Title: Polychlorinated Biphenyls
Additional Names: PCBs; chlorinated biphenyls; chlorobiphenyls
Trademarks: Aroclor (Monsanto); Clophen (Bayer); Fenclor (Caffaro); Kanechlor (Kanegafuchi); Pyralene (Prodelec)
Literature References: Once widely used industrial chemicals whose high stability contributed to both their commercial usefulness and their long-term deleterious environmental and health effects. Synthesis: H. Schmidt, G. Schulz, Ann. 207, 338 (1881). Commercially available since 1930: C. Penning, Ind. Eng. Chem. 22, 1180 (1930). Commercial PCBs are mixtures of various isomers and congeners. The Aroclors are characterized by four digit numbers. The first two digits indicate that the mixture contains biphenyls (12), triphenyls (54) or both (25, 44); the last two digits give the weight percent of chlorine in the mixture (e.g. Aroclor 1242 contains biphenyls with ~42% chlorine). Accumulation of airborne PCBs in foliage: E. H. Buckley, Science 216, 520 (1982). Reviews: H. L. Hubbard in Kirk-Othmer Encyclopedia of Chemical Technology vol. 5 (Interscience, New York, 2nd ed., 1964) pp 289-297; O. Hutzinger et al., The Chemistry of PCBs (CRC Press, Cleveland, Ohio, 1974) 269 pp; J. W. Lloyd et al., J. Occup. Med. 18, 109-113 (1976). Reviews of environmental impact and toxicity: L. Fishbein, Annu. Rev. Pharmacol. 14, 139-156 (1974); National Conference on Polychlorinated Biphenyls, Nov. 19-21, 1975 (EPA-560/6-75-004, 1976) 487 pp; R. D. Kimbrough, Crit. Rev. Toxicol. 2, 445-498 (1974); S. H. Safe, ibid. 24, 87-149 (1994). Reviews of carcinogenicity: IARC Monographs 18, 43-103 (1978); E. M. Silberhorn et al., Crit. Rev. Toxicol. 20, 439-496 (1990); of toxicology and mechanism of action: S. Safe, ibid. 13, 319-395 (1984); of toxicology and human exposure: Toxicological Profile for Polychlorinated Biphenyls (PB2000-108027, 2000) 948 pp.
Derivative Type: Aroclor 1242
Properties: Clear, mobile liquid; av. number Cl/molecule: 3.10. d425 1.381, d415.5 1.392. Distillation range 325-366°. Flash point (open cup) 348-356°F. nD20 1.627-1.629. Dielectric constant (1000 cycles) 5.6 (25°), 4.9 (100°).
Flash point: Flash point (open cup) 348-356°F
Index of refraction: nD20 1.627-1.629
Density: d425 1.381; d415.5 1.392
Derivative Type: Aroclor 1254
Properties: Light yellow, viscous liquid; av. number Cl/molecule: 4.96. d465 1.495; d415.5 1.505. Distillation range 365-390°. No open cup flash point to boiling. nD20 1.629-1.641. Dielectric constant (1000 cycles) 5.0 (25°), 4.3 (100°). LD50 orally in weanling rats: 1295 mg/kg (Kimbrough).
Index of refraction: nD20 1.629-1.641
Density: d465 1.495; d415.5 1.505
Toxicity data: LD50 orally in weanling rats: 1295 mg/kg (Kimbrough)
Derivative Type: Aroclor 1260
Properties: Light yellow, soft, sticky resin; av. number Cl/molecule: 6.30. d490 1.555; d415.5 1.566. Distillation range 385-420. No open cup flash point to boiling. nD20 1.647-1.649. Dielectric constant (1000 cycles) 4.3 (25°); 3.7 (100°). LD50 orally in weanling rats: 1315 mg/kg (Kimbrough).
Index of refraction: nD20 1.647-1.649
Density: d490 1.555; d415.5 1.566
Toxicity data: LD50 orally in weanling rats: 1315 mg/kg (Kimbrough)
CAUTION: In Japan, 1968, oral intoxication to humans due to accidental contamination of rice bran oil with Kanechlor 400 led to an outbreak of what became known as "Yusho disease". Symptoms of oral intoxication in humans included nausea, lethargy, chloracne, brown pigmentation of skin and nails, subcutaneous edema of the face, distinctive hair follicles, excessive eye discharge, swelling of eyelids, visual disturbances, GI disturbances and jaundice. See M. Kuratsune et al., (EPA-560/6-75-004, 1976) p 14. Potential symptoms of occupational overexposure are chloracne, dermal lesions; hepatic injury; decreased pulmonary function; decreased birth weight in offspring of exposed mothers; eye irritation (Safe, 1994). See also Patty's Industrial Hygiene and Toxicology vol. 2D, G. D. Clayton, F. E. Clayton, Eds. (John Wiley & Sons, Inc., New York, 4th ed., 1994) 2433-2504. These substances are reasonably anticipated to be human carcinogens: Report on Carcinogens, Eleventh Edition (PB2005-104914, 2004) p III-218.
Use: In electrical capacitors, electrical transformers, gas-transmission turbines, vacuum pumps. Formerly used in U.S. as hydraulic fluids, plasticizers, adhesives, fire retardants, wax extenders, dedusting agents, pesticide extenders, inks, lubricants, cutting oils, in heat transfer systems, carbonless reproducing paper. |