Methylene Chloride Guidance

Main Content

Overview
Methylene Chloride – also known as dichloromethane (DCM) - is a common solvent used in research, industry, and some consumer products. In academic research labs it’s valued for its strong solvency and low boiling point.

Background
In April 2024, the U.S Environmental Protection Agency (EPA) issued a final rule under the Toxic Substance Control Act (TSCA) regulating methylene chloride (CAS No. 75-09-2). This rule affects all Texas Christian University (TCU) operations that use DCM, including research, academic, and maintenance activities. 

Health risks:
Because DCM is highly volatile, inhalation is the primary exposure route. Health effects can include:

• Cancer risk: Increased risk with prolonged exposure (based on animal studies). 
• Neurotoxicity: Headache, dizziness, confusion. 
• Organ effect: Potential impacts to the heart, liver, and nervous system. 
• Irritation: Skin and eye irritation on contact. 
• Asphyxiation risk: High concentration in poorly ventilated areas can displace oxygen.

New exposure limits (EPA, 2024)
The EPA rule significantly lowers allowable workplace exposure compared with previous Occupational Safety and Health Administration (OSHA) limits.  

Exposure Limits	Previous OSHA	New EPA Rule
8-hour Time-Weighted Average (TWA)	25 ppm	2 ppm
15 –minute Short-Term Exposure Limit (STEL)	125 ppm	16 ppm
Action Level	12.5 ppm	1 ppm

What this means: Exposures that were once considered acceptable may now require stronger controls –e.g., improved ventilation, more frequent monitoring, adjusted work practices, and/or personal protective equipment (PPE). 

How can your lab minimize DCM exposure?
The best way to minimize DCM exposure and provide a safe environment for researchers are to replace it where possible, reduce quantities where possible, and unitize appropriate engineering controls when its use is necessary. 

Replacement Solvents
Below are potential alternatives to methylene chloride / DCM, with selected, application-specific references. For additional substitution guidance, consult the American Chemical Society Tools for Innovation in Chemistry.  

Application	DCM Alternatives	Selected References
Extraction and chromatography	Ethyl Acetate, Heptane, Toluene, 2-MeTHF, Methyl tert-butyl ether	Green Chemistry Tools  Replacement Solvents for DCM in Chromatography  Alternative: Extraction and Purification  UPenn Fact Sheet: Solvent Alternatives
Peptide synthesis	2-MeTHF, Ethyl Acetate	Green Solid-Phase Peptide Synthesis
Various organic synthesis reactions	Reaction dependent	Alternatives in Organic and Medicinal Chemistry  Greener Solvent Alternatives, Sigma-Aldrich

Reduction

• Reduce quantities of DCM used in applications where it is utilized when possible.
• Only purchase quantities of DCM that will be used in a reasonable amount of time (a few months as imposed to an entire year or more). 
• If your lab has DCM that is no longer in use and will not be used, submit a waste pickup request to safety@tcu.edu.  

Engineering Controls 

• Lab use of DCM in chemical fume hoods and any other “closed” systems (where DCM cannot evaporate to the lab atmosphere) will protect the health and safety of our researchers and mitigate many of regulatory requirements from the EPA regulation. Move all activities using DCM to a chemical fume hood. 
• Store DCM in appropriate chemical storage cabinets and dispense DCM from larger containers in chemical fume hoods. 
• Collect and keep all DCM-containing waste in chemical fume hoods. 
• If instrumentation and equipment (using DCM) is not a closed system, and/or is too large to fit inside a chemical fume hood, other forms of engineering controls should be pursued (e.g., sealed tops of waste vessels, sealing leak points, snorkel hoods placed over “open to atmosphere” points, etc.) where possible. 
• In cases where the use of chemical fume hoods is not possible. Principal Investigators (PIs) must notify EHS and generate an alternative exposure control plan for approval prior to initiating work. Air monitoring, at the laboratory’s expense, may be needed to confirm that this results in the desired effect. 
  

Steps for Complying with EPA Standard
To determine whether researchers may be exposed to unsafe levels of dichloromethane (DCM) and what
mitigation is required, the University will conduct initial exposure monitoring for personnel who work with
DCM. Environmental Health & Safety (EHS) needs your assistance to understand DCM use at TCU and to identify where monitoring is needed.

What you need to do:
1.) Complete the DCM Use Survey
         All laboratories must respond – even if DCM is not used or is used only minimally.
2.) EHS review and scheduling
         EHS will review responses and, if indicated, contact your lab to arrange personal breathing-zone (PBZ) air
          sampling.
3.) Initial monitoring
         Monitoring may take place throughout 2025 to address evolving assessments of the regulation and
          institutional safety standards.
4.) If exposures exceed action levels
         EHS will partner with your lab and Facilities to develop a Workplace Chemical Protection Program
          (WCPP), implement engineering/administrative controls and PPE, and perform follow-up and periodic
          monitoring to verify that controls are effective and to maintain compliance with EPA requirements. 

Resources & Forms
Methylene Chloride Workplace Chemical Protection Plan (WCPP) Template (work in progress)
EPA Final Rule: Regulation of Methylene Chloride Under TSCA
EPA FACT SHEET: Final Risk Management Rule for Methylene Chloride Under TSCA (pdf)
EPA COMPLIANCE GUIDE: Regulation of Methylene Chloride Under TSCA (pdf)
Effort to Replace Methylene Chloride in Pharmaceutical Process Chemistry
OSHA Methylene Chloride Standard
OSHA Methylene Chloride Overview