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Environmental Health and Safety

Methylene chloride

Hazards and risks

Methylene chloride, also known as dichloromethane or DCM is a volatile, colorless liquid that has a moderately sweet aroma. 

Being highly volatile and heavier than air makes methylene chloride a serious inhalation hazard.  Acute inhalation will cause central nervous system depression, unconciousness, and even death.  Once inside the body, methylene chloride is metabolized to formaldehyde and carbon monoxide so that chronic exposure may produce symptoms similar to carbon monoxide exposure. Symptoms may include headache, nausea, vomiting, confusion, and dizziness.  Skin contact may cause irritation and burns. In addition, methylene chloride is a suspect carcinogen.

Regulatory Compliance

The EPA Methylene Chloride Rule under Section 6(a) of the Toxic Substances Control Act  published in 40 CFR Part 751 Subpart B went into effect on July 8, 2024.  This regulation applies to the use of methylene chloride in research laboratories. The Rule establishes an action level of 1 ppm vapor concentration averaged over an 8-hour workday. To prevent occupational exposure to methylene chloride and comply with this regulation, all users of methylene chloride in USC laboratories must develop and/or complete the following:

  1. EH&S Chemical and Laboratory Safety training.
  2. EH&S Hazardous Waste training.
  3. Written standard operating procedure (SOP) or Exposure Control Plan (ECP) for the specific use of methylene chloride in your laboratory.
  4. In-house lab-specific training that includes a discussion on methylene chloride SDS, SOP/ECP and all controls that need to be implemented to prevent exposure to methylene chloride.  

Guidelines for Safe Use 

1. Hazard Awareness

Be aware of the dangers of methylene chloride, including its health effects (e.g., neurotoxicity, carcinogenicity), symptoms of exposure (e.g., dizziness, headache, nausea), and safety requirements. Read the Safety Data Sheet (SDS) and understand the content of your written SOP/ECP.

2. Substitution

Methylene chloride is commonly used as a solvent in laboratories for extractions, chromatography, reactions, and other applications. Substitutes should be selected based on the specific use, as alternatives may vary in effectiveness, safety, and environmental impact. Always evaluate compatibility with your process through testing. Common greener alternatives include:

  • For chromatography and purification: Mixtures like 3:1 ethyl acetate:ethanol, or propan-2-one (acetone)/cyclopentane. Ethyl acetate alone or combined with toluene, heptane, or acetonitrile can also replace DCM in many cases.
  • For extractions: Ethyl acetate/ethanol mixtures, water/acetonitrile blends, or bio-based options like limonene, ethyl lactate, and dimethyl carbonate for lower toxicity and biodegradability.
  • For paint stripping or specialized cleaning: N-methyl pyrrolidone (NMP) as a pollution prevention alternative.
  • General solvent-free or reduced-hazard approaches: Implement solvent-free protocols where possible, or use safer options like acetone/heptane for reactions and purifications.

Review resources for detailed tables and application-specific guidance such as the Green Chemistry Teaching and Learning Community, DCM replacement overview,  Rutgers University's alternative solvents list,  Teledyne Isco's chromatography-focused replacements , U Penn's fact sheet on solvent alternatives, and Science Direct's articles on eco-friendly substitutions..

3.  Hazard-specific Training and Competency

Demonstrate competency in following your methylene chloride SOP/ECP and the associated scientific methodology through training, practice, and adherence to protocols.

4. Engineering Control
  • Use methylene chloride only inside a functioning fume hood or in a closed system designed to prevent the escape of vapors.
  • If using outside of a fume hood, contact Environmental Health & Safety (EH&S) at (803) 351-9874.
  • Avoid production of aerosols when handling the liquid.
5. Personal Protective Equipment (PPE)
  • Wear proper lab attire and a laboratory coat.
  • Use properly fitted safety goggles (unvented if methylene chloride is used outside of a fume hood).
  • Use gloves that are resistant to methylene chloride (e.g., “Silver Shield”, polyvinyl alcohol, Viton). For improved dexterity, double glove by donning a nitrile glove over a methylene chloride-resistant glove.
  • Remove gloves properly by not touching the contaminated side, then wash hands with soap and water.
6. Storage Requirements
  • Store only in closed and sealed containers (avoid storage in squirt bottles, beakers, flasks, etc., as they allow vapors to escape).
  • Keep away from aluminum metal, oxidizers, strong acids, and amines.
7. Spill Response
  • Immediately clean up spills of methylene chloride contained in a fume hood.
  • If spilled outside of a fume hood, evacuate the area and call EH&S at (803) 777-5269 or (803) 727-5706 for assistance.
8. Waste Management
  • Collect waste in a designated "Methylene Chloride Only" waste container.
  • Label, store, and dispose of methylene chloride waste according to the USC Hazardous waste policy.

 

Resources

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