 |
Also see:
|
Bromomethane
Description: Bromomethane (C.A.S. 74-83-9), also commonly known as methyl bromide, is a colorless, almost odorless gas; it has a chloroform-like odor at high concentrations. Some bromomethane is formed in the ocean, probably by algae or kelp. Most bromomethane is made by humans to be used as a soil or space fumigant for the control of rats, insects, and fungi; some is used to make other chemicals. It is also used as a methylating agent in various chemical reactions, and as a solvent to extract oils from nuts, seeds, and wool. It is usually stored in sealed containers to keep it from evaporating. Bromomethane was used in fire extinguishers in Europe from the 1920s to the 1940s, but never gained widespread use as a fire extinguishing agent in the United States. Chemical properties: Bromomethane is incompatible or reactive with aluminum, magnesium, and strong oxidizers. It attacks aluminum to form aluminum trimethyl, which is spontaneously flammable. It is freely soluble in organic solvents and is nonflammable on its own. Its fire hazard is moderate when exposed to heat or flame; its explosion hazard is moderate when exposed to sparks or flame. When heated to decomposition, bromomethane emits highly toxic fumes of bromides. Bromomethane is shipped as a liquefied compressed gas. It breaks down in the environment to other chemicals. In air, it takes about 11 months for half of the bromomethane released to disappear; in underground water, it takes about one month for half of the chemical to break down. Synonyms for bromomethane are methyl bromide, monobromomethane, and methyl fume. Identification: Health effects: Death following acute poisoning by bromomethane is usually caused by its irritating effect on the lungs. In chronic poisoning, death is due to injury to the central nervous system. Breathing bromomethane can cause headaches, weakness, confusion, numbness, visual disturbances, vomiting, lack of coordination, convulsions, and nausea. Breathing large amounts may cause fluid to build up in the lungs, resulting in difficult breathing; it may also cause muscle tremors, ataxia, paralysis, coma, and seizures. Kidneys may be injured, and urine production may slow or stop. In severe cases, these effects can lead to death. The lung may be severely injured by inhalation exposure to bromomethane; edema is a common effect, often accompanied by focal hemorrhagic lesions. High levels of exposure to bromomethane vapor can result in adverse renal effects, including congestion, anuria or oliguria, and proteinuria. Bromomethane vapor can also cause conjunctivitis, erythema, rashes, or blisters. Skin contact with bromomethane can cause severe burns, itching, redness, and blisters. Because bromomethane has very little odor at potentially toxic levels, and because effects on the body are generally delayed, people may be exposed to hazardous levels without being aware that the exposure is occurring. The general population is not likely to be exposed to high levels of bromomethane except in the immediate vicinity of industrial facilities that release the gas into air, or near locations where it is being used as a soil or a space fumigant. Bromomethane is classified as a carcinogen, according to the National Institute for Occupational Safety and Health's "Pocket Guide to Chemical Hazards"; it is not classified as a carcinogen by either the U.S. Department of Health and Human Services, or the U.S. Environmental Protection Agency. Exposure Values: Economics: U.S. manufacturers of bromomethane are Ethyl Corp. Richmond, VA, Chemicals Group Baton Rouge, LA, Great Lakes Chemical Corp. West Lafayette, IN. Regulation: EPA offices regulating bromomethane in water are Drinking Water, and Water Regulations and Standards; regulating bromomethane in food is Pesticide Products; other offices regulating bromomethane are Emergency and Remedial Response, Solid Waste, and Toxic Substances. The Food and Drug Administration has issued tolerances of inorganic bromide in processed food as a result of fumigation with methyl bromide, and tolerances for residues of inorganic bromide from fumigation with methyl bromide on cereal grains and processed grains used in production of fermented malt beverages. Under Section 302 of the Emergency Planning and Community Right to Know Act of 1986 , bromomethane is listed as an Extremely Hazardous Substance and has a threshold planning quantity of 1000 lbs. Under the Emergency Planning and Community Right-to-Know Act of 1986, releases of more than one pound of bromomethane into the air, water, or 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 |