ethyl groups on alternate sides of plane of carbon atom chain); and atactic or not fiber-forming (methyl groups in a random arrangement with respect to plane of carbon atom chain). The isotactic form is practically insoluble in cold organic solvents; it is used for fishing gear, ropes, filter cloths, laundry bags, protective clothing, blankets, fabrics, carpets, yarns, etc. It is also used in injection molding for auto parts and in bottle caps, and for container closures (4:1307-8; 3). Lewis reports that polypropylene is a "questionable carcinogen. When heated to decomposition it emits acrid smoke and irritating fumes" (3:2904).
Pinkerton, Kociba, Petrella, McAllister, Willis, Fulfs, Thoma, and Hutzinger investigated toxicity of polystyrene combustion with and without flame retardants. Dermal route of exposure in rabbits was chosen to simulate one of the principal routes that human exposure to soot or char might occur; rabbit ear bioassay for comedogenic activity was used due to its historically documented acceptance and usefulness for detection of the presence or absence of materials such as halogenated dioxins and furans possessing comedogenic and oth
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