Document MoKq18Dngmq8jKEQ8nD6KMv2y

82B1 PES IEEE/PES Conference New York City February 1-5,1982 Dr. Ian Webber Engineering Manager RTE Corporation RTE CORPORATION 1900 E. NORTH ST. WAUKESHA, W1 531M HONS 214004 THE DEGRADATION OF POLYCHLORINATED BENZENES IN ELECTRICAL EOUIPMENT IEEE/PES CONFERENCE, NEW YORK CITY, 1982 The currant legislation governing polychlorinated biphenyl* (PCBs) was precipitated by the Yusho incident in *outhw**trn Japan in 1968. Approximately 1300 people ingested an avecaqe of about 2q each of PCB fluid from a leaking heat exchanger. The first contaminant of the rice oil to be identified waa PCB, and the symptoms of the poisoning were therefore blamed upon PCBs as the causative agent. Subsequent analysis^) of the Yuaho oil haa revealed that the apparent toxicity of the aakarel is likely to have been due to the presence of PCB degradation products such as polychlorinated dibenzo furans (PCDFs}, In 1970 Vos et si'*?) showed a correlation between the toxic effects of European PCBs and the concentration levels of PCDFs. The major PCDF components contained in Yuaho oil were the highly toxic 2,3,7,tt-tetra-CDF and 2,3,4,7,8-penta-CDF. The relative concentra tions of the PCDF isomers present in Yusho oil and in two samnles , of used heat exchanger PCBs {Kanechlor KC 400 and Mitsubishi ' Monsanto T 1248) were found to be strikingly similar.'-*' This fact underscores the findings of other workers in thia field that there is a connection between the toxicity of degraded PCB fluids, in cluding tri-'tetra-chlorinated benzene/PCB blends, and the con centration of PCDFs. The overall toxicity of the fluid may then be attributable, as Vos indicates, to the two particular components mentioned earlier. (1) H. R. Buser, C. Rappe and A. Gar4; 'Polychlorinated Dibenzo Furans Found in Yusho Oil and in Used Japanese PCB"; Chemosphere 7, 439 (1978). (2) J. G. Vos, J. K. Koeman, H. L. Van der Maas, M. C. Ten Noever de Braun and R. H. de Vos; "Identification and Toxicological Evaluation of Chlorinated Dibenzofuran and Chlorinated Naphthalene in Two Commercial Polychlorinated Biphenyls"; Fd. Cosmet. Toxicol. 8, 625 (1970). (3) M. Kuratsun#, y. Masuda and J. Naqayuma; Proceedings of the National Conference on Polychlorinated Biphenyls, Chicago, November, 1975; EPA-560/6-75-004. HONS 214005 Buser ha* shown that the pyrolysis reactions of chlorobenzenes in the presence of air yield tetra- to octa- CDF* and tetra- to octa- CDDs, The experimental conditions used in his laboratory study were intended to provide easily determined concentrations of degradation products (approximately It) within a short period of time. The fluid temperature inside a faulting transformer is not likely to reach 600C for a sufficient lenqth of time to cause the formation of PCDFs, but there may be hot-spot temperatures of 3QQC for significant periods. It is of concern that heating PCBs in air at 3Q0C for only one week is sufficisnt to generate PCDFs(5) in the ppm concentration range. Chlorobenzenes with a higher deqree of chlorination than the compounds used for pyrolysis were observed in each reaction mixture. These must have been formed by a chlorination process from components of the mixture containing less chlorine. However, the formation of chlorobenzenes with less chlorine than the compounds used for pyrolysis was not observed. This may indicate that once the chloro benzene molecule has become reactive by the removal of a chlorine atom the product formed will depend upon the concentration of inter active molecules in the system. In any case, the partially dechlorinated chlorobenzene does react, probably with oxygen, and transmutes to a stable form which is not a chlorobenzene. For example, the reaction mixtures were found to'contain chlorophenols in addition to PCOFs and PCDDs. It was therefore suggested that the reaction of chlorophenol with chlorobenzene could lead to polychlorinated diphenyl ethers (PCDPEs) which are known to form PCOFs upon pyrolysis. This mechanism does not seem probable, however, because PCDPEs were not detected. PCOFs and PCOOs can be formed from chlorophenols in three ways. (1) The dimerization of chlorophenates. (2) The cyclization of PCDPEs. (3) The cyclization of polychlorinated phenoxy phenols termed "pre-dioxins*. The dimerization of chlorophenates is likely to be bimolecular and therefore the products formed should be highly dependent upon the chlorophenate concentrations. The PCOO isomers formed in the system, and their quantities, will depend upon the relative kinetics of the alternative reaction routes. It would be expected that the relative importance of the bemolecular mechanism would decrease with the concentration of chlorophenatss. (4) H. R. Buserj "Formation of PCOFs and PCOOs from the Pyrolysis of Chlorobenzenes": Chemosphere, 8, 415 (1979). (5) H. R. Buser and C. Rapp*; "Formation of Polychlorinated Oibenzofurans (PCDFs) from the Pyrolysis of Individual PCS Isomers"; Chemosphere 8, 157 (1979). (6) C. Rappe, S. Marklund,-H. R. Buser, H. -P. Bosshardt; "Formation of PCDDs and PCDFs by Burning or Heating Chlorophenoles"; Chemosphere 7, 269 (1978). HONS 214006 The pyrolysis of PCDPEs follows two competitive reaction pathways viz., reductive dechlorination or ring closure to dibenzofurans. This is not likely to be an important route in the laboratory pyrolyses because of the apparent absence of PCDPEs. The cyclization of pre-dioxins is a molecules reaction caused by heating. The final concentration of dioxins in- the heated chloro benzene system should ultimately be dependent upon the concentration of polychlorinated phenols which are formed. The presence of chlorobenzenes and chlorophenols in the product mixture which contain a higher degree of chlorination than the chlorobenzenes in the starting mixture indicates the probability of free redical reactions. Louw, Rothuizen and wegman^) have interpreted the pyrolysis of chlorobenzene as a radical chain reaction involving CSH4C1, .Cl and H* as carriers. _ The authors discuss a radical reaction sequence which explains the observed product pattern, including the formation of PCBs. The pyrolysis of PCBs occurs intramolecularly by four alternative reaction routes to yield different isomeric PCDF products.The extent to which the free radical reactions yield PCBs and the extent / to which the eventual cyclization of the PCBs contributes to the overall yield of PCDFs is probably small. Indeed, the quantities of PCBs detected were small. The formation of polychlorinated naphthalenes in Buser's experiments (Ref. 4) can be explained by either invoking the formation of benzyne intermediates or the re-arrangement of intermediates formed between an ortho-ehloro phenyl radical with a chlorobenzene. The overall effect of radical reactions on the product distribution in a pyrolysis reaction will be effected by both temperature and the availability of oxygen. No work has so far been done to examine the effects of these parameters on the total quantity of PCDFs produced. (?) A. Norstrom, K. Andersson and C. Rappe; 'Studies on the Formation of Chlorodibenzofurans by Irradiation or Pyrolysis of Chlorinated Diphenyl Ethers'; Chemosphere, 241 (1977). (8) R. louw, J. w. Rothuizen and R. c. C. Weqman; "Vapour Phase Chemistry of Arenes. Part II. Thermolysis of Chlorobenzene and Reactions with Aryl Radicals and Chlorine and Hydroqen Atoms at 500"; J, Chem. Soc. Perkin Trans., 2, 1635 (1973). (9) H. R, Buser and C. Rappe; "Formation of PCDFs from the Pyrolysis of Individual PCB Isomers'' Chemosphere, 8, 157 (1979). HONS 214007 r Morita(1) and Nagayama(11) have determined the concentration! of PCDFa in "Yusho oil" and in new European and Japanese PCB sample!. The combined concentration of the different isomers identified in the unused PCB samples was from 1-24 ppm, while in Yusho oil, the concentration was reported as 2700 ppm in Ref. (10) and 5000 ppm in Ref. (11). The concentrations of PCDFs in new and used PCBs is shown in Table (1). The PCDFs in the unused PCBs were probably formed by the chlorination of dibenzofuran as an impurity in the original biphenyl. Chittim, Clegg, Safe and Hutzinger have analyzed unused North American askarels (Interteen, pyranol and Chlorextol) and foundU2) that they contained leas than O.OS ppm. Aa stated earlier, Vos et al have foundthat the toxic effects of PCB based fluids could be corralated with the levels of PCDFs contained in them. It is therefore of considerable concern that, in Ref. (12), it was determined that the level of tetra-CDF in an aakarel was found to increase as the time since the transformer was installsd increases, see Fig.(1). The small number of samples tested were Insufficient to obtain a definite, correlation between kVA and oil volume, manufacturer and fluid type or TCDF concentration and transformer loading. While the results indicated that transformer load is probably a major factor in the formation of PCDFa, the effects of discharging or arcing appeared to be negligible. Chittim et al have concluded that the PCDFs found in the oil were probably produced during the normal operation of the transformer ) and that a number of different variables all contribute to the formation of PCDFs. In particular, it was observed that the samples which contained the most polychlorinated benzenes also had the higher TCDF concentrations. Thus, the presence of certain polychlorinatad benzenes may be the major contribute! to th formation of PCDFs in transformer askarels. The results of different studies on the formation of PCDFs in chlorobenzene/PCB fluids are shown in Table II to IV. A list of the reactions involved in the formation of toxic products is given in Table V. (10) (11) (12) M, Horita, J. Nakagawa, K. Akiyama. S. Mimurz and N. Isonoi "Detailed Examination of PCDFs in PCB Preparations and Kanemi Yusho Oil*j Bull. Environ. Contam. Toxicol.; 1, 67 (1977). j. Nagayama, M. Kuratsune and Y. Masusda; "Determination of PCDFa in Kanachlors and Yusho oil"; Bull. Environ. Contam. Toxicol. 15, 9 (1976). 8. G. Chittim, B. S. Clegg, S. H. Safe and 0. Hutzinqer; "Chlorinated Dibenzofurans and Dibenze-p-Dioxinsi Detection and Quantitation in Electrical Equipment and their Formation During the incineration of PCBs."; Report prepared for Fisheries and Environment Canada, under Contract No. 05578 00067; September 1979. HONS 2U0Q8 PCB NEW: Aroclor* 1254, 1260(11> Clophen Phenoclor dp-6<13) T 1242<*> T 1248(3) T 1254<*> T 1260<> Kanechlor 200 Kanechlor 400(9> Kanechlor 500*9* Kanechlor 600*9) USED; T 124i<9) Aroclor 1254 <U) Aroclor 12M*11! Y'atho Oil PCB (KC400) TABLE Polychloro Oibenio Furans CIS Cl6 1.4 0.7 2.3 0.5 0.1 0.* 6.7 12.2 1.7 0.2 * 5.8 5.0 10.0 2.2 2.3 3.6 0*9 1.6 10.4 1.1 0.5 5.6 2.2 2.9 1.9 0.5 '0.9 3.1 0.4 0.7 520 1330 810 - Total < 0.05 8.4 13.6 4.5 2.8 5.6 2.2 8.3 23.8 6.1 1.1 12.4 0.55 1.1 2680 (13) C. W. Bowes, M. J. Hulvihill, B, R. Nature, 254, 305 (1975). Sleoneit. A. L. Burlingame and R. w. Risebrouqh, MOMS 214009 Chlorobenzene Studied Mixture of trz-/tetrachlorobenzene; pentachlorobenzene Monochlorobenzene Monochlorobenzene TABLE II Chlorobenzene pyrolysis Process Pyrolysis in air Product(s) PCDD, PCDF, PCB, higher chlorinated benzenes, Cl phenols Yield 2,000 ppm Ref 4 Pyrolysis in "2 Mono- and di-Cl biphenyl Pyrolysis di-Cl biphenyl 50 ppm 10% 8 14 (14) C. F. Cullis and J. E. Manton: Trans. Faraday Soc. 54. 381 (1958) HONS 214010 Chlorophenols Studies Various triJ, tetra- and pentachlorophenols Trichlorophenol Tetrachlorophenol 2,4,S-Trichlorophenol ichloropheno1 2,3,4,6-Tetrachlorophenol TABLE III Chlorophenol Pyrolysis Process Product(s) Pyrolysis Various PCDDs Pilot Beale combustion on wood chips Pyrolysis Mainly TCDDa - Mainly HCDOs 2,3,7,8-TCDD 2,4,7,9-TCDO 1,3,4,0,0,9-HCDD Weld 3-10* Ref 15 230 ppm 16 3S0 ppm 1* up to IS* 17 30* (IS) (1) (17) H. R. Buser; "Separation and Identification of PCDDs by Gaa Chromatography - Mass Spectrometry"; J. Chromatogr., 1^4, 95 (1975). b. Jantson, C. Sunditroa and B. Ahling; Sci. Total Environ. 10, 209 (1970) . M. G. Langsr, T. P. Brady and P. R. Brioqs; Environ. Health Perspect. 5, 1 (1973). MONS 214011 Chlorobiphenyl Studied 18 different chlorobipltenyls containing 4,5,6,7 and 8 Cl atoms 2, 2l, 6, 6l - TCB 2, 21, 4, 4l. 5. S1 - HCB 2, 21, 4, 41, 6, 61 - HCB Arochlors 1248 and 1240 Archlor 1248 TABLE IV PCB Pyrolysis Process Product(s) Pyrolysis in air -PCDP , Pyrolysis in air PCDP .2,3,7,8-TCDP Pyrolysis in air in <>2 in "2 PCDP Yield 0.1-lt Ref. 5 2% 18 28 300 ppm 1100 ppM 2 PPM 19 (18) H. R. Buser, H- P. Bosshardt, C. Rappe and R. Lindahl; Chsansphere, 7, 419 (1978). (19) H. Morita, J. Nakagawa and C. Rappe; Bull. Environ. Contan. Toxicol.; 19, 649 (1977). HONS 214012 TABLE V (1) Formation of chlorophcnols: (2) Formation of polychlorinated dipehnyl ethera/PCDF*: opl -w PCDD (4) Cyelization of polychloro phanoxy phanolst HONS table V (cont1d) HONS 214014 /> *) ) Yetrs Jin Service HONS 214015