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1,1-Dichloroethene
Description: 1,1-Dichloroethene (C.A.S. 75-34-3) is primarily known as DCE and also as 1,1-dichloroethylene and vinylidene chloride. It is a man-made chemical that does not occur naturally. It is a clear, colorless liquid with a mild, sweet odor resembling that of chloroform. DCE is used to make plastic products such as flexible plastic food wrap and flame retardant fabrics, and in piping, coating for steel pipes, and adhesive applications. DCE is found in many food and other packaging materials. It is produced commercially by the dehydrochlorination of 1,1,2-tricholoroethane with excess lime or caustic. Chemical properties: Synonyms for DCE are 1,1-dichloroethylene; 1,1-DCE; 1,1,-dichloroethene asymdichloroethylene; ethene; 1,1-dichloro; ethylene; VDC; vinylidene chloride (inhibited); vinylidene chloride (II); vinylidene dichloride; ethylidene dichloride; and vinylidine chloride. DCE evaporates quickly at room temperature to form a vapor. A volatile organic compound, DCE also is quite volatile and flammable. It is released into the environment primarily as a result of air and water emissions coming from factories where DCE is manufactured, hazardous waste sites where DCE has been improperly disposed of, and as a result of accidental spills. DCE can also be found as a breakdown product of other chemicals present in the environment. It is not known how long DCE will persist in soil and water. Once in the air, the compound is rapidly decomposed through a variety of processes. It is estimated that DCE released into the atmosphere will persist for only about two days. The chemical is practically insoluble in water, and soluble in organic solvents. Identification: Health effects: The limited information available on the effects of inhaled DCE indicates that it can induce neurotoxicity after short-term exposure. Damage to the liver has been observed in humans following repeated exposure to DCE, presumably by inhalation. Central nervous system depression with accompanying symptoms of inebriation, which may progress to convulsions, spasms, and unconsciousness, have been observed in people acutely exposed to high concentrations of inhaled DCE. Complete recovery occurs if exposure is not prolonged. Human exposure to DCE is potentially highest in workplace settings and among populations residing in the vicinity of hazardous waste sites where the compound may contaminate environmental media. Although the presence of residua DCE in food wraps and other consumer products is another potential source of human exposure, there is no evidence to implicate consumer products as major sources of DCE exposure. Levels of DCE are significantly higher in areas surrounding production sites. Exposure Values: Economics: DCE is manufactured in chemical plants in Texas and Louisiana by Dow and by PPG Industries. Production capacity in 1985 was 178 million pounds per year, down from 270 million pounds in 1977. Estimated 1989 production is 165 to 175 million pounds. In 1988, plant capacity at PPG Industries was estimated at 64 million pounds. Regulation: The U.S. Food and Drug Administration (FDA) has issued proposed uses of vinyl chloride polymers; it deleted vinyl chloride-DCE copolymers from the list of materials that may be used on fruits. EPA offices overseeing regulations and guidelines for DCE are Air and Radiation (under the new Clean Air Act), Drinking Water, Water Regulations and Standards, Emergency and Remedial Response, Solid Waste, and Toxic Substances. Under Section 313 of the Emergency Planning and Community Right to Know Act of 1986, releases of more than one pound of 1,1-Dichloroethane into the air, water, and land must be reported annually and entered into the Toxic Release Inventory (TRI). Toxics Release Inventory Information 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:
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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 |