Company Announcements

With less than a year until key compliance deadlines, time is running out for chemical manufacturers to act

LITTLE ROCK, Ark.--(BUSINESS WIRE)--Sep. 9, 2025-- Montrose Environmental Group, Inc. (NYSE: MEG), is on a mission to help protect the air we breathe, the water we drink, and the soil that feeds us to enhance environmental stewardship while supporting economic development. The company is currently engaged in more than 30 projects nationwide to help chemical manufacturers prepare for the upcoming Hazardous Organic NESHAP Maximum Achievable Control Technology (HON MACT) regulation. These efforts span emissions testing, compliance strategy, and monitoring implementation—all designed to support facilities facing deadlines that begin in mid-2026. With less than a year remaining, Montrose is helping clients navigate complex requirements and avoid costly delays.

The HON MACT rule, finalized by the U.S. Environmental Protection Agency in 2024, targets hazardous air pollutants emitted by synthetic organic chemical manufacturing and polymer and resin facilities. The regulation introduces stricter controls on ethylene oxide (EtO), chloroprene, and other air toxics, with the goal of reducing community-wide cancer risks by up to 96%.¹ Key compliance deadlines include July 15, 2026, for fenceline monitoring and EtO control requirements, and July 15, 2027, for corrective actions and broader equipment upgrades.

“HON MACT is one of the most important air regulations in recent history for chemical manufacturers. With long equipment lead times and limited service capacity, the time to act is now,” said Todd Grosshandler, Chief Commercial Officer at Montrose Environmental Group. “This rule is part of a broader wave of regulations reaffirming clean air as a basic right. Montrose brings together regulatory expertise, advanced laboratory and testing capabilities, and deployed field teams across a broad geographic footprint to help clients not only meet the rule—but lead the way in environmental responsibility.”

Montrose offers a full suite of end-to-end emissions and air testing capabilities, including fenceline monitoring with both real-time and integrated sampling solutions, stack testing, ambient air quality monitoring, leak detection and repair (LDAR), flare efficiency assessments, and compliance program development—supported by the only accredited laboratory in the nation our team of scientists and engineers works closely with clients to deliver tailored solutions that meet regulatory requirements and operational goals.

To learn more about how Montrose can support your HON MACT compliance strategy, visit HON MACT Best Practices | Montrose Environmental.

¹ https://www.epa.gov/newsreleases/biden-harris-administration-finalizes-stronger-clean-air-standards-chemical-plants

Additional HON MACT Resources

HON MACT Compliance: Lessons Learned in Refinery Method 325 Sampling Programs
Beyond Compliance: How Smart Facilities Are Getting Ahead of the HON Rule
HON Compliance Workshop Recap: Why Pilot Studies Matter Now

About Montrose

Montrose is a leading environmental solutions company focused on supporting commercial and government organizations as they deal with the challenges of today and prepare for what’s coming tomorrow. With ~3,400 employees across 100+ locations worldwide, Montrose combines deep local knowledge with an integrated approach to design, engineering, and operations, enabling Montrose to respond effectively and efficiently to the unique requirements of each project. From comprehensive air measurement and laboratory services to regulatory compliance, emergency response, permitting, engineering, and remediation, Montrose delivers innovative and practical solutions that keep its clients on top of their immediate needs – and well ahead of the strategic curve. For more information, visit www.montrose-env.com. Follow us on LinkedIn.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Forward-looking statements may be identified by the use of words such as "intend," "expect", and "may", and other similar expressions that predict or indicate future events or that are not statements of historical matters. Forward-looking statements are based on current information available at the time the statements are made and on management’s reasonable belief or expectations with respect to future events, and are subject to risks and uncertainties, many of which are beyond the Company’s control, that could cause actual performance or results to differ materially from the belief or expectations expressed in or suggested by the forward-looking statements. Additional factors or events that could cause actual results to differ may also emerge from time to time, and it is not possible for the Company to predict all of them. Forward-looking statements speak only as of the date on which they are made, and the Company undertakes no obligation to update any forward-looking statement to reflect future events, developments or otherwise, except as may be required by applicable law. Investors are referred to the Company’s filings with the Securities and Exchange Commission, including its Annual Report on Form 10-K for the year ended December 31, 2023, for additional information regarding the risks and uncertainties that may cause actual results to differ materially from those expressed in any forward-looking statement.

View source version on businesswire.com: https://www.businesswire.com/news/home/20250909886044/en/

Investor Relations
Adrianne Griffin
(949) 988-3383
ir@montrose-env.com

Media Relations
Tammy Hovey
(917) 520-2751
pr@montrose-env.com

Source: Montrose Environmental Group, Inc.