This week twenty four (24) states filed a lawsuit against Federal EPA to vacate the Agency’s recently strengthened national ambient air quality standard (NAAQS) for fine particulate matter (PM2.5).   The lawsuit was filed the very same day as EPA published the rule in the Federal Register, opening a 60-day window for litigants to file petitions for judicial review. The 24 states suing EPA over the rule are: Alabama, Alaska, Arkansas, Florida, Georgia, Idaho, Indiana, Iowa, Kansas, Kentucky, Louisiana, Mississippi, Missouri, Montana, Nebraska, North Dakota, Ohio, Oklahoma, South Carolina, South Dakota, Tennessee, Utah, West Virginia, and Wyoming.  These same states urged the Biden administration before the rule was promulgated not to proceed with tougher standards.  “Petitioners will show that the final rule exceeds the agency’s statutory authority and otherwise is arbitrary, capricious, an abuse of discretion, and not in accordance with law. Petitioners thus ask that this Court declare unlawful and vacate the agency’s final action,” the States say in their suit.  EPA’s rule tightens the prior annual “primary,” or health-based standard for PM2.5 from 12 micrograms per cubic meter (ug/m3) down to 9 ug/m3.   Most believe the new standard will place many more areas into “nonattainment”  and as a result these areas must develop state implementation plans (SIPs) outlining measures to attain the limit and must impose tougher-still permitting requirements on new and modified industrial facilities.  For California, especially the San Joaquin Valley, this new standard will be problematic to meet and could trigger even tougher requirements on farm equipment and even tighter fugitive dust regulations.