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OCCUPATIONALSAF 4SBESTOS This guideline summarizes pertinent information about as- bestos for workers, employers, and occupational safety and health professionals who may need such information to con- duct effective occupational safety and health programs. Recomr- mendations may be superseded by new developments in these fields; therefore, readers are advised to regard these recom- mendations as general guidelines. Data in the following section are presented for various forms of asbestos: (1) Asbestos (mixed forms); (2) Chrysotile; (3) Amosite; (4) Crocidolite; (5) Tremolite; (6) Anthophyllite; (7) Actinolite. If unspecified, data apply to all forms. • Composition: (1) Not Available; (2) 3MgO-2SiO2-2H2O; (3) (FeMg)SiO3; (4) NaFe(SiO3)2-FeSiO3-H20; (5) Ca2Mg%Si9022(OH)2; (6) (MgFe)-1Si8022(OH)2; (7) Cao-3(MgFe)0-4SiO2 • Synonyms: (1) Asbestos fiber, serpentine, amphibole; (2) Canadian chrysotile, white asbestos, serpentine; (3) Brown asbestos, fibrous grunerite; (4) Blue asbestos; (5) Fibrous tremolite; (6) Azbolen asbestos; (7) Not available • Identifiers: (1) CAS 1332-21-4; RTECS CI6475000; DOT 2212 (blue) 2590 (white); (2) CAS 12001-29-5; RTECS CI6478500; DOT 2590; (3) CAS 12172-7375; RTECS CI6477000; DOT Not assigned; (4) CAS 12001-28-4, RTECS C16479000; DOT 2212; (5) CAS 1456773-8; RTECS C16560000; DOT Not assigned; (6). CAS 1706878-9; RTECS CI6478000; DOR' Not assigned; (7) CAS 13768-00-8; RTECS CI6476000; DOT Not assigned • Appearance and odor: A fiber or filament, asbestos may have a "fluffy„ appearance. Colors may vary from white, gray, blue, brown, green or yellow. Positive identification requires microscopic examination. • • Physical data 1. Molecular weight: (2) 277.13; (5) 185.03 2. Specific gravity (water = 1): 2.5-3.0 3. Noncombustible solid • Warning properties Evaluation of warning properties for respirator selection: Warring properties are not considered in reconuncrrding respi- rators for use with carcinogens. EXPOSURE LIMITS Only asbestos fibers greater than 5 micrometers OA)m in length are considered for the following exposure limits. The current Occupational Safety and Health Administration (OSHA) per- missible exposure limit (PEL) for asbestos is 0.2 fiber per cu- bic centimeter (cc) of air as a time -weighted average (TWA) concentration over an 8 -hour workshift with an action level of 0.1 fiber/ac as an hour TWA. The National Institute for Oc- cupational Safety and Health (NIOSH) recommends that as- bestos be controlled and handled as a potential human carcinogen in the workplace and that exposure be minimized to the lowest feasible limit. The NIOSH recommended ex- posure xposure limit (REL) is 0.1 fiber/cc (in 40 -liter air sample) as a TWA concentration for up to an 8 -hour workshift, 40 -hour workweek. The American Conference of Gommmental Indus- trial Hygienists (ACGIR) has designated asbestos as an Al sub- stance (suspected human carcinogen, with an assigned threshold limit value/ TLV 9) of 2 fibers/cc for chrysotile, 0.5 fiber/cc for amosite, 0.2 fiber/cc for crocidolite, and 2 fibers/cc for other forms, as a TWA for a normal 8 -hour workday and a 40 -hour workweek (Table 1). U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service Centers for Disease Control National Institute for Occupational Safety and Health ransfer Division of Standards Development and Technology T