A Colorado dentist has sounded the alarm about mercury fillings in prisoners. He was fired hours later, according to a whistleblower lawsuit.

A dentist working at two Colorado prisons claims in a new whistleblower lawsuit that he was fired after raising concerns about the state Department of Corrections’ continued use of mercury-containing dental fillings.

Dentist Charles Hardin was fired April 4, hours after he emailed the DOC’s dental chief, a registered nurse and a psychologist to suggest the prison system change its approach to such fillings to align with federal recommendations, the lawsuit filed last week in Denver District Court alleges.

Hardin, who became a contract dentist for the DOC in late 2023, worked primarily on La Vista Correctional Centera women’s prison, and San Carlos Correctional Institutiona prison with a specialized population of inmates who have complex medical needs. Both prisons are located in Pueblo.

Hardin was concerned that the prison system’s default approach to dental treatment was to use mercury amalgam, which is a mixture of mercury and other metals, for dental procedures such as fillings. THE The US Food and Drug Administration in 2020 warned that mercury fillings pose a risk of harm to certain patients, including pregnant and breastfeeding women, people who want to become pregnant in the future, and people with certain pre-existing medical conditions.

The FDA found that mercury-containing fillings, which have commonly used for more than a centuryreleased small amounts of mercury vapor over time with regular wear and that while the vapors are usually not harmful, they can cause problems for high-risk patients.

Hardin was concerned that the prison system was over-relying on mercury amalgam when “safer alternative materials” were available and when at-risk or mentally ill inmates could not knowingly consent to the dangers of the mercury mixture, according to the lawsuit.

“The closed and institutional environment of a correctional facility further heightens these concerns because inmate patients have limited access to outpatient dental care, limited choice of alternative restorative materials, and often lack the necessary clinical monitoring or diagnostic testing to identify or manage potential mercury exposure,” the lawsuit states.

A spokeswoman for the Colorado Department of Corrections, Alondra Gonzalez, did not return a request for comment Tuesday.

Hardin emailed Michael Hale, the corrections department’s chief of dentistry, on April 4 about his concerns.

“I am concerned with how the CDOC … mandates that I am in violation of current FDA guidance on the selection of dental materials,” he wrote in the 1 p.m. email included in the lawsuit. “I would like some guidance on whether I should comply with the CDOC regulations … and go against the current FDA regulations.”

He was fired at 5:58 p.m. that same day, according to the lawsuit. The contracting company he worked for told him corrections officials felt he wasn’t a good fit, according to the complaint.

One of Hardin’s attorneys, Michael Kuhn, said Tuesday that Hardin had no warning he was going to be fired and noted that a co-worker emailed him the day before he was fired and said she expected to see him at work “next week.”