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Dichloromethane
Description: Dichloromethane (C.A.S. 75-09-2) is a clear, colorless liquid with a penetrating ether-like odor. It is used principally as a solvent in paint removers, as an aerosol propellant, and as a processing solvent in the manufacture of steroids, antibiotics, vitamins, and tablet coatings. It is also used as a degreasing agent, in electronics manufacturing, and as a urethane foam blowing agent. Dichloromethane is used in metal cleaning, as a solvent in the production of polycarbonate resins and triacetate fibers, in film processing, in ink formulations, and as an extraction solvent for spice oleoresins, caffeine, and hops. It is registered for use in the U.S. as an insecticide for commodity fumigation of strawberries, citrus fruits, and a variety of grains. Consumer products in which dichloromethane is used include spray shoe polish, water repellant/protectors, spot removers, wood floor and panel cleaners, contact cement, super glues, spray adhesives, adhesive removers, silicone lubricants, specialized electronic cleaners, wood stains, varnishes and finishes, paint thinners, aerosol spray paints, primers, aerosol rust removers, outdoor water repellants, glass frosting/artificial snow, spray lubricant for cars, transmission cleaners, battery terminal protectors, brake quieters/ cleaners, and gasket removers. Note that not all brands of a particular kind of product contain dichloromethane. Chemical properties: Dichloromethane is a nonflammable, volatile liquid that is slightly soluble in water, alcohols, phenols, aldehydes, ketones, and organic liquids. It is miscible with chlorinated solvents, diethyl ether, and ethanol. It will form an explosive mixture in an atmosphere with a high oxygen content, or in the presence of liquid oxygen, nitrite, potassium, or sodium. When heated to decomposition, it emitshighly toxic fumes of phosgene. Dichloromethane is incompatible or reactive with strong oxidizers; caustics, chemically-active metals such as aluminum, magnesium powders, potassium, and sodium; and concentrated nitric acid. Synonyms for dichloromethane are methylene chloride and methylene dichloride. Identification: Health effects: Dichloromethane is classified as a carcinogen in the Environmental Protection Agency's Toxic Release Inventory (TRI). It is also classified as a substance which may reasonably be anticipated to be a carcinogen in the Sixth Annual Report on Carcinogens, 1991, published by the National Toxicology Program, U.S. Department of Health and Human Services. The primary routes of potential human exposure to dichloromethane are inhalation and ingestion; exposure through the skin is a slower process. It affects the skin, eyes, central nervous system, and cardiovascular system. Short-term exposure to dichloromethane causes fatigue, weakness, sleepiness, light-headedness, numbness of limbs, tingling skin, nausea, and irritated skin and eyes. Exposure Values: Economics: U.S. manufacturers of dichloromethane are Dow Chemical USA, Freeport, TX; Hanlin Group, Inc, Moundsville, WV; Occidental Petroleum Corporation, Belle, WV; and Vulcan Materials Company, Geismar, LA, Wichita, KS. Regulation: EPA regulates dichloromethane under the Clean Air Act; Comprehensive Environmental Response, Compensation, and Liability Act (Superfund); Clean Water Act; Food, Drug and Cosmetic Act; Resource Conservation and Recovery Act; Superfund Amendments and Reauthorization Act; Safe Drinking Water Act; and Toxic Substances Control Act. The Consumer Product Safety Commission regulates household products containing dichloromethane, considering them to be hazardous and subjecting them to labeling requirements. The Occupational Safety and Health Administration (OSHA) has issued permissible exposure limits for dichloromethane, and regulates dichloromethane under the Hazard Communication Standard and as a chemical hazard in laboratories, 500 ppm TWA, 1,000 ppm CEILING, 2,000 ppm 5minute MAXIMUM PEAK IN ANY 2 HOURS. Under Section 313 of the Emergency Planning and Community Right to Know Act of 1986, releases of more than one pound of dichloromethane into the air, water, and land must be reported annually and entered into the Toxic Release Inventory (TRI). National Overview of 1998 Toxics Release Inventory See EPA's Toxic Release Inventory. Notations: The NIOSH recommended exposure limits (RELs) are time-weighted average (TWA) concentrations for up to a 10-hour workday during a 40-hour workweek. A short-term exposure limit (STEL) is designated by "ST" preceding the value; unless noted otherwise, the STEL is a 15-minute TWA exposure that should not be exceeded at any time during a workday. A ceiling REL is designated by "C" preceding the value. Any substance that NIOSH considers to be a potential occupational carcinogen is designated by the notation "Ca." The OSHA permissible exposure limits (PEL) are found in Tables Z-1, Z-2, and Z-3 of the OSHA General Industry Air Contaminants Standard (29 CFR 1910.1000). Unless noted otherwise, PEL are TWA concentrations that must not be exceeded during any 8-hour workshift of a 40-hour workweek. A STEL is designated by "ST" preceding the value and is measured over a 15-minute period unless noted otherwise. OSHA ceiling concentrations (designated by "C" preceding the value) must not be exceeded during any part of the workday; if instantaneous monitoring is not feasible, the ceiling must be assessed as a 15-minute TWA exposure. In addition, there are a number of substances from Table Z-2 (e.g., beryllium, ethylene dibromide, etc.) that have PEL ceiling values that must not be exceeded except for specified excursions. For example, a "5-minute maximum peak in any 2 hours" means that a 5-minute exposure above the ceiling value, but never above the maximum peak, is allowed in any 2 hours during an 8-hour workday. Information Sources:
Originally published in Environment Writer by the National Safety Council. Reprinted with permission. Environment Writer Metcalf Institute for Marine and Environmental Reporting University of Rhode Island Graduate School of Oceanography Office of Marine Programs Narragansett, RI 02882 Tel: 401-874-6211; Fax: 401-874-6485 Disclaimer * Copyright 2002-2006 * All rights reserved. * University of Rhode Island |