There are presently 37 areas that violate
the current PM-10 standard. The form of the PM-2.5 standard requires
that the 3-year average (rounded to the nearest 0.1 ug/m3) of
the annual means from single monitors or the average of multiple
monitors must be at or below the level of the annual standard
and the 3-year average (rounded to the nearest 1 ug/m3) of the
ninety-eighth percentile values at each monitor cannot exceed
the level of the daily standard. In determining attainment of
the annual average standard, an area may choose to use either
the spatially averaged concentrations across all population-oriented
monitors or it may use the highest 3-year average based on individual
monitors. The annual PM-2.5 standard (2012) is 12 ug/m3. The
level of the 24-hour PM-2.5
standard (2006) is 35 micrograms per cubic meter (µg/m3).
of the EPA's PM-10 and PM-2.5 designations for nonattainment
can be reviewed by clicking here.