Document rZbqN2LLoXGZ3Byqeg0gLkRJ

Monsanto ttti'.uiCAUi i,ro. kjiom <i.(PaTIOn; li. A. VJJOEN - KUABQN. OaTR . oia;iar,y 1972. HutuKCT Yo'jt letter of 10 January, 1972. HWKKHKm-K HAV/l). O',?. TO : H.H. MUNCH - ST. LOUIS. CC t N.H. Ha chard - dt. wu.-, R.A. Baxter - Ruabe- . 2.S. 'PucKer - St. l; uj m. Dear Ralph, j appreciate your concern at not receiving the additional data lor Paolc* 5, Appendix 2 of our joint PCB report. .`Unfortunately, the results of the wortc in hand did not furnish tn*1 information I had anticipated and we have been unable to reduce in.* da "a tc ninipli} tabular form. He find, for example, when 10^ of Aroclor i.;A pc adued to Aroclor 1242 to increase the percentage of higner homologies pritn' that degradation of the whole Aroclor composition is inhibited. r, otrvr words, a sufficient concentration of more highly chlorinated Aroclor appears to behave aa a bacterioatat towards the Cj and C3 cultures. fn the presence of a low concentration of these more highly chlorinated hon.oJogues, such as in Aroclors 1016 and 1242, however, the cultures C, 1 and C. appear to degrade all the isomers present in significant quantities, including sene penta and hexachloro-components, with half-life periods of less tfiuri $0 days. Vs have just completed some of the tests leading to this conclusion and have more in progress to confirm tne level at which bacteriostatic action occurs in a PCB mixture. It appears, therefore, that we cannot specify, even approximately, the degradation rates of PCB homologues without taking into account tn*: *ff`ctr of otJvr PCB components. This makes it impossible to compile a simple table of degradation rates for insertion into a mathematical model of the type we discussed with Jack Hinchen. This work may al3o- explain the discrepancies in results to which you WiVr it* .your letter. In a mixture, the adaptation process may p<. rmit degradation of oertain isomers which in isolation might be resistant, (e.g. 4-'1'diuhiorobiphenyl in the presence of C2), but if significant quantities of highly chlorinated biphenyl are present, the degradation of many other isomers may be inhibited or slowed down. 1 do riot think these findings invalidate the concepts behind Aroclo- r indeed t.iey seem to mi to strengthen its position, but presentation of tho reuuiui, in a way which allows a rational interpretation, po3s ron.> difficulties. I am rewriting the oection of Appendix 2 concerns wir.ii th* results on commercial mixtures and the discussion to take account of th^se recent findings. J whs glaa to Learn that the appendices on analytical metnodoiow have hern completed and look forward to seeing these. Do we mow -..tve a -< votimatn of tht- distributions of homologues being used before and ftor the Monsanto action and can we estimate the probable inputs to the env. roumimt? Mil. MONS 09945l in re ply to your other questions the answers' to 1, ; and ^ am yrr*., Question 4 'nay bo answered in part by the precoeuj.n{i: sagfeations, L.it hJijo to noni extent by the way in which the rates are derived fro-r. the oxn'.'rim''M.al results* We now have several more points on the degradation curver, tor the various isomers and will use these to provide* hop'd'uiiy , mom accurate c.ata. Regards and best wishes, L'arCtU^. H.A. VOCDEN. MOHS 099*51