On June 15, 2012, U.S. EPA proposed stricter standards to the National Ambient Air Quality Standards (NAAQS) under the Clean Air Act for fine particulate matter. The proposed rule, which is the result of a lawsuit in the U.S. Court of Appeals in the Washington D.C Circuit brought by environmental groups and certain states, proposes to tighten the annual standard for particulate matter under 2.5 microns (PM 2.5) from 15 micrograms per cubic meter (ug/m3) (the 2006 standard) to between 12 and 13 ug/m3. The rule also proposes a new separate standard for improving visibility in urban areas of either 28 to 30 "deciviews," a measurement of visibility. The proposed rule and "fact sheets" provided by the Agency make clear that EPA is not proposing a change to the existing 24-hour and secondary standards for fine and course particulate matter set in 2006.

EPA claims that the new standard will come at an annual cost of between $2.9 million and $69 million (depending upon a final standard of 12 or 13 ug/m3), but claims these costs are outweighed by alleged health benefits of $220 million to $5.9 billion. EPA is also claiming that all but six counties in the United States should be able to meet the new standards without additional action. However, San Bernadino and Riverside Counties in California, Santa Cruz County in Arizona, Wayne County in Michigan, Jefferson County in Alabama, and Lincoln County in Montana - are all expected to need to reduce fine particulate emissions to attain the new standards.

Under state and federal Clean Air Act regulations, counties that are out of attainment with the NAAQs can be subject to special "Retro-active Control Technology" (RACT) requirements, and new sources of fine particulate emissions will need to obtain "offsets" prior to construction among other requirements.

In addition to the new proposed standards, EPA is also proposing changes to monitoring requirements for fine particulate matter including the addition of fine particulate ambient air monitors especially along urban highways.

EPA's proposed rule comes during an election year and is expected to draw broad criticism from Republicans and industry groups. Environmental groups are already praising the new proposed lower standards. The new proposed rule has not yet been published in the Federal Register. Comments on the new proposed rule are due within 63 days of publication in the Federal Register and can be submitted through http://www.regulations.gov. The proposed rule and related fact sheets can be viewed at http://www.epa.gov/pm/actions.html.