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1,4-Dichlorobenzene
Description: The compound 1,4-dichlorobenzene (C.A.S. 106-46-7) is most commonly referred to as para-DCB or p-DCB. It is widely used as a moth killer, in space deodorizers, and in the production of polyphenylene sulfide. It is also used in the manufacture of certain resins, in the pharmaceutical industry, and as a general insecticide in farming. Chemical properties: Synonyms for 1,4-dichlorobenzene are 1,4-dichlorobenzene; 1,4-dichlor-B; 1,4-Diclorobenzene; benzene, 1,4-dichloro; benzene, p-dichloro; dichlorobenzene, para, solid; p-chlorophenyl chloride; p-DCB; p-dichloorbenzene; p- dichlorbenzol; p-dichlorobenzene; p-dichlorobenzol; p- diclorobenzene; parazene; PDB; para-DCB; paradichlorobenzene; and paradichlorobenzol. At room temperature, 1,4-dichlorobenzene is a white or colorless crystalline solid with a characteristic penetrating odor. When exposed to air, it is slowly transformed from its solid state into a vapor; the released vapor then acts as a deodorizer and insect killer. It is practically insoluble in water and is soluble in alcohol, acetone, ether, chloroform, carbon disulfide, and benzene. Identification: Health effects: There is limited evidence that 1,4- dichlorobenzene can damage a developing fetus. Exposure can damage the lungs, liver, kidneys, and blood cells, causing anemia; it can also cause swelling of the eyes, hand, and feet. It can damage the nervous system, causing weakness, trembling, and numbness in the arms and legs. It may cause a skin allergy, which when developed, can cause itching and a skin rash. Higher levels of the chemical in air, such as the levels that are sometimes associated with industrial exposure, can cause headaches, nausea, clumsiness, slurred speech, and dizziness. Levels that would result in death would be associated with an odor so intense that it would be very unpleasant, if not intolerable, and would serve as a danger warning. In industrial situations, workers exposed to 1,4-dichlorobenzene at high levels are usually directed to wear respirators. Workers involved in the production of the chemical may be exposed to concentrations significantly higher than those encountered by the general population. High exposure levels may result from some consumer of moth repellents and room deodorizers. Approximately 95 percent of the environmental releases of 1,4-dichlorobenzene occurs during its use, rather than during its manufacture or processing. Exposure Values: Economics: U.S. manufacturers of 1,4- dichlorobenzene are Monsanto Chemical Co, Sauget IL ; Chemicals Group, New Martinsville, WV; Governor Lea Road, Delaware City, DE; Regulation: The Occupational Safety and Health Administration issues permissible exposure limits in workplace air for 1,4-dichlorobenzene. EPA offices overseeing regulations and guidelines applicable to 1,4-dichlorobenzene are Drinking Water, Emergency and Remedial Response, Solid Waste, Toxic Substances, and Pesticide Programs. Under Section 313 of the Emergency Planning and Community Right to Know Act of 1986, releases of more than one pound of 1,4- dichlorobenzene 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 |