Document 50eDVv4YwmQ2pqrYY7ENzMqV0

February 16, 1970 Mr. Harold R. Hoyle Biochemical Researoh Laboratory Dow Chemical Company 1701 Building Midland, Michigan 46640 Dear Harold Although we have developed a tremendous effort in the laat year-and-one-half concerning the polyohlorinated biphenyl interferences in pesticide residue analysis, I have not found any data that would indicate a change in the TLV's for the 42 and 54jf chlorinated materials. I think I have in hand everything that has been pub lished on the PG8-DDT situation and, although there have been references to toxicity studies underway, the latter relate to fish and birds principally. We have supplied samples to several FDA, FWPCA, Fish and Wildlife Servloe Laboratories, NAFCA, etc. and know that only two FDA laboratories are doing straight mammalian toxloity work. We have two-year ohronlo studies underway at C91andra's using rats and dofcs and a three generation rat repro duction experiment In progress. At the moment X don't foresee that the results of these studies should lead to the reduction of TZAT's for industrial workers. The way things are going in the whole field of environmental oontrol, X won't presume to make any suoh statement as a flat prediction. Developments in the ftext six months to year will have a tremendous effect on the relation ship of toxicity in any living species and exposures to numans. Best personal regards. 81ncerely, EFWtJu Elmer F. Wheeler, Manager, Environmental Health DSW 019673 STLCOPCB4007606