On March 12,
2008, the EPA announced that a new primary 8-hour ozone standard
was 0.075 parts per million (ppm) and the new secondary standard
was set at a form and level identical to the primary standard.
The previous primary and secondary standards were identical 8-hour
standards, set at 0.08 ppm.
However,
on September 16, 2009,
the EPA announced it would reconsider the 2008 national ambient
air quality standards (NAAQS) for ground-level ozone for both
human health and environmental effects. The Agency planned to
propose any needed revisions to the ozone standards by December
2009 and issue a final decision by August 2010. On January 7,
2010, the EPA announced on its web site its proposal to strengthen
the national ambient air quality standards for ground-level ozone.
The EPA's proposal decreased the 8-hour “primary” ozone
standard level, designed to protect public health, to a level
within the range of 0.060-0.070 parts per million (ppm). EPA
also proposed to establish a distinct cumulative, seasonal “secondary”
standard, referred to as the W126 index, which was designed to protect
sensitive vegetation and ecosystems, including forests, parks,
wildlife refuges, and wilderness areas. EPA proposed to set the
level of the W126 secondary standard within the range
of 7-15 ppm-hours. On August 20, the Agency announced that it
would delay its final announcement to on or around the end of
October. In early November, the EPA announced that it would reach
a final decision on the ozone standards by December 31, 2010.
On December 8, the EPA announced that it would delay its final
decision on the ozone standards until July 2011. EPA announced
on July 26 that it would not make a decision on the ozone standards
by its previously announced deadline of July 29. On September
2, 2011, President Obama requested that the EPA withdraw its
proposed revisions to the ozone standards. The proposed revisions
resulted from a reconsideration of the identical primary and
secondary ozone standards set at 0.075 ppm in March 2008.
The schedule, based on EPA's recent decision,
is now as follows:
Proposed Reconsidered NAAQS - January 2010
Final Reconsidered NAAQS - August 2010
States make recommendations for areas to be designated attainment,
nonattainment, or unclassifiable - January 2011
EPA makes final area designations - July 2011
Nonattainment designations become effective - August 2011
State Implementation Plans, outlining how states will reduce
pollution to meet the standards, are due to EPA - December 2013
States are required to meet the primary standard, with deadlines
depending on the severity of the problem - 2014 - 2031
