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Propylene Oxide
Description: Propylene oxide (C.A.S. 75-56-9) is a colorless liquid with an ether-like odor that is used mainly (60%) as a chemical intermediate in the production of polyurethane polyols, which are used to make polyurethane foams, coatings, and adhesives. It is used (20%) in the manufacture of propylene glycol, which is used in fiberglass-reinforced plastics, foods, cosmetics, pharmaceuticals, cigarette tobacco, packaging materials, dyes, and hydraulic fluids. It is also used in the preparation of glycol ethers (3%), dipropylene glycol (2%), industrial polyglycols, lubricants, surfactants, oil demulsifiers, isopropanolamines, and as a solvent and soil sterilant (6%). It is used in fumigation chambers for the sterilization of packaged foods; as a stabilizer for methylene chloride, fuel, and heating oils; in treating wood for termite resistance; as an acid scavenger and pH control agent; for removing residual catalysts from crude polyolefins; in fuel-air explosives in munitions; and as a component of Zeospan, a polyether rubber. Chemical properties: Propylene oxide is a volatile, flammable liquid that is soluble in water, alcohol, and ether. It is highly dangerous when exposed to heat or flame. It has a violent reaction with hydrogen chloride, chlorosulfonic acid, hydrogen fluoride, and oleum. It should not be stored in the presence of acids, bases, chlorides of iron, aluminum, and tin, or peroxides of iron and aluminum; any of these may cause violent polymerization. Propylene oxide is miscible with most organic solvents, and forms a two-layer system with water. It is incompatible with anhydrous metal chlorides, iron, strong acids, caustics, and peroxides, and reacts vigorously with oxidizing materials. When exposed to flame, propylene oxide will burn with a hot flame like isopropyl if not confined, but it may explode if confined. Polymerization may occur due to high temperatures or contamination with alkalis, aqueous acids, amines, and acidic alcohols. Synonyms for propylene oxide are epoxypropane; 1,2-epoxypropane; methyl ethylene oxide; methyl oxirane; propene oxide; and 1,2-propylene oxide. Derivatives of propylene oxide are polyether polyols; propylene glycol; di- and tripropylene glycol; poly (propylene glycol)s; surfactants; glycol ethers; and isopropanolamines. Identification: Health effects: Propylene oxide is classified as a substance which may reasonably be anticipated to be a carcinogen, according to the Sixth Annual Report on Carcinogens, published by the National Toxicology Program, U.S. Department of Health and Human Services. It is also classified as a carcinogen in EPA’s Toxic Release Inventory (TRI). If it is inhaled or ingested, or makes eye or skin contact, it can irritate the eyes, upper respiratory system, lungs, and skin. Exposure Values: Economics: U.S. manufacturers of propylene oxide are Dow Chemical Co, Midland, MI; Freeport, TX; and ARCO Chemical Co, Philadelphia; Bayport, TX. Regulation: The Occupational Safety and Health Administration (OSHA) issues permissible exposure limits for propylene oxide; that eight-hour time-weighted average (TWA) limit is 100 ppm. It also regulates propylene oxide under the Hazard Communication Standard and as a chemical hazard in laboratories. EPA regulates propylene oxide under the Clean Air Act, Clean Water Act, Comprehensive Environmental Response, Compensation, and Liability Act; Food, Drug, and Cosmetic Act; Resource Conservation and Recovery Act; and Toxic Substances Control Act. The Food and Drug Administration regulates propylene oxide as an indirect food additives in products which may come into contact with food and as an adjuvant for pesticide chemicals. Under Section 302 of the Emergency Planning and Community Right to Know Act of 1986, propylene oxide is listed as an Extremely Hazardous Substance and has a threshold planning quantity of 10,000 lbs. Under Section 313 of the Emergency Planning and Community Right to Know Act of 1986, releases of more than 100 lbs/24 hours of propylene oxide into the air, water, and land must be reported annually and entered into the Toxic Release Inventory (TRI). Facilities having a threshold quantity of 10,000lbs of propylene oxide are subject to the Risk Management Program Rule (RMP), Section 112r of the 1990 Clean Air Act with a toxic endpoint of 0.59 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 |