Overview

Methylene chloride, also commonly known as dichloromethane (DCM), is a colorless liquid and volatile chemical with a sweet odor. It is a fairly common solvent used in a host of consumer and commercial applications including adhesives, sealants, degreasers, and paint strippers as well as a common solvent found in many research laboratories. 

Historically, the Occupational Safety and Health Administration (OSHA) has identified methylene chloride as a toxic and hazardous substance under 1910 Subpart Z and established requirements for employers to manage occupational exposure. The Environmental Protection Agency (EPA) has recently evaluated methylene chloride under section 6(b) of the Toxic Substance Control Act and found that methylene chloride presents unreasonable risk of injury to the health of potentially exposure individuals (for more information see EPA Risk Management for Methylene Chloride) which was published in May 2024 and establishes a number of critical milestones starting in 2025.

While under the EPA rule, limited and controlled use of methylene chloride is permitted for research purposes, it establishes a significantly more stringent framework to ensure the safe use of methylene chloride.

What are the hazards associated with methylene chloride?

Methylene chloride exposures have been well correlated with increased cancer risk from both acute and chronic exposures, both by inhalation and dermal exposure routes. Methylene chloride has been associated with additional health hazards, including neurotoxicity effects, heart and liver damage, and skin or eye irritation.

How has methylene chloride exposure risk management changed under the new EPA rules?

The new EPA rules significant lower the exposure limits for methylene chloride relative to the OSHA standard.

The EPA Risk Management Rule applies to neat methylene chloride as well as mixtures containing methylene chloride at concentrations greater than 1%.  To mitigate the ongoing testing requirements triggered by higher exposure levels, all use of methylene chloride and methylene chloride containing mixtures (>1%) in research spaces will be limited to operations that do not exceed action level (1ppm).

Workplace Chemical Protection Program (WCPP)

To meet the conditions of use for methylene chloride under the new EPA rule, use of methylene chloride as a laboratory chemical must have a prepared Workplace Chemical Protection Program (WCPP). The WCPP is a written program intended to protect potentially exposed persons in the workplace, which share some similarities to management of methylene chloride under the OSHA Methylene Chloride Standard, but there are some notable differences. The WCPP defines the following requirements:

• Occupational exposure limit: Existing Chemical Exposure Limit (EPA-ECEL), Short Term Exposure Limit (EPA-STEL), and Action Level (EPA-AL)
• Defining monitoring requirements, initial and periodic
• Establishing regulated area
• Development and communication of an Exposure Control Plan
• Selection Criteria for Respiratory Protection and Personal Protective Equipment
• Management of Training
• Managing Record Keeping

EHS will work with laboratories authorized to work with methylene chloride to prepare and manage their WCPPs.

Roles within the WCPP

To help navigate the complexity of the WCPP and ensure that all required sections are met, the following model will be used to construct the WCPP. 

1. Exposure Control Plan – an institutional Exposure Control Plan shall be prepared and maintained by EHS to capture several key administrative elements specific to chemical specific WCPPs, including exposure limits, monitoring protocols, posting requirements for regulated areas, selection criteria for PPE, documenting laboratory operations, and conducting and documenting training and serving as an extension of the institutional Chemical Hygiene Plan.
2. Particularly Hazardous Substance Use Authorization – the high priority chemicals are typically associated with hazards that would be dually regulated as an OSHA Particularly Hazardous Substance (PHS), in continuance with the practice for OSHA PHS, labs are required to have an approved PHS Use Authorization prior to introduction of these materials into the research space as well as changes in use.
3. Standard Operating Procedures – a standardized template provided by EHS that additional contains written procedures that describe the lab specific uses of the chemical requiring a WCPP.
4. A matrix for tracking training completion shall be provided as part of the EHS provided standard operating procedure template.

Key Timelines

Key Timelines for Meeting Requirements of the EPA Final Rule on Methylene Chloride

• As soon as possible, laboratories interested in being assessed for continuing the use of methylene chloride or methylene chloride reagents containing greater than 0.1% methylene chloride should complete the methylene chloride questionnaire.
  • Surveys should be submitted by April 1, 2025, for inclusion in initial reviews and exposure assessments.
  • Labs that are not proceeding with authorization to continue use of methylene chloride will be expected to dispose of any methylene chloride or methylene chloride containing reagents by May 5, 2025.
  • Questionnaire is available at: EPA TSCA High Priority Chemicals
• As soon as possible and before May 1, 2025, labs should submit drafts of the PHS Use Authorization, including clear written protocols describing use of MC in the lab.
• EHS will review submit written protocols and arrange for a time to conduct initial exposure assessments.
  • Prior to initial exposure assessment, EHS may work with lab to revise protocols to address applications that will likely exceed exposure limits.
  • EHS will continue to work with laboratories that exceed action level (1ppm) to minimize exposure risk.
• Before August 1, 2025, all use of methylene chloride in research labs must be documented to be within exposure limits.
• Before October 30, 2025, WCPPs must be in place for all use of methylene chloride in research laboratories.

An amended version of this process will continue to be used as new labs seek authorization to use methylene chloride or as laboratory use changes (any new request or change in use submit after April 1, 2025.

• Prior to initiating use of methylene chloride or altering intended use, labs should submit drafts of the PHS Use Authorization and written procedures for EHS review.
• Following authorization and within 30 days if initiating new activity with methylene chloride, EHS will conduct initial exposure monitoring.
• EHS will work with laboratories as needed to ensure that within 90 days of initiating new activity, use can be confirmed to be within exposure limits.

Key Considerations

The following section lists some key considerations for laboratory uses of methylene chloride that should be followed to minimize the likelihood that a viable WCPP cannot be developed.

• Use of methylene chloride and methylene chloride containing reagents must be contained in fume hood or other approved exhausted enclosure.
  • Including all forms of reagent dispensing (manual/pour, pump, or solvent system) and rotary evaporators (rotavaps) and similar devices for solvent removal.
• Non-manufacturer containers must be labeled with GHS compliant labels.
• Methylene chloride and methylene chloride containing reagents may not be kept in open containers, such as squeeze bottles and nebulizers.
• Due to the technical challenges of safely handling large containers of methylene chloride, purchase and storage of methylene chloride in quantities greater than 1gal (4L) will generally be discouraged. Use of these larger containers will require review as a separate laboratory operation.