PM2.5 PM2.5 concentrations are above 15 μg/m 3 in the San Joaquin Valley and South Coast Basin of California. Pittsburgh, St. Louis, Roanoke, and an area stretching from New York City to Washington D.C. are above 15 μg/m 3 in both maps. The visibility aided estimates indicate a larger region above 15 μg/m 3 along the eastern seaboard. Additional areas above 15 μg/m 3 are shown with PM10 aided estimates including Atlanta and eastern Tennessee. Annual Average PM2.5 Concentrations ( )

Visibility-Aided PM 2.5 PM 10 -Aided PM 2.5 Annual average PM 2.5 concentrations are above 15 μg/m 3 in the San Joaquin Valley and South Coast Basin of California. Annual average PM 2.5 concentrations in Pittsburgh, St. Louis, Roanoke, and an area stretching from New York City to Washington D.C. are above 15 μg/m 3 in both maps. The visibility- aided estimates indicate a larger region above 15 μg/m 3 along the eastern seaboard. Additional areas above 15 μg/m 3 are shown with PM 10 -aided estimates including Atlanta and eastern Tennessee. Annual Average PM 2.5 Concentrations ( ) Key reference: capita (visibility and PM10 data are used as surrogate variables for PM 2.5 in estimating PM 2.5 concentration maps )

PM 10 -and visibility-aided PM 2.5 maps have similar overall patterns but contain distinct differences in some areas. For instance, the visibility-aided PM 2.5 concentrations are more than 5 μg/m 3 higher than PM 10 -aided estimates in Texas, Michigan, and the eastern seaboard. The differences between the two maps is one indication of the uncertainty in the estimation of PM 2.5 concentrations. Where the two maps are similar, the PM 2.5 concentration estimates are more certain than in areas of large differences. Differences between visibility- and PM 10 -aided annual estimates PM 2.5 Map Uncertainty

Seasonal Maps of PM2.5 ( ) The PM2.5 peaks during the summer, Q3, in the Eastern US. The PM2.5 peaks in the winter, Q1, in populated regions of the Southwest and the San Joaquin Valley.

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