On May 14, 2026, the EPA proposed delaying Tier 4 by two model years, citing industry feasibility concerns. This is Part 1 of a two-part review; Part 2 may result in permanent changes to or elimination of the standards entirely. The proposed delay means millions more vehicles will be sold at higher pollution levels that we already know cause preventable illness and death.
A critical point often overlooked: Vehicles sold in model years 2027 and 2028 under weaker Tier 3 standards will remain on the road for 15 to 20 years. Every model year of delay is not a two-year gap in health protection. It is a two-decade tail of preventable harm that will be felt in our communities, our hospitals, and our children’s lungs long after these vehicles roll off the lot.
There are a couple of ways you can take action:
1. Submit a written comment here or at regulations.gov, Docket ID No. EPA-HQOAR-2025-3297. Deadline: July 6, 2026.
2. Raise awareness by sharing this toolkit with 5 colleagues and encouraging them to take action.
