Introduction

The US EPA evaluated the environmental and human health risks of methylene chloride (dichloromethane) as required by the revised Toxic Substances Control Act. In compliance with congressional mandates, they identified health risks to workers and consumers who use methylene chloride-containing productsⁱ, as well as bystanders in workplaces and residences where methylene chloride is used. 

Health Effects

Effects of short-term (acute) exposures to workers and consumers, including bystanders, can result in harm to the central nervous system (neurotoxicity). Effects of longer periods of exposure (chronic) for workers includes liver toxicity, liver cancer, and lung cancer.

Regulatory Protections and Scope of Use

The methylene chloride rule specifies that industrial and commercial use of methylene chloride as a laboratory chemical will continue with strict protections under the Workplace Chemical Protection Program (WCPP). This includes the use of methylene chloride in a laboratory process or in specialized laboratory equipment for instrument calibration and maintenance, chemical analysis, chemical synthesis, extracting and purifying other chemicals, dissolving other substances, executing research, development, test and evaluation methods, and similar activities, such as use as a solvent, reagent, analytical standard, or other experimental use. This also includes the use of methylene chloride in EPA analytical methods.  

This applies to research, government, and academic institutions, as well as to industrial and commercial laboratories. Laboratory use of methylene chloride includes Department of Defense sampling, examining, and testing of solid propellants, detail specifications of nitrocellulose, and laboratory analysis for TNT conformity with TNT acidity requirements.

Use of methylene chloride in the lab, regardless of scale or volume, is regulated by the WCPP. The WCPP includes two occupational exposure limits to address unreasonable risk from methylene chloride, and ancillary requirements to support those limits, including initial and periodic monitoring, a requirement to reduce exposures to the extent feasible according to the NIOSH hierarchy of controls, and PPE guidance to address remaining risks above the occupational exposure limits.

Allowed Conditions of Use

Allowed condition of use of Methylene Chloride includes industrial and commercial use as a laboratory chemical (Table 1, pg 6 in reference)ⁱⁱ.

Workplace Chemical Protection Program

Requirements and Deadlines

The US Environmental Protection Agency’s new rule established specific requirements and deadlines using the Workplace Chemical Protection Program (WCPP):

Exposure Limits (Use as a Laboratory Chemical)

The WCPP requirements include inhalation exposure limits, called the EPA existing chemical exposure limit (ECEL), and EPA short term exposure limit (EPA STEL), to protect potentially exposed persons. Provisions include:

Regulated Area(s)

Any person who owns, leases, operates, controls, or supervises a workplace must mark areas where airborne concentrations of methylene chloride exceed, or there is a reasonable possibility they may exceed the inhalation exposure limits, the applicable ECEL or EPA STEL.

Potentially Exposed Person(s)

Any person who may be exposed to a chemical substance (in this case methylene chloride) in a workplace because of a condition of use of that chemical substance or mixture falls within the scope of the exposure regulations. This includes workers, employees, independent contractors, employers, and all other persons in the workplace where methylene chloride is present.  

What about OSHA Requirements?

Laboratories that are required to follow the OSHA chemical-specific methylene chloride standard 29 CFR 1910.1052^iv  (8CCR5202^v) and the OSHA laboratory standard^vi continue to be subject to these regulations. The EPA’s methylene chloride rule does not modify those requirements. The EPA has confidence that a properly designed and functioning fume hood are key measures to mitigate occupational exposure to methylene chloride in laboratories. The measures in the WCPP will address the unreasonable risk identified by EPA from methylene chloride laboratory use. Owners and operators of laboratories must conduct initial monitoring to demonstrate the extent to which fume hoods mitigate exposure to methylene chloride, and follow appropriate periodic monitoring based on that result. This monitoring could occur as infrequently as every 5 years if monitoring is below the action level. An institution’s existing Chemical Hygiene Plan may need to be augmented to include the details needed for the methylene chloride WCPP exposure control plan. If it is not feasible to mitigate occupational exposure below the ECEL value through exposure controls and work practices, laboratories must consider personal protective equipment such as respiratory protection to mitigate worker exposure to methylene chloride.

For new facilities, labs must conduct exposure monitoring within 30 days of initial use and limit exposure to the ECEL and EPA STEL within 90 days of initial monitoring.

ⁱ There are uses of methylene chloride which are exempt (pg. 10, III: C. of https://www.epa.gov/system/files/documents/2024-07/mecl-compliance-guide.pdf)
ⁱⁱ Ibid.
ⁱⁱⁱ https://www.acgih.org/dichloromethane-2/
^iv https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1052
^v https://www.dir.ca.gov/title8/5202.html
^vi https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1450

Author

Russ Vernon, Ph.D.
EH&S Business Development Manager
Risk and Safety Solutions