Methylene chloride, a colorless volatile liquid with a sweet aroma like chloroform, has long been an invaluable solvent across industries. Its ability to quickly dissolve a range of materials has made it a staple in paint thinners, adhesives, and laboratory work.
However, the same characteristics that make methylene chloride an effective solvent also come with major health risks. The chemical’s high vapor pressure means most exposures happen through air inhalation, making proper ventilation and safety protocols crucial in any workspace where it's used. We’ve also seen immediate effects on the central nervous system, decreased alertness, and potential long-term damage to vital organs.
This combination of widespread industrial use and serious health concerns has led the US Environmental Protection Agency (EPA) to implement new regulations under the Toxic Substances Control Act (TSCA). These regulations aim to balance the chemical's industrial use with the critical need to protect worker safety and public health.
Under the revised TSCA, the EPA has implemented new assessment requirements for managing occupational exposures from the commercial use of methylene chloride. These requirements differ substantially from those currently established by the Occupational Safety and Health Administration (OSHA):
Limited use: The chemical is now restricted to specific industrial activities, particularly affecting laboratory research and development (R&D) operations.
Workplace chemical protection program: New threshold limits have been established, including:
- Lower exposure limits.
- Action levels triggering controls.
- Short-term exposure limits.
Monitoring requirements:
- For private employers, initial monitoring must be completed by May 5, 2025.
- For federal agencies and contractors, initial monitoring must be completed on November 9, 2026.
- For new installations, assessment is required within 30 days.
- Labs with less than 30 days of annual exposure can use direct-reading instruments instead of traditional monitoring.
Exposure control plans:
- Private employers are required to prepare and implement by October 30, 2027.
- Federal agencies and contractors must prepare and implement by May 10, 2027.
- Required to document the entire hierarchy of controls.
- Personnel rotation is not allowed as a compliance method.
Respiratory protection:
- Must be implemented by August 1, 2025.
- Specific requirements based on exposure levels.
- Mandatory dermal protection for all handling.
TSCA requirements do not apply to substances regulated by the US Food and Drug Administration (FDA). However, whether chemical handling during drug discovery activities is considered an FDA-regulated activity is not yet entirely clear. There is an argument to be made that methylene chloride usage before the initial filing of an FDA drug application could be regulated under TSCA.
In the future, similar regulations are expected for similar solvents. In December 2024, the EPA issued new risk management guidelines for trichloroethylene (TCE) and perchloroethylene (PCE, more commonly known as PERC) in addition to carbon tetrachloride.
These regulations represent a significant shift in chemical safety management, with lower exposure limits and stricter controls than previous OSHA standards. While future administrations might affect the pace of new assessments, the fundamental approach to protecting worker safety is not going to change significantly.
Watch the webinar recording New requirements for methylene chloride exposure assessments to learn more about the new requirements.
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