McIlwain will conclude her tenure on December 31, according to an announcement from the governor's office. Deputy Secretary Adam Ortiz will serve as acting secretary starting January 1, 2027.

"Secretary McIlwain has dedicated decades of her life to public service, and her contributions will ensure that we leave our young Marylanders with more sustainable, equitable and healthy communities than the ones we inherited," Moore said in a statement.

McIlwain, who was confirmed in March 2023, previously served as under secretary at the California Environmental Protection Agency and held executive roles at the U.S. Environmental Protection Agency, including assistant regional administrator based in San Francisco. The governor's office noted she has 39 years of public service across state and federal environmental agencies.

Environmental advocates offered a mixed assessment of her tenure. They pointed to high-profile settlements with polluters, including a 2023 agreement in which the City of Baltimore paid a fine of up to $4.7 million following massive sewage releases from its two treatment plants. The settlement came after Blue Water Baltimore filed a lawsuit over the discharges.

"We had some strong legal wins in collaboration with MDE during her time as secretary, but I'm looking forward to a change," said Alice Volpitta, Blue Water Baltimore's Baltimore Harbor Waterkeeper. "I would like to see someone who is more proactive on enforcement and keeping the agency fully staffed."

Community activists were more critical, arguing that MDE failed to crack down on polluters until residents and advocates pushed for action. They cited the Curtis Bay medical waste incinerator, which had toxic air emissions and illegal releases for years before the state shut down its operations last month.

"It's being shut down because of people from this community and other communities who have fought for generations to get it shut down, and it should not have to be that way," resident David Jones said at an MDE hearing in South Baltimore last month.

In North Baltimore, residents have complained about MDE's handling of a permit for a crematorium within 200 feet of homes. The Vaughn Greene Funeral Services crematorium on York Road drew complaints shortly after opening, with residents filming visible smoke releases that violated its permit.

A scathing legislative audit released in April also flagged lackluster enforcement, documenting the agency's failure to verify inspectors issuing lead-free certificates and to ensure rentals had current lead inspection certificates. The audit disclosed a backlog of wastewater permits and inspections, with some facility inspections as much as seven years overdue.

A staffer at another prominent environmental nonprofit noted that MDE tentatively denied a permit this week for a Baltimore waste oil cleanup company seeking to expand in Curtis Bay near homes and a high school.

"Agencies don't deny permits very often, so they have done some meaningful and good things," the staffer said. "But that company has a really bad compliance history, and the community was really concerned about it for a long, long time."

The staffer said they hope the next MDE secretary will take a tougher stance on enforcement, including imposing stricter limits on pollutant emissions from Baltimore's long-controversial BRESCO trash incinerator.

"We would prefer MDE to be stronger in terms of standing up to industry pressure to weaken legislation, which is always there," the staffer said. "There's an enormous amount of industry pressure."

McIlwain's departure is part of a broader cabinet overhaul. Secretary of Emergency Management Russell Strickland will retire on December 8 after a 50-year public safety career. Montgomery County Assistant Chief Administrative Officer Earl Stoddard will serve as acting secretary starting December 9.

Last week, Moore announced three other departing cabinet secretaries: Susan Lee, secretary of state; Edward Rothstein, secretary of veterans and military families; and Carolyn Scruggs, secretary of public safety and correctional services. The governor's chief of staff, Lester Davis, will also leave after 14 months to head the Maryland Technology Development Corp.