What does the new EPA methylene chloride rule mean for academic labs?

On April 30, the US Environmental Protection Agency finalized a rule that prohibits nearly all uses of methylene chloride. To the relief of many academic chemists, the EPA carved out a number of exceptions to the ban, including the solvent’s use as a laboratory chemical.

But upon closer inspection of the regulation, researchers in the US are realizing that to keep using methylene chloride in their labs, they will need to conduct baseline monitoring and implement strict workplace safety measures—all in about a year.

The short timeline presents a challenge, says Christopher Kolodziej, a chemical hygiene officer at the University of California, Los Angeles. He’s fairly confident that larger schools will be able to make it work, but “I’m less confident on behalf of some of the smaller institutions out there,” he says.

Case in point: a chemistry professor at a primarily undergraduate institution, who asked to remain anonymous because of their pretenure status, says they were recently told by their chemical safety officer that they will no longer be allowed to use methylene chloride in their research or teaching labs starting in the fall.

“From an academic standpoint, it’s happening very quickly,” the professor says. “I wish they would have given researchers more time.”

Methylene chloride, known in academia as dichloromethane or DCM, is one of the most widely used laboratory solvents because of its polarity, aprotic structure, and low boiling point. These properties mean chemists frequently reach for it to synthesize, extract, and purify compounds.

“We keep a 19 L drum of DCM because we use it so much,” says Mark Olson, a chemistry professor at Texas A&M University–Corpus Christi.

Despite its popularity, methylene chloride can be dangerous to work with. A 2022 risk assessment conducted by the EPA found that long-term exposure to the chemical can cause liver, lung, breast, and brain cancers, as well as cancers of the blood and central nervous system. Acute short-term exposure can lead to lung irritation, liver dysfunction, neurotoxicity, and even death.

For those permitted to continue using DCM, the EPA’s new regulation aims to prevent these health hazards by mandating that the workplaces implement the agency’s Workplace Chemical Protection Program (WCPP). The program’s stipulations include requirements to measure workers’ initial exposure levels by May 2025 and monitor periodically at least once every 5 years.

But since the EPA first proposed the regulation in 2023, academics, environmental health and safety (EH&S) professionals, and the American Chemical Society have expressed concerns about many elements of the WCPP. The society, for example, says in a public comment to the EPA that following the program “would be extremely challenging for academic institutions to implement and would negatively impact research and teaching.”

C&EN is published by ACS but is editorially independent.

In addition, many of these groups claim that adhering to the WCPP could create confusion as research labs scramble to comply with it alongside the Occupational Safety and Health Administration (OSHA) standards they’re already subject to.

“It’s just going to become confusing to have multiple agencies promulgating different limitations or requirements for EH&S or the research staff,” says Brent Cooley, the deputy director of environmental health and safety for the University of California Office of the President.

Double standards

Since 1991, research labs have followed OSHA’s Occupational Exposure to Hazardous Chemicals in Laboratories standard (29 C.F.R. 1910.1450). The regulation, known as the laboratory standard, protects lab workers who handle hazardous chemicals in much smaller quantities than they would in an industrial setting.

One of the standard’s main requirements is that labs develop a chemical hygiene plan to address how to safely procure, store, handle, and dispose of chemicals. Notably, it supersedes OSHA’s more industry-focused substance-specific standards except for their exposure limits and, if those limits are exceeded, monitoring requirements dictated by those standards (J. Chem. Health Saf. 2016, DOI: 10.1016/j.jchas.2015.10.015).

This setup acknowledges that it would be unrealistic to “have different standards for every chemical in a lab and then try to comply with all of them,” says Kristi Ohr, assistant director of academic safety at the University of Massachusetts Amherst. Labs also have certain safety features, such as fume hoods, that significantly reduce worker risk. “It’s not exactly the same as an industrial setting where maybe you don’t have those things,” Ohr says.

But with DCM, the EPA appears to be interpreting the laboratory standard differently. The agency has suggested that labs should be following the other requirements outlined by the substance-specific regulations, including initial exposure monitoring followed by periodic testing.

This new interpretation gives Ohr and Kolodziej pause, especially as many aspects of the WCPP are aligned with OSHA’s industry-focused methylene chloride standard (29 C.F.R. 1910.1052), which universities are generally not set up to follow.

“If EPA believes that we’re subject to the full [OSHA methylene chloride] standard, we feel that they’re potentially going to miscalibrate and think that the rules that they’re proposing aren’t that much more burdensome,” Kolodziej says.

Uneven impact

It’s hard for researchers and EH&S staff to gauge just how the methylene chloride regulation will affect university labs since the EPA has yet to publish its guidance document specifying how to comply with the WCPP. According to an agency spokesperson, that information will be available “in the next few weeks.”

The EPA has provided some details in the interim. In a June 4 webinar, the agency said research labs can use existing chemical hygiene plans to fulfill some of the documentation requirements listed in the WCPP. It also clarified that universities can group similar activities when doing methylene chloride exposure monitoring, reducing the number of samples needed.

“That’s helpful,” Ohr says. “However, in and of itself, it’s still going to be a lot.”

Larger schools can spread the work among their robust EH&S offices. The University of California’s Cooley says the UC system has over 500 EH&S staff.

Smaller institutions don’t have those resources. For example, Laura Dwyer, the chemistry lab coordinator at the University of Mount Union, is also the sole chemical hygiene officer at her school.

Because she holds multiple roles, Dwyer has limited time to figure out any new methylene chloride–related logistics. “Chemical hygiene is only a part of my job,” she says in an email. She’s also responsible for prepping the undergraduate labs, doing all department purchasing, hiring and managing lab assistants, and being available to answer student and faculty questions.

Then there’s the matter of cost. “Like most smaller liberal arts schools, money is tight these days,” Dwyer says. “If we do want to figure out compliance with the EPA requirements, that will be a cost that may need to be justified to the administration.”

According to Anthony Pitagno, ACS’s director of government affairs, the proper monitoring equipment could cost several thousand dollars.

Furthermore, if an institution doesn’t already have someone on staff with the expertise to conduct exposure monitoring, it will probably have to contract these services, Pitagno says in an email. “It will be a huge financial burden for universities as a typical contract would cost $10,000 or more.”

Finding alternatives

These hurdles might explain why the pretenure professor’s school has decided that, for now, the best option is to phase out methylene chloride from its research and teaching labs. Time will tell whether EH&S departments at other small universities follow suit.

At Mount Union, for example, Dwyer is adopting more of a wait-and-see approach. “If the EPA releases clear guidelines that tell me specifically what I need to do, that will go a long way towards convincing me that it’s worth it to set up a monitoring program,” she says.

But even without institutional mandates, some individual researchers, such as Olson at Texas A&M, are thinking about eliminating DCM from their labs. “I don’t want to burden our EH&S more than we already have,” he says. He also doesn’t want to put his students’ health at risk.

Depending on what a researcher needs DCM for, good alternatives may exist, says Kyle Grice, a chemistry professor at DePaul University. Grice, who is also thinking about phasing out the solvent from his lab, points to a 2012 paper that explored replacing DCM in chromatography for sustainability reasons (Green Chem., DOI: 10.1039/C2GC36064K).

But switching out DCM used in synthetic reactions will likely be a bigger headache. “It depends on how lucky you are,” Grice says. “Some reactions are very robust and can be done with a few different solvents, no problem. Some reactions are so solvent specific they will only work in one or two solvents.”

Unfortunately, not every researcher will immediately know which camp their specific reactions fall in. So “now you’re spending a summer trying to revise your labs to not have DCM in them,” Grice says. “That’s going to be tough.”

Adding to the difficulty is that researchers need to avoid making what the EPA refers to as “regrettable substitutions.” In the finalized rule, the agency recommends “careful review of the available hazard and exposure information on the potential substitutes to avoid a substitute chemical that might later be found to present unreasonable risks or be subject to regulation.”

For instance, some potential substitutes have physical hazards that DCM does not. “If we all switch to THF [tetrahydrofuran] or similar molecules, you’ve got to worry about peroxide formation in all your stuff,” Grice says by way of example. Such peroxides are highly unstable and have resulted in lab explosions in the past.

Chloroform is another possible alternative, Ohr says. But she remembers when DCM was once presented as the “kinder, gentler alternative for chloroform.”

Olson, meanwhile, says his lab is considering dichloroethane, though he acknowledges “that this is another compound that may have an ill-fated destiny, like DCM, in the fullness of time.”

In fact, 1,1- and 1,2-dichloroethane are 2 of 20 high-priority chemicals the EPA is evaluating under the Toxic Substances Control Act. The risk assessments have yet to be completed.

More to come

Methylene chloride is not the first solvent that chemists have had to pivot away from. Both benzene and carbon tetrachloride were once as ubiquitous in the lab as DCM is today.

But times have changed, and the two compounds have largely faded out of use now that researchers know how dangerous they are. That tells Grice that chemists will be able to mostly eliminate DCM.

The EPA is looking to regulate more compounds in the future, however, which prompts Dwyer to ask, “Is this going to be a thing now? EPA creating separate monitoring requirements for specific chemicals beyond what is required by the OSHA Laboratory Standard?”

Cooley is also concerned. “If they’re requiring or having slightly different controls or requirements for each chemical, it’s just going to get incredibly complex,” he says.

That’s not to say that anyone is objecting to the idea of lowering exposure limits as new information about health hazards comes to light, Kolodziej stresses. And he’s confident that labs can meet the EPA’s new exposure limits for methylene chloride—which are an order of magnitude lower than OSHA’s—using existing standard practices like fume hoods.

But it feels to Kolodziej almost as if history is repeating itself. It was only 30 years ago that academic research groups had to comply with all of OSHA’s substance- specific standards before the government “realized that this overall approach was not well tailored to labs,” he says.

“The lab standard works,” Ohr says. “I wish the EPA had just considered that a little more.”