Hazards and Risks

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. The EPA has established the following deadlines:

• Initial monitoring: November 9, 2026
• Establishing regulated areas and ensuring compliance with the Existing Chemical Exposure Limit: February 8, 2027
• Ensuring the methods of compliance as well as developing and implementing an exposure control plan: May 10, 2027

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 Ethyl acetate, Ethyl acetate/Isopropanol mixtures, and Acetone. Specific recommendations can be found in the resource links below.

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.