PM NAAQS Reconsideration Announcement

EPA has announced that it will reconsider the previous administration’s decision to retain the particulate matter (PM) National Ambient Air Quality Standards (NAAQS). EPA is reconsidering the December 2020 decision because available scientific evidence and technical information indicate that the current standards may not be adequate to protect public health and welfare, as required by the Clean Air Act.

The press release is available here:

More information on PM NAAQS and other relevant documents can also be accessed on our website here:

Nominations for EPA’s Mobile Sources Technical Review Subcommittee

EPA is seeking nominations from representatives of nonfederal interests such as community and/or environmental justice interests, state and local government interests, environmental advocacy groups, future transportation options and shared mobility interests, transportation, and supply chain shippers, marine and inland port interests, and mobile source emission modeling interests to serve on the Mobile Sources Technical Review Subcommittee (MSTRS; a subcommittee of the Clean Air Act Advisory Committee). MSTRS members are appointed by the EPA Administrator for three-year terms with the possibility of reappointment to a second term. The subcommittee’s website is at The Federal Register Notice announcing the request for nominations was published earlier today, and nominations must be received by August 2, 2021.

Revised Air Quality Designations for the 2015 Ozone NAAQS

In response to a July 2020, D.C. Circuit Court remand, EPA is taking action on its review of the Agency’s original designation for 16 counties for the 2015 National Ambient Air Quality Standards for ozone.  EPA is taking final action to revise the boundaries for six nonattainment areas in four states (Illinois, Indiana, Missouri and Wisconsin) and reaffirming the April 30, 2018, designation associated with Ottawa County, Michigan.  In the case of the Doña Ana County, NM and Denver Metro/North Front Range, CO nonattainment areas, upon further review, EPA intends to revise its initial designation. Because EPA’s intended designations for the associated remanded counties of El Paso, TX and Weld, CO, respectively, disagree with the states’ area recommendations, EPA is sending letters to each state opening a 120-day period for the states to provide additional information based on the existing record. The Agency will notify both New Mexico and Texas of this planned addition.  EPA is also opening a 30-day period for the public to comment. Additional information:;

EPA 120-day letter to Texas:

Technical Support Document:

FR Publication of Houston 2008 Ozone RFP SIP Final Action

The Houston 2008 Serious area Reasonable Further Progress (RFP) SIP revision was signed by the EPA Regional Administrator on April 30th. The action was published in the Federal Register on May 10, 2021 ( EPA’s approval and finding of adequacy for the 2020 MVEBs becomes effective 30 days after the date of FR publication (June 9, 2021).

FHWA Air Quality and Sustainable Transport Highlights

FHWA Highlights

The purpose of this message is to inform you that the latest issue of the FHWA Air Quality and Sustainable Transport Highlights is now available.

The Highlights provide the latest news and information on transportation related air quality and sustainability activities, including information on transportation conformity, resiliency, and other related activities.

Items of interest in this issue include:

  • FHWA announced the fifth round of Alternative Fuel Corridor designations
  • FHWA released Coupled Model Intercomparison Project Processing Tool Version 2.1 (CMIP Tool)

Past issues of the Air Quality and Conformity Highlights are available at:

Past issues of the Sustainable Transport Newsletter are available at: