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Chloromethane
Description: Chloromethane (C.A.S. 74-87-3) is a clear, colorless gas also known as methyl chloride. It occurs in the natural environment and is present in air at very low levels. It is used to make other substances, primarily silicones, and to make agricultural chemicals, methyl cellulose, quaternary amines, and butyl rubber. It had been used as a refrigerant, but is no longer used because of its toxic effects. Refrigerators more than 30 years old may contain chloromethane and may be a source of high-level exposure. Chloromethane has also been used as a foam-blowing agent, pesticide, and fumigant. Chloromethane is found as a pollutant in municipal waste streams from treatment plants, as well as industrial waste streams. Some manufacturing processes for vinyl chloride also result in chloromethane as an impurity in the vinyl chloride end product. Chemical properties: Chloromethane has a faint, sweet odor that is noticeable only at levels that may be toxic. It is heavier than air and is extremely flammable. It is soluble in water, benzene, carbon tetrachloride, glacial acetic acid, and absolute alcohol. It reacts with ammonia to form methyl amine hydrochlorides, and slowly decomposes in the presence of water to become corrosive to metals. It reacts explosively with lithium, sodium, potassium, and magnesium. Spontaneously flammable aluminum trimethyl is formed upon reaction of chloromethane with aluminum in the presence of trace aluminum chloride. Synonyms for chloromethane are methyl chloride; monochloromethane; artic; chlorure de methyle (DOT French); cloruro de metilo (DOT Spanish); gas refrigerante R-40 (DOT Spanish); gaz refrigerant R-40 (DOT French); HCC 40; methane, chloro-; R 40; R 40 (refrigerant); RCRA Waste Number U045; refrigerant gas R-40; and UN 1063. Identification: Health effects: Exposure to high levels of chloromethane can cause convulsions, coma, and death. The central nervous system is the major target of chloromethane toxicity. Exposure at lower levels can cause staggering, blurred or double vision, dizziness, fatigue, personality changes, confusion, tremors, muscle cramping, headache, uncoordinated movements, nausea, vomiting, and jaundice. Exposure can harm the liver and kidneys and affect the heart rate and blood pressure. People who have kidney or liver disease, anemia, or neurological deficits may be more susceptible to the toxic effects of chloromethane. Exposure Values: Economics: U.S. manufacturers of chloromethane Dow Chemical USA, Freeport, TX; Dow Corning Corp, Carrollton, KY; General Electric Co, Mount Vernon, IN; Hanlin Group, Inc, Moundsville, WV; Union Carbide Corporation, South Charleston, WV; Vista Chemical Co, Lake Charles, LA; Occidental Chemical Corp, Dallas, TX; and Vulcan Materials Co, Birmingham, AL. Regulation: The Occupational Safety and Health Administration (OSHA) issues permissible exposure limits for chloromethane. The EPA Offices of Air and Radiation, Drinking Water, Emergency and Remedial Response, Solid Waste, and Prevention, Pesticides, and Toxic Substances regulate chloromethane. Chloromethane is regulated under the Emergency Planning and Community Right-to-Know Act; Clean Air Act; Comprehensive Environmental Response, Compensation, and Liability Act (Superfund); Clean Water Act, on the Priority Pollutant List; and Resource Conservation and Recovery Act. OSHA lists chloromethane as a Highly Hazardous Chemical under the Process Safety Management Standard at a threshold quantity of 15,000 pounds. Under Section 313 of the Emergency Planning and Community Right to Know Act of 1986, releases of more than one pound of chloromethane into the air, water, and land must be reported annually and entered into the Toxic Release Inventory (TRI). Facilities having a threshold quantity of 10,000 lbs of chloromethane are subject to the Risk Management Program Rule (RMP), Section 112r of the 1990 amendments to the Clean Air Act. Chloromethane has a toxic endpoint of 0.82 mg/L. 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 |