EPA Restrictions for Methylene Chloride/Dichloromethane (DCM)

In April 2024, the Environmental Protection Agency (EPA) determined that DCM poses an unreasonable risk to human health and issued a final rule under the Toxic Substance Control Act (TSCA). This rule bans most consumer and commercial uses of DCM due to its health risks.

While the new rule allows continued use in research labs under certain conditions, it requires that labs adhere to a Workplace Chemical Protection Program (WCPP) to limit exposure and ensure safe handling.

It’s paramount that labs using DCM follow the Required Actions for UCSF Labs.

Due to its high volatility, inhalation exposure to vapors is a significant hazard of working with DCM. Exposure to DCM can cause both short-term and long-term health effects, including:

• Cancer risk – Based on animal studies, prolonged exposure can increase cancer risk.
• Neurotoxicity – Symptoms such as headaches, dizziness, and confusion.
• Organ damage – Potential harm to the heart, liver, and nervous system.
• Irritation – Skin and eye irritation upon contact.
• Asphyxiation risk – High concentrations in poorly ventilated areas can lead to oxygen deprivation.

The new EPA regulation significantly lowers the allowable exposure levels for DCM compared to Cal/OSHA’s previous standards (see table below). For context, the new eight-hour time-weighted average (TWA) for DCM exposure is 2 ppm, which is 12.5 times lower than the previous Cal/OSHA limit of 25 ppm. This means that even low-level exposure that was previously considered acceptable will now require enhanced protective measures, such as improved ventilation, increased monitoring, adjustments to work practices, and/or the use of personal protective equipment (PPE).

Chemical Synthesis and Sample Preparation

DCM is often used in chemical synthesis and sample preparation due to its ability to dissolve a wide range of compounds and low boiling point. Researchers will need to:

• Identify safer alternative solvents where possible (see "Alternative Solvents" below).
• Update lab procedures to reflect proper handling requirements under the new rule.
• Ensure that ventilation, work practices, and personal protective equipment (PPE) meet the new safety standards.

Cleaning and Degreasing

Some labs use DCM for cleaning delicate lab equipment and removing grease or residue. Under the new rule:

• Labs must evaluate the possibility of switching to alternative cleaning agents (e.g., ethyl acetate, heptanes).
• Enhanced safety protocols, including proper ventilation and PPE, must be implemented if continued use is necessary.
• If the enhanced safety protocols are not sufficient to control DCM exposure, labs may need to establish regulated areas for any cleaning operations involving DCM.

To comply with the new EPA rule, UCSF EH&S requires the following steps:

 Chemical Inventory Update

• If your lab uses DCM, make sure it is listed in your chemical inventory.
• Check all biological kits or commercial products for DCM.

 Chemical Disposal

• If your lab has DCM that is no longer in use, submit a Chemical Waste Disposal Request through WASTe and remove it from your inventory.
• Non-research use of DCM (e.g., paint, paint strippers, aerosol sprays) is prohibited under the new rule.

 Exposure Monitoring and Training

• All labs continuing to use DCM must complete EH&S’s DCM Use Evaluation Survey by April 1, 2025.
• EH&S will conduct exposure monitoring and provide guidance on required PPE and handling procedures.
• Lab safety plans must be updated to reflect the new requirements, including a description of the use and handling of DCM. EH&S will provide guidance on how to accomplish this at a later date.

 Workplace Chemical Protection Program (WCPP)

• All labs using DCM must implement a WCPP to control exposure.
• EH&S will assist labs in developing and maintaining a compliant WCPP. Further guidance and templates will be available at a later date.

Researchers are encouraged to replace DCM with safer alternatives where possible.

Note: Other chlorinated solvents, such as 1,2-dichloroethane, are under EPA review and may face similar restrictions soon. Therefore, they should not be considered as alternatives.

If you plan to continue using DCM, you must follow the UCSF Workplace Chemical Protection Program (WCPP) to limit exposure. UCSF EH&S will assist labs with:

• Initial Monitoring – EH&S will monitor exposure levels and establish baseline data.
• Regulated Area Setup – If exposure monitoring of an area shows that airborne concentrations of DCM exceed exposure limits, that area must be marked off as a regulated area that is restricted-access. Per the EPA regulations, either a supplied-air respirator or self-contained breathing apparatus is required for entry into a regulated area. As such, establishment of regulated areas is considered an extreme last resort, only to be done for areas where other controls (such as fume hoods or work practice changes) are insufficient to control inhalation exposure.
• Exposure Control Plan – Labs must implement engineering controls, PPE use, and procedures to keep exposures below the 8-hour TWA and STEL limits.
• PPE Requirements – Researchers must use chemical-resistant gloves (e.g., polyvinyl alcohol or Silver Shield) and, if needed, respiratory protection. Double gloving with nitrile gloves may be acceptable when handling very small quantities of DCM or when chemical-resistant gloves are not practical, however gloves must be replaced immediately upon any incidental contact with DCM.
• Training – All staff must complete training before working with DCM. This training is expected to be delivered through the UC Learning Center and will be available at a later date.
• Periodic Monitoring – EH&S will conduct follow-up exposure monitoring based on risk levels:
  • If levels are below 1 ppm (TWA) and at or below 16 ppm (STEL), monitoring will occur every 5 years.
  • If levels are above 1 ppm (TWA) and/or above 16 ppm (STEL), monitoring will occur every 3 to 6 months, depending on the nature of the exceedance.*

* Periodic monitoring requirements are based on initial exposure monitoring results. See Table 1 of EPA 40 CFR Part 751 

If you have questions about the new DCM rule or need help adjusting your lab’s protocols, please contact:

• Exposure monitoring: [email protected]
• Chemical Hygiene Officer: [email protected]
• Campus research laboratories: Department Safety Advisor (DSA)
• UCSF Health: File a “Safety Assessment” MCSS ticket
• For all other areas: [email protected]