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3,3'-Dichlorobenzidine
Description: 3,3'-Dichlorobenzidine (C.A.S. 91-94-1) is a gray to purple crystalline solid which does not occur naturally and has a mild odor. It is produced through the alkaline reduction of o- nitrochlorobenzidine with subsequent rearrangement in the presence of acid. 3,3'-Dichlorobenzidine is manufactured for use in the production of yellow, and some red and orange, pigments for the printing ink, textile, paper, paint, rubber, leather, plastic, and related industries. It is also used as a compounding ingredient for rubber and plastics, and can be used to test for the presence of gold. It is used in the formulation of the raw material tetraminobiphenyl which is used to produce polybenzimidazole (PBI), used in many protective clothing applications, such as firefighters' apparel, welders' garments, high temperature gloves, and crash rescue garments. Chemical properties: 3,3'-Dichlorobenzidine does not evaporate; it is unstable in water exposed to natural sunlight and in air, but remains in soil for months. The estimated half- life in air ranges from 1 to 60 days. In water exposed to natural sunlight, it is expected to degrade rapidly with a half- life of approximately 90 seconds. It is soluble in alcohol and benzene. EPA has classified 3,3'-dichlorobenzidine as a volatile organic compound, an air toxic under the new Clean Air Act, and a de minimis carcinogen. Synonyms for 3,3'-dichlorobenzidine are: 3,3'-dichloro-4,4'- diaminobiphenyl; 4,4'-diamino-3,3'-dichlorobiphenyl; and o,o'- dichlorobenzidine. Identification: Health effects: 3,3'-Dichlorobenzidine is classified by the U.S. Occupational Safety and Health Administration (OSHA) as a "de minimis" carcinogen, meaning that the minimum amount of the chemical set by OSHA is considered to be carcinogenic. It is listed in EPA's Toxic Release Inventory (TRI) as a de minimis carcinogen. Workers exposed to the salt form of the chemical complained of sore throats, respiratory infections, and upset stomachs, but studies were not conclusive about those effects. Dermatitis was also cited by workers in contact with it. The greatest occupational health risks exist in the processing of 3,3'-dichlorbenzidine in the synthesis of azo dyes, and for workers in the garment, leather, printing, paper, and homecraft industries where benzidine-based dyes are used. Exposure Values: Economics: U.S. manufacturer of 3,3'-dichlorobenzidine is Wall Chemical Corp, Westfield, NJ. Regulation: OSHA has established permissible exposure limits for 3,3'-dichlorobenzidine in the air, and has classified it as a carcinogen. Offices within EPA responsible for regulations applicable to the chemical are Water Regulations and Standards, Emergency and Remedial Response, and Solid Waste. Under Section 313 of the Emergency Planning and Community Right to Know Act of 1986, releases of more than one pound of 3,3'- dichlorobenzidine 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 |