MIT evacuated a building Wednesday after a spill involving dimethyl mercury, an extremely potent neurotoxin. MIT’s Emergency Management department posted a message Saturday afternoon saying that a “single individual in a chemistry laboratory” went to a local emergency room and claimed to have synthesized dimethyl mercury.

Read more Cambridge Day’s 2026 state election preview

The Emergency Management post said the student remained under medical supervision, but an initial blood test showed no signs of mercury exposure. It also said the building with the laboratory, Building 18, would remain closed at least through Sunday as efforts continued to ensure it is decontaminated. The building is in a part of the campus bounded by Ames Street, Massachusetts Avenue, Memorial Drive and Vassar Street.

Mercury is dangerous to humans, and dimethyl mercury especially so – in 1997, a researcher working with it died a few months after being exposed to a few drops of the substance. Its main practical application is in calibrating nuclear magnetic resonance equipment.

An email to the MIT Chemistry Department obtained by Cambridge Day began “Dear Chemistry Colleagues” and thanked them for cooperating in the shutdown of Building 18. The email said the student exposed to dimethyl mercury worked in the Wendlandt lab, which is led by Alison Wendlandt, an associate professor of chemistry at MIT whose research includes methods for synthesizing chemical catalysts. The email said dimethyl mercury “was not part of any MIT research program, and its presence in the lab was unauthorized.”

The email further said members of the Wendlandt lab and any other people who had been on the second floor of the lab had been contacted for surveillance testing and there were other efforts to engage in contact tracing. MIT was also offering surveillance testing to anyone who had been in a common area such as a bathroom or conference room on either the second or fifth floors of Building 18 for more than a few minutes.

The Cambridge Fire Department responded to a call just after 9:30 p.m. Wednesday, city spokesman Jeremy Warnick confirmed on Saturday. He said via email “The surrounding area was surveyed by various Cambridge Fire meters and appeared to be clear. Information provided by MIT indicated a small amount of dimethyl mercury spilled inside a hood.”

Read more In Middlesex DA race, one-time colleagues in fierce fight

Another “Dear Chemistry Colleagues” email was circulating on reddit and X (formerly Twitter), purportedly sent Friday by Matthew D. Shoulders, head of MIT’s chemistry department. The email said Triumvirate Environmental, a Somerville company that provides environmental services, had worked overnight to decontaminating the building and those efforts were continuing. It stated that MIT does not allow dimethyl mercury to be purchased or synthesized.

It also said the risk of exposure was believed to be low.

It could not be confirmed whether the incident was related to a patient who checked into Mass General Wednesday night after what was reported as “exposure to a chemical substance.” The Boston Fire Department’s Hazmat team came to the hospital.

An MIT spokesperson responded to Cambridge Day’s request for comment by directing it to the Emergency Management post.

This post was updated to clarify that mercury is a neurotoxin, and to note that Building 18 building is in a part of the campus bounded by Ames Street, Massachusetts Avenue, Memorial Drive and Vassar Street.

Read more The worm stomping wood turtle is smarter than you think