Trump’s Latest Clean Air Waivers Push MATS, HON, and EtO Rules Past 2029

In another aggressive move to delay air toxics enforcement, President Trump has issued a new round of Clean Air Act (CAA) compliance waivers, granting over 100 industrial facilities—including coal plants, chemical manufacturers, sterilizers, and taconite iron ore producers—two-year exemptions from Biden-era air toxics rules.

The waivers, issued via four presidential proclamations on July 17, invoke the CAA’s rarely used emergency authority to delay compliance based on national security, energy stability, and technical feasibility. The targeted rules include:

• Mercury and Air Toxics Standards (MATS): Six more coal-fired power plants will join 68 already exempted from the 2023 MATS update, which tightened mercury and particulate limits and required continuous emissions monitoring. The compliance deadline is now effectively pushed to 2029.

• Hazardous Organic NESHAP (HON): 53 chemical plants are exempt from stricter emissions limits on ethylene oxide (EtO) and chloroprene, and from new fenceline monitoring mandates. Industry claims the monitoring requirements are infeasible and risk supply chain disruptions.

• EtO Sterilizers Rule: 39 medical sterilization facilities, including those owned by Sterigenics, are now exempt from EtO limits based on a 2016 EPA risk assessment. Trump’s proclamation warns of medical device shortages if the rule is enforced as written.

• Taconite Iron Ore Rule: All eight U.S. facilities in this sector are exempted. The administration argues that the rule relies on unproven technologies and could undercut domestic steel production critical to defense and infrastructure.

This round of waivers builds on the administration’s earlier efforts to roll back or freeze a broad swath of environmental rules. In each case, the White House cites technical impracticality and national resilience. But environmental groups say this is an illegal abuse of executive power to benefit polluters.

Earth justice and the Environmental Defense Fund (EDF) have already filed legal challenges. EDF, in particular, is suing to obtain waiver application records and contesting the legality of the exemptions in Air Alliance Houston v. Trump, pending in the U.S. District Court for D.C.

What Comes Next?

EPA is currently accepting public comment on its proposed rescission of the 2023 MATS updates, with many stakeholders urging the agency to preserve at least the continuous monitoring requirements. Meanwhile, the window for compliance under the chemical and sterilizer rules may quietly close as litigation drags on and facilities continue operations without implementing the new protections.

With these proclamations, the Trump administration isn’t just delaying enforcement—it’s signaling a broader deregulatory agenda that could outlast the current term. By using presidential waivers to bypass rulemakings, the administration may effectively defund compliance, preempt judicial review, and shift the burden to future administrations and communities downwind of industrial emitters.