4,975 to 11,765 mg/kg after use as a heat transfer fluid in a heat exchanger. 

 These PCDFs were identified as the agents that poisoned more than one thousand 

 humans in Japan in 1968 (EPA 1980; Lucier and Hook 1985a, b). Additional 

 research is needed on PCDFs and other toxic impurities in PCBs. 



PCBs are extremely stable compounds, and slow to chemically degrade under 

 environmental conditions. Microbial degradation of PCBs depends on the degree 

 of chlorination and the position of the chlorine atom on the biphenyl 

 molecule; lower chlorinated BPs are readily transformed by bacteria, but not 

 the higher chlorinated compounds (NAS 1979). Higher chlorobi phenyls, i.e., 

 those with five or more chlorine atoms, were more persistent in the 

 environment than those with three or less chlorine atoms; tetrachloro BPs were 

 intermediate in persistence (EPA 1980). Passage of PCBs through activated 

 sludge in sewage treatment plants for 48 hours resulted in 81% degradation for 

 Aroclor 1221 (21% chlorine by weight), 26% for Aroclor 1242 (42% chlorine), 

 and only 15% for Aroclor 1254 (54% chlorine) (NAS 1979). Because of their 

 wide range of physical properties, their chemical stability, and their 

 miscibility with organic compounds, PCBs have been used extensively as 

 hydraulic fluids, plasticizers, adhesives, heat transfer fluids, wax 

 extenders, dedusting agents, lubricants, flame retardants, and especially as 

 dielectric fluids in capacitors and transformers. The current uses of PCBs in 

 the United States have been severely curtailed and production was stopped 

 during the 1970's, although significant quantitities of PCBs are still used as 

 dielectric fluids in older transformers and capacitors (Safe 1984). 



Commercial PCB formulations are sold under a variety of trade names 

 (Roberts et al. 1978; NAS 1979; EPA 1980; D'ltri and Kamrin 1983; Safe 1984). 

 In the United States, Aroclor is the most familiar requested trademark, but 

 PCBs have also been marketed as Chloretol, Dyknol , Inerteem, Noflamol, and 

 Pyranol. In other countries, PCB formulations have been sold as Pyralene 

 (France), Phenoclor (France), Kanechlor (Japan), Santotherm (Japan), Fenclor 

 (Italy), Apirolio (Italy), Soval (USSR), Oelor (Czechoslovakia), and Clophen 

 (West Germany). Some formulations are similar; for example, Kanechlor 600, 

 Phenoclor DP6, Clophen A60, and Aroclor 1260 all contain an average of 60% 

 chlorine, although the former three preparations are composed of a mixture of 

 hexachloro BPs, while Aroclor 1260 contains a variety of forms (Table 1; NAS 

 1979; EPA 1980). 



Chlorination levels of PCB formulations differ markedly (Table 1). Among 

 Aroclor formulations commercially produced by the Monsanto Corporation, 

 Aroclor 1221 contained an average of 21% chlorine by weight and was a clear 

 mobile oil. Aroclor 1254 contained 54% chlorine and was a yellow viscous 

 liquid; 1260 contained 60% chlorine by weight and resembled a yellow sticky 

 resin; and Aroclor 1268 was a white solid (Safe 1984). Aroclor 1254 contained 

 less than 1% of biphenyl and monochloro BP, 0.5% dichloro BP, 1% trichloro BP, 

 21% tetrachloro BP, 48% pentachloro BP, 24% hexachloro BP, and 6% heptachloro 

 BP (NAS 1979). Aroclor 1016 was similar to Aroclor 1242, with both containing 

 an average of about 42% chlorine by weight, although 1242 contained 9% PCBs 

 with five or more chlorines and 1016 only 5% (Roberts et al. 1978). In 

 general, PCBs are relatively insoluble in water but freely soluble in nonpolar 



