On March 29, 2007, EPA finalized the Clean Air Fine Particle Implementation Rule. This outlines requirements for state and tribal clean air plans to address high levels of particle pollution in 39 areas of the country. Info.  Fact sheet.  Final rule  (includes comments received and EPA responses to specific points). The White House OMB okayed this rule. 
- EPA: John Millett,  202-564-4355.
The Clean Air Act requires that by April 2008 state and tribal governments must develop plans to meet the 1997 standards for fine particles (PM 2.5). States are supposed to meet this standard by 2010- but in their implementation plans they can propose an attainment date extension of up to five years (to 2015).
Is your region affected? See EPA info on:
Find which officials are responsible for developing these particulate pollution plans for your state: National Association of Clean Air Agencies (formerly STAPPA and ALAPCO), email,  202-624-7864. Contacts by state. 
In clean air circles, a controversy has been brewing over how this rule might apply to power plants. Critics say the new rule appears to exempt electric power plants from a general requirement to use "reasonably available" pollution controls - if those plants are in states covered by EPA's Clean Air Interstate Rule  (CAIR). This cap-and-trade rule could enable power plants to comply with the new particulate rule by buying pollution credits, rather than installing and using pollution control equipment.
CAIR applies to both ozone and particulate emissions. It covers most of the eastern states  (except ME, VT, and NH) and the District of Columbia. It reaches as far west as TX.
If you're covering air pollution in CAIR territory, it's worth contacting utility and government sources for specifics on whether the state plans will require power plants to install or upgrade particulate controls. Also, check on local CAIR trading activity - who's selling credits, who's buying, and how does this activity mesh with upcoming state plans?