Three Environmental Protection Agency employees in Denver are among 139 workers who on Thursday were placed on administrative leave for signing a letter that was critical of administrator Lee Zeldin and his oversight of the agency.

Two employees in the EPA’s Region 8 headquarters in Denver and one who works at the EPA’s National Enforcement Investigations Center in Lakewood are under investigation for signing the letter, said Kate Tribbett, vice president of the American Federation of Government Employees Local 3607, which represents Region 8 employees.

The “Declaration of Dissent” letter, which was sent to Zeldin on Monday, was published on the Stand Up for Science website, and it shows at least 13 current and retired Region 8 employees as signatories.

The letter accuses Zeldin of undermining the agency’s mission to protect the environment and human health.

“It’s an interesting way to celebrate Independence Day to put people on administrative leave for using their First Amendment right to speak freely,” said Britta Copt, president of Local 3607.

It appears the signatories who serve as union officers or stewards have not been placed on leave, Copt said. Those who have taken early retirement or a buyout have not been affected by the administrative leave.

The employees on leave will be investigated for using government time and computers to sign the letter, Copt said. The union will defend those employees’ rights to free speech and is demanding the EPA recall the workers and end the investigation, she said.

EPA press secretary Brigit Hirsch wrote in a statement to The Denver Post that the agency “has a zero-tolerance policy for career bureaucrats unlawfully undermining, sabotaging and undercutting the administration’s agenda as voted for by the great people of this country last November.”

Region 8 administrator Cyrus Western, who was appointed by President Donald Trump, personally spoke to the three who were placed on leave, Tribbett said. Those who were in the office were escorted out of the building by security, she said.

“That is very unusual and only done in the past when the employee was thought to be a threat,” Tribbett said.

The notice sent to employees said they would be on paid administrative leave until July 17, pending an investigation, according to a copy obtained by The Post. It did not explain why the employees were under investigation.

“During the time you are on administrative leave, you will not experience any loss in benefits or pay. You are required to provide a current email address and phone number so that we can contact you as part of our investigation,” the letter stated.

“Please verify your contact information with the individuals included on this email immediately. You will be expected to be available at the phone number provided above (and/or by any additional or alternative contact information you provide) during your regular duty hours in accordance with your currently approved work schedule should the agency need to contact you.”

The “Declaration of Dissent” letter, which was signed by 230 people and copied to Congress, accuses Zeldin of undermining the EPA’s mission of protecting human health and the environment.

“Since the agency’s founding in 1970, EPA has accomplished this mission by leveraging science, funding and expert staff in service to the American people,” the letter states. “Today, we stand together in dissent against the current administration’s focus on harmful deregulation, mischaracterization of previous EPA actions, and disregard for scientific expertise.

“Since January 2025, federal workers across the country have been denigrated and dismissed based on false claims of waste, fraud and abuse. Meanwhile, Americans have witnessed the unraveling of public health and environmental protections in the pursuit of political advantage.”

It lays out five areas of concern: undermining public trust, ignoring science to benefit polluters, environmental justice, dismantling the EPA’s Office of Research and Development and creating a culture of fear.

Under Zeldin’s leadership, the EPA has reduced employment across the country, cut funding for environmental justice, proposed repealing rules that limit emissions from coal-fired power plants, frozen grants for clean energy projects and tried to undo a ban on asbestos.

Cindy Beeler, a former energy adviser in the Region 8 office, said she signed the letter because Zeldin and Trump are eroding the EPA’s important role in the United States. She said similar moves in other agencies, such as the National Institutes of Health, also worry her.

“The attack on science has been happening for years and years and years now,” Beeler said.

The EPA’s Office of Research and Development was world-renowned for its work on environmental problems. During her career, Beeler said it was the EPA’s research on methane that led to national policy that directed oil and gas companies to reduce emissions at their drilling sites.

“Without that emissions data, you can’t make a rule,” she said. “Scientific research has been shut down. You can’t just pick it back up in a month or a year and say, ‘Let’s start those Petri dishes again.’ ”

The Associated Press contributed to this report.