Purpose and Applicability
Methylene chloride is used as a solvent in paint strippers, as a propellant in aerosols, in the manufacture of photographic film, and as a process solvent in the manufacturing of drugs. In the research laboratory it is commonly used for extractions. It is also used as a metal cleaning and finishing solvent. This generic chemical safety guidance describes basic prudent safety practice for handling this chemical in research labs. The principal investigator (PI) or the lab manager is responsible for developing and implementing standard operating procedures (SOPs) for the purchase, storage, and safe handling of this chemical that are specific to the PI’s research.
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Because methylene chloride is a volatile liquid, exposure can occur through inhalation. Exposure to methylene chloride may result in interference with the delivery of oxygen to tissues and central nervous system impairment depending upon its concentration in air. If you breathe methylene chloride at concentrations of 300 parts per million (ppm) or greater for a short period of time (3-4 hours) you may not be able to hear faint sounds and your vision may be slightly impaired. If you breathe in larger amounts (800 ppm) your ability to react fast, remain steady or perform tasks that require precise hand movements may be impaired. Additionally, prolonged exposures can produce headaches, irritability, dizziness, and nausea, tingling in the arms and legs, and numbness in the fingers and toes. In most cases, these effects will stop shortly after the exposure ends. The odor threshold varies from individual to individual, but concentrations of 200-300 ppm are usually easily detected by most persons. However, do not relay on your sense of smell to help you avoid unwanted exposures!
If not removed promptly, methylene chloride causes intense burning through direct skin contact and can cause corneal burns through direct eye contact. Prolonged skin contact may result in dermatitis. Inhalation of vapors may cause severe irritation of the respiratory system. Ingestion may cause nausea, vomiting, gastrointestinal irritation and burns to the mouth and throat. Methylene chloride is a poison and may be fatal if swallowed.
Closed containers exposed to heat may explode. Methylene chloride is incompatible with alkali metals, strong oxidizing agents, strong bases, and oxides of nitrogen, zinc, aluminum, water, magnesium, and amines.
Guidelines for Minimizing Worker Exposure
The National Institute for Occupational Health and Safety (NIOSH) and the Occupational Safety and Health Administration (OSHA) recommend that methylene chloride be regarded as a "potential occupational carcinogen" and that occupational exposures be controlled.
- Employ effective engineering controls, good work practices and proper maintenance procedures.
- Ideally, all work with methylene chloride should be conducted in a chemical fume hood (that has been tested by the EHS within the last 12 months) or in another type of appropriate exhaust ventilation. Using enclosed processes may also control exposure.
- Provide appropriate personal protective equipment (PPE) such as safety glasses with side shields, splash-proof goggles, and/or chemical-resistant aprons, coveralls, lab coats and gloves.
- Require that workers change any clothing that becomes contaminated with methylene chloride.
- Eating, drinking, smoking and the storage of food should be prohibited in areas where methylene chloride is stored or used.
- Exposures that cannot be controlled with ventilation or other work practices may require the use of a respirator.
- When possible, replace methylene chloride with a chemical that has been shown not to cause cancer or other adverse health effects in animals or humans.
- It is recommended that workers who are or who may be exposed to methylene chloride be given a copy of this fact sheet.
- Immediately and thoroughly wash with soap and water all areas of the body that come into contact with methylene chloride. Know the location and proper operation of safety showers in your immediate work area.
- Life threatening injuries should be treated as soon as possible at the nearest medical facility.
- For emergency injuries or illness use the UIHC Emergency Treatment Center. Inform them that the incident is work related.
- For other workplace injuries and illnesses use the UI HealthWorks (319-665-2111) which is located on Highway 965 in North Liberty.
- Methylene chloride waste is handled as a hazardous waste. Refer to EHS’ "Chemical Waste Disposal Guide" regarding the collection, storage, and disposal of hazardous wastes.
- Methylene chloride should be collected with other halogenated solvents, and should not be commingled with other types of hazardous waste.
The PI is responsible for SOPs specific to use of this chemical in their lab. The PI/Lab Manger is responsible for the site specific and hands-on training for the use of this chemical in their lab. Training should be directly documented in the researcher’s lab notebook. On each day of training, both trainer and trainee should sign the lab notebook.
Initially, researchers should perform the reactions with the PI or senior researcher present to observe the safe handling of this chemical. Review the reagent-specific safety data sheets (SDSs). Evaluate the hazards associated with the chemical reaction and experimental setup.