A US appeals court has struck down a key Environmental Protection Agency (EPA) rule banning all consumer and most industrial uses of the solvent dichloromethane (DCM), also known as methylene chloride (MC). The development comes after research labs across the country that routinely use the chemical – estimated to be in the thousands – have been working to comply with the agency’s now-cancelled DCM risk management rule for more than two years.
In a long-awaited decision on 15 September, the appeals court voided the DCM rule issued under former President Biden in 2024 and sent the matter back to the EPA. The regulation had mandated that federal and non-federal labs put in place DCM exposure monitoring by 9 November 2026 and meet stricter exposure limits by 8 February 2027.
The three judges unanimously rejected the EPA’s ‘whole chemical’ approach under which the agency concluded that almost all uses of DCM pose an ‘unreasonable risk of injury to health’ and argued that the agency ‘ignored’ widespread use of personal protective equipment.
Rather than this ‘whole chemical approach’, the court held that the rule requires the agency to base its risk determinations on individual conditions of use. ‘EPA’s risk analysis yielded extraordinarily small limits for both acute and chronic exposures to MC,’ the court concluded. The ruling added that the agency’s results ‘lack epidemiological support, reflect selective use of data and failures to consider alternative acceptable data, and were based on unrealistic benchmark margins of error’. Overall, the court concluded that this analysis was ‘arbitrary and capricious, lacking substantial evidence, and contrary to law’.
Besides being widely used in academic organic chemistry labs, DCM was also a commonly used as a degreaser and paint stripper in the US. Exposure to the chemical was linked to dozens of deaths in the country between 1980 and 2018, primarily related to consumer and professional paint removal. The EPA notes that DCM is neurotoxic and can cause heart and liver damage, as well as various cancers.
The court ruling does not affect the EPA’s 2019 rule that prohibited consumer use of DCM chloride in paint strippers, which remains in force.
The American Chemistry Council (ACC), which represents US chemical companies, celebrated the court ruling. ‘For years, ACC has maintained that [the toxic substances control act (Tsca)] requires EPA to evaluate and manage risk based on individual conditions of use and the best available science, including consideration of existing workplace protections and real-world exposure information,’ the trade group stated, emphasising that the appeals court agreed.
Tim Barton, an industrial hygienist and chief safety officer at a US academic medical centre, has concerns about the ruling, however. He notes that academic research labs and many other organisations rely on regulations, consensus and professional standards to establish the standard of care for their personnel. ‘We value safety and commit the time and resources necessary to ensure compliance. Changes are often necessary and help us to do the best with what information is available,’ Barton tells Chemistry World. ‘Sea changes in the role of regulatory agencies and court perspectives introduces uncertainty, and potential inefficiencies – such as the allocation of limited resources to support exposure assessments, policy and plan development, training resources,’ he warns.
Concerns voiced from other corners
According to Barton, one of the challenges of the EPA’s final DCM rule was that it marked a shift at the agency into an arena occupied by the Occupational Safety and Health Administration – regulatory exposure limits. ‘There was a lot of uncertainty about how this would be interpreted and enforced,’ he says. ‘The latest ruling is another step in a changing landscape.’
Russ Phifer, former chair of the American Chemical Society division of chemical health and safety and executive director of the National Registry of Certified Chemists, says he was surprised by the court ruling. He notes that the courts have rarely intervened in EPA rules on the basis of insufficient evidence of risk to health. But Phifer points out that many labs already have these DCM restrictions in place, have found alternatives to DCM and are unlikely to revert to widespread use of the chemical. ‘The fact that there were variances for small-quantity laboratory use means that there are now no incentives to continue with any efforts to replace DCM if they hadn’t already done so,’ he says.
Some in the research community were surprised when President Trump’s EPA appeared back the Biden DCM rule last year. But Phifer doubts that the EPA will appeal the court’s ruling. ‘The Trump administration is generally trying to get rid of regulations, not institute new ones,’ he says. ‘There was a mandate for them to evaluate DCM through TSCA, so they had to respond.’
However, the legal decision could be challenged by environmental and chemical safety advocacy groups. ‘Congress updated Tsca in 2016 so that EPA could finally take action to get dangerous chemicals like methylene chloride out of our homes and workplaces,’ stated Liz Hitchcock, who directs federal policy at the US-based non-profit Toxic-Free Future. ‘This ruling sides with the chemical industry at the expense of public health and will put more people at risk of serious harm.’
