PM2.5 National Ambient Air Quality Standards
Ten years later, in 1997, after a lengthy review, EPA revised the PM standards, setting separate standards for fine particles (PM2.5), equal to or less than 2.5 microns in diameter (about 1/30th the average width of a human hair), based on their link to serious health problems ranging from increased symptoms, hospital admissions and emergency room visits for people with heart and lung disease, to premature death in people with heart or lung disease.
In 1997 EPA revised the NAAQS for particulate matter and established primary (health-based) annual and 24-hour standards for PM2.5 [62 FR 38652]. The 1997 annual standard is 15.0 micrograms per cubic meter (µg/m3), based on a 3-year average of annual mean PM2.5 concentrations. The 1997 24-hour standard is 65 µg/m3, based on a 3-year average of the 98th percentile of 24-hour concentrations. [Percentile is a value on a scale that indicates the percent of a distribution that is equal to or below it. For example, a concentration value at the 98th percentile is equal to or greater than 98 percent of the concentration values.] EPA also revised the secondary standards, making them equal to the primary standards.
EPA designated 6 areas (ten counties, and 2 partial counties) in West Virginia as nonattainment with respect to the 1997 PM2.5 NAAQS.
- Charleston, WV [Kanawha and Putnam Counties];
- Huntington-Ashland, WV-KY-OH [Cabell and Wayne Counties, and the Graham Tax District in Mason County];
- Martinsburg, WV-Hagerstown, MD [Berkeley County];
- Parkersburg-Marietta, WV-OH [Wood County and the Grant Tax District in Pleasants County];
- Steubenville-Weirton, OH-WV [Brooke and Hancock Counties]; and
- Wheeling, WV-OH [Marshall and Ohio Counties].
It should be noted that all the areas designated as nonattainment were not in compliance with the annual standard of 15.0 micrograms per cubic meter (µg/m3), based on a 3-year average of annual mean PM2.5 concentrations. However, all areas of West Virginia were found to be attainment with the co-existing 1997 24-hour standard of 65 µg/m3. The design values for the West Virginia nonattainment area monitors for both the annual and 24-hour standards are presented in this Table.
In 2009 EPA determined that the Martinsburg, Parkersburg and Wheeling areas were in attainment with the 1997 standard, based on data for the 3-year period 2006-2008 [74 FR 60199].
As required by the Clean Air Act, the DAQ submitted demonstrations to EPA for incorporation into the State Implementation Plan (SIP) demonstrating that the Parkersburg, Charleston, Huntington and Weirton areas would attainment the 1997 standard by April of 2010. As shown in the Table, data for the 3-year period 2007-2009 shows that these areas did attain the standard.
In 2006, EPA revised the primary 24-hour standard for PM2.5 to 35 µg/m3, based on a 3-year average of the 98th percentile of 24-hour concentrations. EPA designated 2 areas (4 counties) in West Virginia nonattainment with respect to the 2006 24-hour standard based on data for the 3-year period 2006-2008 [74 FR 58688].
For the subsequent 3-year period, 2007-2009, the Charleston are monitored attainment with the 2006 24-hour standard as shown in the Table.
For more information on the PM2.5 NAAQS see the EPA website: