By Jessica Coomes
The Environmental Protection Agency is crediting the Clean Air Interstate
Rule and other emissions reduction programs with cutting emissions of nitrogen
oxides and sulfur dioxide, helping to improve air quality in Eastern states.
The average eight-hour ozone concentrations from 2008 to 2010 in states in
the Eastern half of the country that are subject to CAIR were 16 percent lower
than average from 2001 to 2003, after accounting for weather variations,
according to an EPA progress
report on CAIR, the former nitrogen oxides budget trading program, and the
acid rain program.
Fine particulate matter concentrations have dropped 22 percent in the warm
season and 13 percent in the cool season during the same period, after
accounting for the weather, according to the report.
EPA continues to administer the CAIR program to reduce emissions of nitrogen
oxides and sulfur dioxide from power plants in the East. The agency promulgated
a replacement program, the Cross-State Air Pollution Rule, but the U.S. Court of
Appeals for the District of Columbia Circuit has stayed it while legal
challenges play out (EME Homer City Generation L.P. v. EPA, D.C. Cir.,
No. 11-1302, oral arguments 4/13/12).
EPA administered the nitrogen oxides budget trading program from 2003 to 2008
under a cap-and-trade program to address interstate transport of nitrogen
oxides, which was called the “NOx SIP Call.”
Congress established the acid rain program under Title IV of the Clean Air
Act Amendments of 1990. Sulfur dioxide and nitrogen oxides are the primary
precursors to acid rain.
The May progress report credited the three emissions reductions programs for
helping to reduce pollution in areas of Eastern states found to be in
nonattainment of the 1997 ozone and fine particulate matter national ambient air
The ozone attainment designations were based on air quality data from 2001 to
2003, and 91 areas in the East were in nonattainment. Air quality data from 2008
to 2010 shows 90 of those areas report ozone concentrations that are below the
1997 standard of 0.08 part per million.
For fine particulate matter, 36 Eastern areas were in nonattainment of the
1997 standard, based on 2001 to 2003 data. Today, 2008 to 2010 data show 34
areas with concentrations below the standard of 15 micrograms per cubic
EPA said the three programs have been “a significant contributor” in the air
The progress report is available at http://www.epa.gov/airmarkets/progress/ARPCAIR_downloads/ARPCAIR10_environmental_health.pdf.