Working Safely with Methylene Chloride�(Dichloromethane)

ENVIRONMENTAL, HEALTH, SAFETY, AND

RISK MANAGEMENT

UNIVERSITY OF ALASKA FAIRBANKS

October 2022

Overview

• Properties of Methylene Chloride
• Exposure Limits
• Health Effects
• Routes of Exposure
• Protecting Yourself
• Handling and Storage
• Spills and Exposures
• Waste Disposal
• Methylene Chloride Spill Procedures

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Properties of Methylene Chloride

• Also called MC, Dichloromethane, DCM, CH₂Cl₂
• Liquid: clear and colorless, with a chloroform-like odor (pleasant, sweet)
• High vapor pressure—readily evaporates
• Odor threshold varies from 25 ppm – 300 ppm
• PEL is 25 ppm.
• So if you smell it, you’re already over exposed
• Vapor Density = 2.9 (air = 1)
• Much heavier than air, will sink

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Exposure Limits

OSHA Methylene Chloride Standard (it’s the law!)

• 29 CFR 1910.1052 Establishes the following:
• 8-hour Permissible Exposure Level (PEL) at 25 ppm (parts per million)
• 15 min Short-Term Exposure Level (STEL) at 125 ppm
• Action level at 12.5 ppm (8 hours)
• At this exposure level, employee must undergo medical surveillance
• Specifies requirements for PPE (personal protective equipment), air monitoring, establishment of regulated areas, etc.

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Health Effects—Acute

Acute health effects

Short-term effects

Show up immediately/shortly after exposure

• Central nervous system depressant
• Adverse effects on heart due to production of CO during metabolism of methylene chloride
• Evidence for liver toxicity (elevated liver enzymes)
• Immediate symptoms may include:
• Dizziness
• Headaches
• Irritation of eyes, respiratory tract, skin, mucous membranes
• Loss of coordination (leading to accidents and mistakes)
• Narcosis (at high exposures)

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Health Effects—Chronic

Chronic health effects

Long term health effects

Caused by regular exposure over a long period of time.

These effects are usually permanent.

• Clear evidence exists this causes cancer in animals
• Studies suggest that there is an increased risk of cancer among workers who are exposed to methylene chloride
• Other studies show no apparent correlation
• NIOSH (National Institute for Occupational Safety and Health)/CDC (Center for Disease Control) recommends regulation as a suspect carcinogen (lung and liver cancer).

https://www.atsdr.cdc.gov/toxfaqs/tfacts14.pdf

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Routes of Exposure

• Inhalation
• Primary route of exposure due to high volatility
• Skin absorption
• Occurs via contact with liquid and/or vapor
• Eyes
• Splashes with liquid, or exposure to vapors
• Ingestion (rare)
• Eating or drinking without washing hands and face after working with methylene chloride

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Routes of Exposure: Inhalation

• Methylene chloride is primarily an inhalation hazard
• At high levels, may cause nausea, vomiting, light-headedness, numbness to extremities, unconsciousness and even death
• May cause irritation to respiratory tract
• Methylene chloride is metabolized to carbon monoxide (and carbon dioxide) in the body
• Prolonged exposure may lead to liver damage and cancer

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Routes of Exposure: Skin, Eyes

• Skin exposure may cause irritation or burns
• Removes natural oils from skin
• Readily absorbed through the skin
• Contributes to exposure by inhalation when absorbed through skin
• Vapors cause pain and irritation to eye
• Splashes may cause severe irritation and possible eye damage

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Exposure by Ingestion is rare

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Protecting Yourself

• Engineering controls
• Personal protective equipment
• Specific lab safety practices

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Protecting Yourself: Engineering Controls

• Use all methylene chloride-containing solutions in a properly functioning chemical fume hood
• Make sure the fume hood has a current maximum sash height sticker (tested by EHSRM within the last year)
• Conduct all work at least 6” inside sash
• Keep sash as low as possible (even lower than the posted maximum operating sash height)
• Conduct all work in a plastic tray for spill containment
• Keep all bottles closed when not in immediate use

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Protecting Yourself: �Personal Protective Equipment (PPE)

• Long pants and long-sleeve shirt with reasonably high neck (no low cut shirts)
• Closed-toe shoes or rubber boots
• Chemical resistant lab coat (NOT the standard cotton-poly ones) or chemical resistant apron
• Splash goggles (in addition to fume hood sash)
• Gloves: Polyvinyl alcohol (PVA) or laminate barrier (Silver Shield^®)
• DO NOT USE NITRILE, NEOPRENE OR LATEX!
• Additional PPE may be required, depending on the specific procedures used in your lab

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Specific Lab Safety Practices

• Review your protocol prior to beginning the procedure (every time)
• Inspect your PPE for cracks, holes, signs of wear
• Clearly label ALL bottles (stocks and wastes)
• Use the smallest amount possible
• Have a copy of the SDS in the lab Chemical Hygiene Plan notebook
• Ensure that there is unobstructed access to a functioning emergency eyewash and shower
• Check emergency equipment to make sure that it has been tested on a regular (weekly) basis

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Storage and Handling

• Classified as a health hazard (color coded blue)
• Use secondary containment (polyethylene tray) for all bottles (stocks and wastes)
• Ensure that caps are tightly sealed
• If you are losing volume in your bottles over time, then you effectively have a release to the environment (a.k.a. a spill)
• Check bottles regularly
• Store in a well-ventilated area

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Spills and Exposures

• Spills not involving contact with a person
• If you do not feel comfortable cleaning up the spill, call EHSRM for help (never put yourself at risk!)
• Always wear your PPE when cleaning up a spill
• Small spill (e.g. a few mL):
• Use absorbent pads to mop up the liquid
• Place all pads and towels in a double plastic bag and seal. Leave in the hood
• Notify EHSRM (907-474-5617)
• Large spill (e.g. 1 L or more)
• Alert others in the area to evacuate the lab
• Call EHSRM at 907-474-5617 or 907-474-5413

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Spills and Exposures: Skin/Eye

Spills involving skin/eye exposure

• Immediately wash the affected areas with running water (at least 15 minutes).
• If large areas of the body are involved, immediately get to the emergency shower or eyewash (if eye exposure only)
• Remain in the shower for 15 minutes, removing all clothing and contaminated items while in the shower
• Be alert for signs and symptoms of exposure—dizziness, headache, confusion
• Skin exposures WILL cause inhalation exposure as well
• Immediately notify EHSRM (907-474-5413), and your supervisor of the incident. Seek medical attention.

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Spills and Exposures: Ingestion/Inhalation

• If swallowed, DO NOT INDUCE VOMITING. Give large quantities of water. Never give anything by mouth to an unconscious person. Get medical attention immediately.
• If inhaled, victim should be moved to fresh air if it is safe to do so. Get medical attention immediately.

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To Avoid Spills/Exposures, Plan Ahead

• Anticipate steps in your process where something could go wrong, and plan for them.
• Example: You are centrifuging samples containing methylene chloride and one of the tubes breaks in the rotor.
• What do you do? What is the hazard here?
• Example: You are working with methylene chloride and the fire alarm goes off.
• What do you need to do to secure your experiment before evacuating the building?

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Waste Disposal

• Collect all methylene chloride-containing wastes in a well-labeled compatible (glass or PTFE—Teflon®) container
• No methylene chloride (no matter how dilute) should be put down the drain
• Clearly label container with the concentration of methylene chloride, and a warning statement (e.g. “health hazard: toxic”)
• When the container is full, complete online Hazardous Waste Pickup Request. Don’t know how? Contact EHSRM at 474-5197 or visit the EHSRM Website:

www.uaf.edu/safety

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Questions?

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• Questions? Need Assistance? Contact EHSRM
• 907-474-6771 or 907-474-5617
• Emergency, call: 911
• Dispatch (Fire & Police): 907-474-7721
• Facilities Services: 907-474-7000

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