EPA declares Berrien and Muskegon ozone areas in attainment

The U.S. Environmental Protection Agency has determined that the Berrien County and Muskegon County, Michigan nonattainment areas have attained the 2015 ozone National Ambient Air Quality Standards, suspending their obligation to submit attainment demonstrations and associated planning requirements. The final rule was published in the Federal Register of Friday, 9 October 2026, under docket EPA–R05–OAR–2026–1354, and takes effect the same day. The action amends the Michigan identification-of-plan table at 40 CFR 52.1170(e).

The determination, informally known as a clean data determination, rests on complete, quality-assured and certified ambient air monitoring data for the 2023–2025 design value period. The 2015 ozone standard was set at 0.070 parts per million. The rule also relies on an exceptional events request submitted to the EPA by the Michigan Department of Environment, Great Lakes, and Energy (EGLE) on 26 December 2025, which the agency concurred with on 12 January 2026.

What the determination suspends

For as long as both areas continue to attain the 2015 ozone standard, the EPA suspends the following requirements:

• Attainment demonstrations.
• Reasonably Available Control Measures (RACM).
• Reasonable Further Progress (RFP) plans.
• Contingency measures for failure to attain or make reasonable progress.
• Other planning State Implementation Plans related to attainment of the 2015 ozone standard.

The suspension ends if the areas are redesignated to attainment, at which point the requirements no longer apply, or if the EPA determines the areas have failed to meet the standard, at which point the requirements return and the plans must be submitted within a timeframe set by the agency.

Wildfire smoke and the comment record

The EPA proposed the determination on 12 March 2026 and opened a 30-day comment period that closed on 13 April 2026. Three comments were received: one adverse, from the Great Lakes Environmental Law Center (GLELC), and two generally supportive.

The dispute centred on the exclusion of wildfire smoke-impacted ozone data at the Muskegon and Coloma monitors, linked to distant Canadian fires. Commenters argued that Michigan had not shown wildfire smoke was the proximate cause of the exceedances and that local industry and vehicles were responsible. The EPA rejected those objections, defending its weight-of-evidence approach and citing the Sixth Circuit decision in Sierra Club v. EPA, 161 F.4th 934 (2025), which upheld the agency’s method for evaluating exceptional events.

Deadlines and legal exposure

• Effective date: 9 October 2026, immediate upon publication under 5 U.S.C. 553(d)(1).
• Deadline for petitions for judicial review: 8 December 2026, filed in the appropriate U.S. Court of Appeals.
• Serious area attainment date: 3 August 2027.

Should monitoring data for 2024–2026 show that either area is violating the 2015 ozone standard, the EPA would be obligated under Clean Air Act section 181(b)(2) to find that the areas failed to attain by the Serious area attainment date; they would then be reclassified by operation of law to the next higher classification and the clean data determinations would be rescinded. The rule was signed on 25 September 2026 by Anne Vogel, Regional Administrator for Region 5, and the docket is administered by Neena Nallaballi of the Air and Radiation Division in Chicago.

The determination relieves western Michigan regulators and industry of a substantial planning workload, but the relief is conditional and reversible: the EPA retains the power to reinstate the suspended requirements if air quality deteriorates before the 2027 attainment date.

Source: Federal Register, Vol. 91, No. 195, 9 October 2026, Rules and Regulations, p. 64623 (official reference: 2026-20736).