Document qmqa3VkxDY82awOB0eZD6v3mk

c/EPA United States Environments) Protection Agency Municipal Environmental Beeevoh Ufcoratory ' Cincinnati OH 45209 Reference 2 Research ana Development_______________________________________ October 1970 ENVIRONMENTAL RESEARCH BRIEF Background Major Routes of PCB Contamination Research Project Thermal Degradation of PCBs Polychlorinated biphenyls (PCBs). commercially introduced in 1929. were not recognized as widespread environmental contaminants until 1966 Since that time. PCBs have been found in air, water, sediment, as well as plant and animal tissue The major routes of PCB contamination have been summarized by DiNardt and Desmarais.' Industrial smoke from incineration of PCB-containing materials. Pew facilities provide the required decomposition temperature PC8$ also persist in the vapor state, and even if not vaporized, have a strong affinity for particulate matter Waste in rivers and other waterways from the disposal of waste oils, waxes, and paints from industrial or other sources. Landfill leaching from PCB-containing plastics and resins Insecticide runoff of PCBs which are used to extend the kill-life of aldrin. dteldnn. and chlordane, or as a synergist with lindane. Recycling of PCB-containing paper Even virgin paper can be contaminated through manufacturing processes Direct contamination from leakage of heat-transfer fluid, or oils Concentration in biological materials. PCBs are lipid-soluble, and therefore are concentrated in the foQd_chain. They are. concentrated in sewage sludge by lipophilic substances. In addition to their universal distribution. PCBs are among the most siable organic compounds known. They are resistant to biodegradation and are not readily broken down either physically or chemically. PCBs have also been shown to be potent, chronic toxicants1 and have been linked to liver, pancreatic, and skin cancers.3*k Although PCB production has ceased in the United States.* a safe and efficient disposal method must be chosen to eliminate the long-term effects of PCB contam ination The nature of the disposal method is necessarily complex due to the persistency, chrontc toxicity, and stability of the PCB molecule. Because the available literature pertaining to thermal disposal of PCBs covers such a broad range of incineration condi tions. more refined technical data are needed so that the physical parameters necessary for the thermal degradation of these substances can be defined. The research discussed here7 was initiated to ascertain high-temperature destruc tion properties of PCB mixtures end related compounds. The laboratory procedures involved the use of small quantities of commercial mixtures and pure isomers of PCB in a precisely controlled thermal environment. The specific objective of the laboratory effort was to establish the thermal destruction characteristics of vaporized PCB samples at preselected residence times. The approach for obtaining high-temperature destruction data on Hie PCBs involved the use of a discontinuous system in which thermal stressing of the sample and product analysis were performed separately. With this approach, various PCB isomers and related compounds were evaluated in a series of tests wherein the sample was first vaporized and then transported through a narrow-bore, high-temperature zone by a controlled flow of air In this way. average temperature and residence time relationships were established over the range 300C to 1000C It is important to note that this study focused on the loss of the parent molecule and not on the identification of the decomposition products figure 1 is a schematic of the high-temperature quartz tube apparatus designed and assembled by researchers at the University of Dayton Research Institute under a grant from the Solid and Hazardous Waste Research Division (SHWRD) The instrumentation and associated procedures used on the PCB samples were those used for Kepone. Mirex. and DDT.9 The effluent from each high-temperature test was subsequently passed through a trapping medium and the collected fraction analyzed by gas chromatography Summary of Result* o c c e r^\ A /--------- 1 UK i H -- i " --^ i"~HTni]uiiiiii HIGH temperature REGION - ! u1 . a COMPRESSED AIR. breathing QUALITY GRADE B TWO STAGE PRESSURE REGULATOR c "HVDROPURGE" FILTER 0 FLOW CONTROL VALVE E PRESSURE TRANSDUCER f SAMPLE HOLDER PVRtX G HEATEO INLET CHAMBER H Quartz tube 1 HEATED INLET CHAMBER J EFFLUENT trap TENAX GC OR CHARCOAL K FLOW METER Figure 1. Schematic of Ouaru Tube Apperetut. The data generated ware tabulated and thermal destruction plots were prepared for representative PCB samples (Figures 2 and 3) Biphenyl, the nonchlorineted PCB skeleton, end decachlorobiphenyt, the most highly chlorinated PCB, are presented irv both figures ss references for the extremes of the PCB family Figure 2 also illustrates the decomposition profile of two commonly occurring isomers ol PCB contamination. 2.S.2',5'-tetrachlorobiphanyl and 2,5,2',4',5*-pentachtorobiph#nyl Tetrachtorobiphenyl is less thermally stable-than pentachlorobiphenyl, which in turn is less thermally stable than decachlorobiphenyt. Figure 3 presents the decomposition profile of two nonchlorineted species, dibenzofuran and dibenzo-p-dioxin, the chlorinated analogs of which are highly toxic, ft should be noted that the nonchlorineted species have similar thermal stability, and that hexachlorobenzene and decachlorobiphenyt have approxi mately the same thermal stability. For the PCBs and their related compounds, no thermal breakdown occurred at temperatures below 550C. Interestingly, the PCB and like compounds underwent considerable degradation from 640C to BOOC. a rather narrow range. The effect of residence time on the thermal destruction of the PCB samples was evaluated. Tests were conducted at a tamparatura of 704C. a temperature lass than that required for complete thermal decomposition. The air flow rates passing through the quartz-tube apparatus were altered to obtain different residence times at the fixed HONS 009255 temperature The effluents were analyzed and thajdsta presented in log-log form (Figure 4) It is evident from this plot that residence Time is definitely a strong factor effecting the high-temperature destruction of PCBs and related compounds i t 5 1 s EXPOSURE TEMPERATURE C Figure 2 Thermal Destruction Profiles of PCS Isomers and . Sphny< Ftgurs 3 EXPOSURE TEMPERATURE C Thtrmal Destruction Profilaa of Compounds Related to PCS Mixtures Conclusions The following conclusions have been drawn from this study of the thermal degra dation of PCBs and related compounds 1 Commercial PCBs undergo decomposition in air between 640C and 740C at a residence time of 1 second. PCBs exposed to high temperatures (1000C for 1 second in air) yield a destruction percentage of 99 995 2 Residence lime is a strong factor in the high-temperature destruction of PCBs 3 Upon thermal stressing in air. PCBs decompose to low-molecular weight prod ucts. 4 For a given thermal exposure, the lower molecular weight PCBs are less ther mally stable then the higher molecular weight PCBs. 5 Compounds related to PCBs -- biphenyl, dibenzofuran. dibenzo-p-dioxm, and hexachlorobenzene -- demonstrate thermal destruction properties comparable to ihose of PCB mixtures. Figure 4. Effect of Residence Tint* on the Thermal Des truction of PCB Itomart and Related Compound*. HONS 009256 Future Rtttarch References The work reported here represents high-miensity effort and further study >s needed Suggested additional work includes Development of a closed system for the analysis of samples in a combined thermal destruction - gas chromatograph mass spectrometer system to identify degradation products and effluents Determination of a more quantified effect of residence time on PCBs at a variety of exposure temperatures. Assessment of the thermal stability of PCBs and ralatad compounds at tempera lures near 1150C. Comparisons of the thermal destruction behavior of PC8s and related com pounds m moist tic with their behavior in dry air Correlations of the results of the non-flame mode of destruction with those of the flame mode. A more complete explanation and presentation of the material discussed here can be found in Laboratory B valuation of High Temperature Destruction of Polychlorinated Biphenyls and Related Compounds A copy of the report can be obtained from the Tech nical Information Operations Staff. Environmental'Research Information Center. US Environmental Pr* ancy, Cincinnati, Ohio 45268 t DiNurtfi. S R indA M 49(41 p 14 17 1976 Polychlorinated Biphenyls in the Environment Chemistry 2 Umeda G PCB Poisoning in Japan Ambio, t|4|, p 132. 1972 3 Kimbrough. R D and R E Linder Induction ol Adenohbrosis and Hepatomas of the liver mBAlB c* Mice by Polychlorinated Biphenyls tArochlor) Journal of the National Cancer Institute 53 p 547 1974 4 Behn A K 1 Rosenweike, N Herrman P Grover. J Stetiman. and K Oleary Melanoma after Exposure to PCBs New England Journal of Medicine. 295. p 450. 1976 5 Is There a Carcinogen Threshold limit? Chemical Week. 119f12l p 29 1976 6 Monsanto to Quit PCB Butmtss Next Year Chemical and Engineering News. 54(421 p 8 1976 7 Puvati D S andW A Rubey LaboratoryEvaluanonol High.Temperature OestruciionolPoiychior> naied Biphenyls and Related Compounds EPA-600 2-77-278. December 1977 B Ouvall D S andW A Rubey leboreiorvEveluetionofHigh-TemperaiureDestrueiionolKtponoend Related Pesticides EPA-600 2-76-299. December 1976 Authors Judith A Mescher4, Richard A. earnest. Donovan S Duvall4, and Wayne A Rubey* 'Research Associates. University ol Dayton Restarch Institute. Dayton Ohio tEnvironmental Scientist. Solid tnd Haiardous Wsste Research Division. Municipal Environmental Research Laboratory. Cincinnati, Ohio IMMSMses twffsansilii Petsctien ORwut Buswnt *MMy fat PlivHS Uw IMO Iwveerswental Rwairtfi trduimatiow Cental Cmcmwii OH 46266 ERIC 01 2*05980 j JXNOolECKl ass ssa^sse JN LAO NICHOLS PD on. oh s*or **ctrve NOV/, 7g Postage ve Fats P*e Pirate mafct all nacasaary changes on me above label detach or copy and return to in# address in (he uppe> ah hand corny* N you do not vih to raee<ve three >epon CHECK h(R( . Oaiaeh or copy tn*ena and (arum to I'v rWru *n me uopar ifh hand corner HONS 009257