EPA Tightens Air Quality Standards For Fine Particles

Revised ambient air quality standard could require more stringent control of fine particulate matter emissions.

On December 14, the U.S. Environmental Protection Agency (EPA) finalized its rule tightening the National Ambient Air Quality Standards (NAAQS) for fine particles emitted by a wide variety of sources, including power plants, industrial facilities, and gasoline and diesel engines. EPA is also making certain changes to its Prevention of Significant Deterioration permitting program with respect to the NAAQS revisions. The rule will become effective 60 days after its publication in the Federal Register, which is expected to occur early in 2013. The rule is one of several rules in recent years tightening the NAAQS for certain pollutants, resulting in additional compliance planning for states and potential clean air permitting complications for major new construction projects.

Background

The federal Clean Air Act (CAA) directs EPA to establish and periodically review and revise (as appropriate) NAAQS for the substances EPA identifies as "criteria pollutants," with the goal of protecting public health and welfare. The criteria pollutants include particulate matter, measured as both fine and coarse particulate matter (PM). Fine particulate matter consists of particles less than or equal to 2.5 micrometers in diameter (PM2.5), while coarse particulate matter consists of particles with diameters of less than or equal to 10 micrometers (PM10). For each criteria pollutant, EPA establishes primary standards to prevent any adverse impact on human health, and secondary standards to prevent adverse public welfare effects, such as on climate, vegetation, and visibility. Standards also take into consideration the duration of pollutant exposure and are expressed on a short-term basis (such as a 24-hour or shorter standard) and on a long-term basis (such as an annual standard).

Following issuance of new or revised standards, EPA (with state input) must designate areas as either meeting or not meeting the NAAQS (areas are designated "attainment" or "nonattainment" areas, respectively), and states must thereafter develop implementation plans to achieve the NAAQS, including, potentially, by adopting new rules limiting emissions. EPA last reviewed and tightened the PM NAAQS in 2006 and, among other changes, ratcheted down the primary 24-hour PM2.5 standard from 65 to 35 micrograms per cubic meter (µg/m3), while retaining the annual PM2.5 standard of 15...