Document N2Jy4OLgvwZMv8M9mJy9XD1mV

Monsanto FROM (NAME & LOCATION) DATE : SUBJECT : .. W* R. RiCtlSlPCl -- T^A March 24, 1972 PCB REPORT REFERENCE TO : R. H. Munch - 1760 CC: I read through the latest copy of the PCB report. Are you going to have it typed? UO-fc- /is Attach. W. R. Richard OS\N 346586 STLCOPCB4084592 m -4WJTACIL POLYCHLORINATED BIPHENYL BIODEGRADATION STUDIES The threat of continued accumulation of polychlorinated biphenyl (PCB) residues in the environment is responsible for much of the apprehen sion about the future use of these materials. Examination of the data collected to date from both external and Internal PCB residue monitoring programs confirms that at their previous rate of release some persistent PCB homologs have accumulated in the eco-system. Conversely, it can also be stated that, with the exception of direct high level controllable contamination, PCB homologs with less than 5 chlorine atoms have not accumulated in the eco-system1although they have been released in an unrestricted fashion for many years. This observation indicates that at the previous rate of release an environmentally compatible PCB product would be one containing no PCB homologs with greater than four chlorines per molecule. As has been previously stated, it is not commercially feasible to produce a product completely free of the persistent homologs. However, it is technically feasible to produce an industrially useful PCB product, Aroclor 10l6, which contains significantly (10 to 20 times) lower levels of these persistent homologs. Two questions remain which must be answered, first to what degree is biological degradation responsible for the disappearance of the "non-persistent"PCB homologs, and secondly, with controlled and restricted usage, will Aroclor 1016 be environmentally compatible. In an attempt to answer these questions, a number of comparative experimental laboratory studies of the Aroclor products have been carried out to determine the extent to which these materials are degraded by bacterial avian and mammalian organisms. ~ Bacterial Degradation - Semi-Continuous Activated Sludge (SCAS) Degradation Studies of Polychlorinated Biphenyls ~ Introduction The semi-continuous activated sludge (SCAS) test procedure used to study the primary bacterial degradation2 of polychlorinated biphenyls is patterned after the test method recommended by the sub committee on biodegradation test methods of the Soap and Detergent Association for the evaluation of surfactants3. This procedure employs sludge from a sewage treatment plant as the source of microorganisms. A specific amount of the material being studied and a synthetic sewage mixture1* are fed, on a periodic basis to the activated sludge in a specially designed aeration chamber. Aliquots of the mixed liquor (sludge + water) are withdrawn from the chamber shortly after feeding and near the end of the aeration period and analyzed to determine the disappearance rate of the test compound. This cycle is continuously repeated until a steady state5 is achieved and consistent biodegradation rates are obtained. Details of the procedure may be found in the attached Analytical Chemistry Method 71-32. DSW 346587 Summary and Conclusions SCAS testing of Aroclor 1254, Aroclor 1242, Aroclor 1016, MCS 1043# and /Inu.-I.nr 1221 were carried out over an eight-month period. I STLCOPCB4084593 Dlsnppcnrnnrc rate data were obtained during two sampling periods for Aroclor .125*1 > Aroclor 1242, Aroclor 1016, and MGS 10*15. For Aroclor .1221 only one sampling period was employed. In the initial testing of these materials, a feed rate of 1 mg per 24-hr. cycle was used. Because the data obtained from the first sampling period for all PCBs studied, except Aroclor 1221, were extremely erratic with little apparent biodegradation, the exposure period between additions of the test material was extended to *l8 hours for all materials except Aroclor 1221. Statistical analysis of the disappearance rate data from the last sampling period yielded the following mean disappearance rates in per cent for *l8 hours exposure and 95%> confidence limits: Aroclor 12^4 - 15.2 + 57.7 (48-hr. cycle); Aroclor 1242 -26.5+15.5 (*l8-hr. cycle); Aroclor 1016 - 52.9 + 15.0 (48-hr. cycle); MCS 10^15 - 56.2 + 15.5 (48-hr. cycle*)*; Aroclor 1221 - 64.0 + 15.6 (24-hr. cycle). The biodegradability decreases going from Aroclor 1221 to Aroclor 1254, i.e., with increasing levels of chlorination. Because of the uncertainty of the data, it was not possible to differentiate between Aroclor 1242 and Aroclor 1016 with respect to biodegradability at the 95% confidence level. This is not sur prising since 1016 constitutes 80/ of 1242 and the resolving power of the method is comparable to the difference. * Electron-capture gas chromatography analyses of samples taken at the end of the aeration cycle show that the lower the level of chlorination the greater the changes in the homolog distribution. For Aorclor 1221, the dominant monochloro- and dichlorobiphenyl homologs almost completely disappear after 24 hours of exposure to activated sludge. There is, however, a change in ratio of the higher chlorinated homologs to lower ones compared to the distribution in the starting material. For Aroclor 1254, there is no significant change in the homolog distribution after 48 hours exposure compared to the starting material. - At the feed levels employed, no toxic effects toward the activated sludge were observed for any of the test compounds. ' Results and Discussion The sampling and analytical procedures employed in the disappear ance rate determination of a test compound during a cycle were as follows: A 20-ml. sample of the mixed liquor (activated sludge + liquor) was withdrawn one hour after feeding and at the end of the aeration period. The sample of mixed liquor was then extracted and the extract concentrated according to the procedure given in Analytical Chemistry Method 71-18. The concentration of test com pounds was then determined either by an ultraviolet (UV) spectroscopic or electron-capture gas chromatographic (EC-GC) method. Details of the UV methods are given in Analytical Chemistry Method 71-17 and the EC-GC methods in Analytical Chemistry Method 71-55. The disappearance rate was calculated from the following equation: % Disappearance Rate = Co-Cn/Cn X 100 Where Co = level of test material present after feeding , Cn level of test material present after n hours '' of exposure DSW 346588 STLCOPCB4084594 -3- Tcstr. were carried out to determine if quantitative recovery of the variour, test materials from the mixed liquor was achieved by the extraction procedure. Details are Riven in Analytical Chemistry Method 71-17. Although complete recovery was not achieved, the recoveries were consistent and independent of level concentration. The calculated disappearance rates should, therefore, not be affected significantly. Since the level of chlorination is the most significant factor in the relative biodegradability of the PCBs, the homolog distribution of the various test materials is given in Table I. Feeding of the Aroclor 1254, Aroclor 1242, Aroclor 1016, and MCS 1045 units was started on 8/10/70 at a feed level of 1 mg per 24-hr. cycle. These units were samples for approximately one month starting with the first day of feeding. All analyses were carried out by electron-capture gas chromatography. The data obtained were extremely erratic. A statistical analysis of the data (Statistics' Special Study 70-22) using the Student's t test indicated that at the 95$ significance level, only MCS 1043 showed evidence of biodegradation. Both Aroclor 1016 and Aroclor 1242 showed some evidence of biodegradation, but neither was significant at the 95$ level. Aroclor 1254 showed no evidence of biodegradation. In order to detect biodegradation at the 95$ level of significance in 20 observations, about one-half of the test materials must be degraded in a cycle. The lack of significant biodegradation during the first sampling period was probably due in part to the need for an acclima tion period by the bacterial sludge. Subsequent spot checks on the unit, however, indicated that the data obtained was still erratic. Because of the apparent slow rate of biodegradation of these materials, the cycle time was increased to 48 hours in the hope that larger differences would be observed. Feeding of the Aroclor 1221 unit was started on 10/27/70 at a feed level of 1 mg per 24 hours. Aroclor 1221, because of its higher rate of disappearance was maintained on the 24-hour cycle. Sampling of the unit was started 1/25/71 and completed 1/29/71. Analyses were carried out by electron-capture gas chromatography. The final sampling period for the Aroclor 1254, Aroclor 1242, Aroclor 1016, and MCS 1043 units at a feed rate of 1 mg per 48-hour cycle was started 2/8/71 and completed 3/8/71. Both UV and EC-GC analyses were carried outj the UV data was used to determine the overall disappearance rate and the EC-GC to monitor the change in homolog distribution. 1 DSW 346589 STLCOPCB4084595 -4- TABLE I HOMOLOG DISTRIBUTION OF POLYCHLORINATED BIPHENYL PRODUCTS Homolog No. of Cl Per Biphenyl Molecule 0 1 2 3 4 5 6 7 8 9 10 Aroclor 1254 (54% Cl) 0.05 0.06 0.32 0.78 22.99 47.38 19.75 4.62 3.96 Aroclor 1242 (42% Cl) 0.01 0.70 15.50 49.40 24.80 8.70 0.85 MCS 1016 (41% Cl) 0.02 1.00 19.70 57.30 21.20 0.80 0.05 MCS 1043 (30% Cl) 0.11 23.4 71.3 5.2 Aroclor 1221 (21% Cl) 19.00 54.10 20.40 3.90 2.30 0.25 In Figures 1-1 to Figure 4-2, the observed data from which the mean disappearance rates were calculated are shown for both sampling periods for Aroclor 1254, Aroclor 1242, Aroclor 1016, and MCS 1043. In Figure 5, similar data for Aroclor 1221 is shown for a single sampling period. In the top chart of each figure the total mg found in the unit at the beginning and end of each cycle is plotted versus the elapsed time in days after the start of the test. The after feeding sample is denoted by the solid circle; the before feeding sample by the arrowhead; the connecting line indicates the amount lost during each cycle. In the lower chart of each figure, the disappearance rate obtained is plotted versus elapsed time. In Table II the mean dis appearance rate and 95% confidence limits obtained for the test compound during the various sampling periods are given. Since the analyses for Aroclor 1221 were carried out by EC-GC, the disappearance rate does not include any decrease in the biphenyl component (see Table I for Aroclor 1221 composition). In order to make certain that the observed disappearance rates were not due primarily to volatility losses, scrubbing experiments on the most volatile test material, Aroclor 1221, were carried out in which the off-gases from the units were passed through a series of three hexane scrubbers during several complete time cycles. In order to make certain that the observed disappearance rates were not due primarily to volatility losses, scrubbing experiments on the most volatile test material, Aroclor 1221, were carried out in which the off-gases from the units were passed through a series of three hexane scrubbers during a complete time cycle. Data were obtained at both 0.1 and 0.5 SCFH aeration rates. The data established that at the 0.5 SCFH air flow volatility losses were *^16% at an aeration rate of 0.1 SCFH (the volatility losses were a factor of five less) while the overall disappearance rate was essentially the same as that obtained at 0.5 SCFH. This means that the components lost by volatili zation are for all practical pruposes completely degradable and the disappearance rate (64.0%) obtained represents actual biodegradation. Since the volatility of the PCBs decreases with increasing level of DSW 346590 STLCOPCB4084596 chlorination, the volatility losses should likewise decrease. From the volatility losses observed for Aroclor 1221, one would not expect such losses to be a significant factor in test disappearance rates for MCS 1043, Aroclor 1016, Aroclor 1242, and Aroclor 1254. From the data in Table II and Figures 1-1, 2-1. 3-1, 4-1, it is quite apparent that the disappearance rate data obtained for Aroclor 1254, Aroclor 1242, Aroclor 1016, and MCS 1043 during the first sampling period was very erratic. The data obtained during the last sampling period as shown in Table II and in Figures 1-2, 2-2, 3-2, 4-2, and 5 was a significant improvement. From the latter data, the following ranking in terms of biodegradability can be made: Aroclor 1221>MCS 1043>Aroclor 1016 ^ Aroclor 1242>Aroclor 1254 In Figure 6, the mean disappearance rate is plotted versus the per cent chlorine in the test compound. The 48-hour value for Aroclor 1221 was obtained by extrapolation of the 24-hour cycle data; the value for biphenyl was obtained in a previous study (Statistics Special Study 71-2). It is apparent that the disappearance rate decreases with increasing levels of chlorination. As was previously noted, selected samples from the last sampling period were analyzed by EC-GC to monitor changes in homolog and isomer distribution. In Figure 8, chromatograms for Aroclor 1221 are shown. The top trace is a chromatogram of an Aroclor 1221 standard representa tive of the feed material. The center chromatogram is that of a sample taken at the end of the exposure period or aeration cycle. The bottom chromatogram is that of ah Aroclor 1242 standard run under the same GC conditions as the other chromatograms. The numbers above each peak indicate the dominant homolog represented by that peak according to GC-mass spectroscopic determination. It is important to note that the electron-capture detector does not have the same response for all components. The sensitivity of the detector generally increases as the degree of chlorination increases. From the chromatograms in Figure 7, it is apparent that the dominant monochlorobiphenyl and dichlorobiphenyl components of Aroclor 1221 have alsmot completely disappeared after a 24-hour cycle, while there is an apparent buildup of the minor higher chlorinated isomers. These minor components, because of the increase in detector sensitivity with chlorination level, are amplified in the chromatograms compared to ' their true weight per unit basis. Comparison of the extract chromatogram to that of the Aroclor 1242 standard shows that these minor components . in Aroclor 1221, which are more resistant to degradation, comprise the major components of Aroclor 1242. In Figure 8, similar chromatograms are shown for MCS 1043. Comparison of the extract chromatogram to that of the standard again shows that the lower chlorinated isomers or homologs disappear more rapidly while a buildup of higher chlorinated components occurs. 0S>N I STLCOPCB4084597 6- - TABLE II SCAS MEAN DISAPPEARANCE RATES FOR POLYCHLORINATED BIPHENYL PRODUCTS* Sampling Period/ Cycle Time 1/24 Hours Mean Disappearance Rate +95% Confidence Limits Aroclor 1254 Aroclor 1242 MCS 1016 MCS 1043 Aroclor 1221 -29.0+58 11.0+19.5 3.6+19.0 4.7+22.0 2/24 Hours 64.0+13.6 3/48 Hours 15.2+37.7 26.3+15.3 32.9+13.8 56.2+15.5 identification of feed material in SCAS tests Aroclor 1254 Aroclor 1242 Aroclor 1016 MCS 1043 Aroclor 1221 Lot AK-38 Lot AK-255 Sample No. lf OR 158591 Sample No. 2, OR 158591 Lot AK-2 In Figures 10 and 11, chromatograms for Aroclor 1016 and Aroclor 1242 extracts and standards are shown. With these more highly chlorinated products, the change in homolog distribution are not as dramatic com pared to the lower chlorinated products. The buildup in the more refractory penta- and hexachlorobiphenyl homologs is apparent. For Aroclor 1254, chromatograms have not been included since no significant change in homolog or isomer distribution was observed during the testing period. At the conclusion of the final sampling periods for Aroclor 1254, Aroclor 1242, Aroclor 1016, and MCS 1043, feeding of the test compound was stopped. The units were then monitored over a period of time to determine how rapidly the residues remaining from the various test compounds disappeared. In Table III, the mg of residue found at various time intervals after the last feeding are shown. As expected, the lower the level of chlorination the more rapidly the residue disappears. For Aroclor 1254, it is apparent that no significant decrease in the residue occurred over the period studied. sw 346592 I STLCOPCB4084598 l'a go 6-A o ' *> -3 ^ U 0) to (i) in ct'~1 ct- in o s w w 00M 0&(Tt)) 0r)t a H- 0> 01 > o. o -4 4=- 4=- VO 4=^ VJi VJI v>j MOi ro 4=- o oo vron 4=" mm -4 *= O "'J ro 9 ro VO > > oo 13 ro ro 4=" o ro to ro CO Q> M M M C>4 -4 M H * ro MOS ro Ch oCO (- oMOS tri MMH i. 3 . o o M M o w <* ` * --l o ro VJI o ov 4=- M O 4=- or DSW 346593 i STLCOPCB4084599 k ir.um: j_~i SCAS HIODJiCJUADA'lMON DATA *- -- a:. &o- I I. 1 4 <-1 1.. . i ! i-.. fr ! I I1 i. ;. i1 i' 1 Kean =* -29.0 4- 58 I : : vi` :, I I .* .. -r- ir . * i i' DSW 346594 ,---------------*_-- 10 Elapactl <-o) -T6-- Time (Dayc) t-V) 1-oV "l a ~rI *-------------- a after-start ol" Test I JS STLCOPCB4084600 !' i f :i11:): j j SCAS inODIlFlUAPATJON DATA AROCIiOR 1254 ' 5- H :io: c bO r-< 5- o H h><>' : ?- n> 4rJl aaucU>J (* a0s) a. a, tS o V*. An --r-- HO JeoI*6 . j llff . : ' i ' ;,-.i a to rr ! ; !' i .1 I i: Ii , I ` : . i : ' :i i i; i 'i | , *: . IjI* . ` ! * ::i . ii i I! `I; `1 I' T i;' !I DSW 346595 Mean = lbb . * 57 *7 , tnr ,1 *' ^nnt---------------- - K.lnplied Time (Duyts) uX'tcr XJtart oi Toot I ttA' STLCOPCB4084601 1;: r i > 1111< l. 2.' i .SCA15 niODHC.RADATION DATA AROCLOR 1242 ii I! ' t r .i i. ! "i iI i. r " i \ la ;i --r~ 5 1. : * i < ' --r SC to --r~ 9T i; :.| 1 .. !. ) ! f' :I i . i> iT /r .. i i, ii .i ' i : i1 ' ; . i. I!' i i i: i i .'.i ;! i rv! i: ! i ; | ! I. I I ... i i 1 ! i - ' : i i i r '' t Mean = 11.0 j; 19.5 oS-K *1o . --`isTf t-n --'-------- ----1i*--**-----------*----S--S-)---*>-pr~ j i-lapned Time (Daya) alter Stai't- of Teat r 11> STLCOPCB4084602 I--1 ;li i : SCAS H.I.ODEGRADATION DATA I . . i AROCLOR 1242 , .I 4' ;! c: * i rnHj -i 4O-* E* J Of. --IHI-- --i-- l9o .I * I"" MS, --I-- i ; ; k to i ao) C . aUJ rt i ! 1 ari. cmu'"' H I! i I . ii .. ii ` . 'i ' . i *' i ii . i !i;! I ,: 1 .. i iA: * . t ! I , .1 I I I ii i! ............Hean..*=. 2$J>. + li>.2 Ds W 346397 9 X---------- ~~r-- 5 -f - KfS 5* J.J Elapsed Time (Days) after Start of Test STLCOPCB4084603 k I1 \ I 1! i'icuhi: 3-.1. SCA5 niODKGRADATION DATA '.',/ICS 1016 ' I : " I ' . i I' II *1i0--. !<<. I t IJ 1 "T" ir Tl S \ 1 %r : "I \. j . 36 JJ # J i t*i -j i f i t i i i, i DSW 346598 ii 9 .m-W --- -------- `,1L Elapsed Time (Dayo) alter otart5 oi' Test '* I i' ---- *j r. STLCOPCB4084604 I u kici tin: 3-2 \ I' 1 :i i. I fiCAS DIODIXJRAUATXON DATA ' ' . ji " mMaCi Sr> 11 A011n6I;. I iI Ii II I. i DSW 346599 t-1-O m ns -v-- .* . Elapsed Time (Days) after Start of Tost STLCOPCB4084605 I'lCIMiK 4-] i. it i I o -i l ' DSW 346600 i Moan = 4.7 + 22.0 |p i*4U qIo--\ "i1- -- -------5-,-!?------ ----- ".'f^ Elapoed Time (Days) after Start of Toot I !' STLCOPCB4084606 I'lr.uwi-; .SCAH I!J.OUli'.CiRADATiON DATA 1 ai ^ - nt . r; &- ) o . C. . . nj U nJ <D oo,. (0*U i <0 : ij i *> i i i , . i ; 1 I. : 'i .i ! !.i i : ... ii !, IIi Ii i t* : , i Mi-:: i| !. i i, i Mean = b6.2 + I. i 'J . ' ii t I'M DSW 346601 --r-- 11* 1 Elapsed Time (&yo) after ^Jtart *05 of Tout mo. STLCOPCB4084607 1 f.iii'i: r> SCAM HIODKGKAI>AT.TON DATA AROCLOR 1221 , t Xc5tal 5 in" ^D isa p p e a ra n ce Rate 11 ID t>.r o , . - I, I t, , i 1. "T- -1-- So 1 ~r* ~l-- 1 1 9c -Mean 64.0 + 15.6 fo J - / .1 : 1 '' I. I. DSW 346602 e t........ -- -- h ' " r' -t-- 77 *0 7* A 0 Elapsed Time (Days) after' Start of Teat I STLCOPCB4084608 1' : FIGURE 6 'i _ SEMI.-CONTINUOUS ACTIVATED SLUDGE (SCAS) DEGRADATION OP POLYCHLORINATED DIPHENYLS IA I STLCOPCB4084609 'A ro c lo r 1221 Standard M inutes '0 % % - \ \ \ 3 K. \3 S X 0 STLCOPCB4084610 Fjr&un B J___--L-'.".VI j.. ~ i Of2 Minutes 3 ~ 1------ i ......i V S C, . \ I-------- 1" 1 7 6 <? /o 0S\N 346605 STLCOPCB4084611 MCS 1016 S ta n d a rd M inutes (U -o - sx - <0 -^ 'D *0 c\i O STLCOPCB4084612 N ^5' <JC \5 STLCOPCB4084613 M inutes