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Area Designations for 1997 Fine Particle (PM2.5) Standards

PM2.5 Air Quality, 1999-2003

Information provided for informational purposes only Note: EPA no longer updates this information, but it may be useful for historical purposes. See the PM Designations Home Page for more recent information about PM Designations.

(Based on Seasonally-Weighted Annual Average)


The average of monitor sites has been consistently below the national annual standard of 15 μg/m<sup>3</sup>. It declined slightly from 1999 to 2003, falling approximately from 14 to 13, and the 90th percentile line has decreased from about 18 to about 15.3. The 10th percentile line has decreased slightly from 8.5 to 7.7. This summary is based on viewing the graph.
1999-2003: 10% decrease

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