Document NGMoDQ2pGyypj5EZRy75LxBop

Juno 8, 1962 J-V -!(> ~ c >/ A/7// Dr. Herbert H. Stokinger, Chairman Threshold Limits Committee American Conference of Governmental Industrial IIygienlst3 U.C. Public Health Service 1014 Broadway Cincinnati 2, Ohio Itear Herbs I am finally getting around to answering your letter of May 4, 1S'j2, in which you ask for any comments relative to questions about vinyl chloride and boron trifluoride. I wanted to gat to talk to you about these when we were in Washington, but somehow or other thi3 was one of the things 1 failed to do. In regard to vinyl chloride, I have again reviewed our pub lication and the data upon which our conclusions were based. I believe we have described our findings in adequate detail to allow an individual to draw his own conclusions with re gard to what limits he wishes to apply in his situation. There is no doubt that the effects produced at 200 and 100 ppm in our laboratory were minimal. At 200 ppm, you will note that we had some histological changes in rabbits and organ weight changes in rats. At 100 ppm, the organ weight change in the livers was the only adverse effect. We have interpreted such a change as being evidence of stress*and we question the desirability of placing that stress on the human unnecessarily. I have no explanation for the discrepencies between our findings and those of Lester and Greenberg and unfortunately I did not hear their paper in Washington. I hope that I will have an opportunity before too long to re view their complete paper and to see under what conditions and upon what basis they reached the conclusions they did. If you have a copy of this paper, I would certainly appreci ate having an opportunity to see it* In answer to your direct question, I do not believe that in our studies there were effects produced by infective pro cesses or other chemical agents to account for our findings. I guess my position is that 1 will check and call all bets. In regard to boron trifluoride, we have again I believe, given the results of our findings in sufficient detail to R&S 131893 Dr. H. ii. Stokinger 2 June 8, 1262 allow other persons to draw their own conclusions. They are certainly at liberty to disagree with our conclusions, but as Tar as the data are concerned, I have no reason to believe tliat they are not perfectly sound. In regard to this particular material, we had considerable difficulty early in the came obtaining reproducible analytical results, I an wondering, perhaps, if any apparent discrepancies be tween the animal work and the effects reportedly obtained on humans may possibly be attributed to differences in analytical techniques. Wo have found that this can be quite critical in dealing with such low concentrations of sub stances such 03 BP. 3* I certainly realize. Herb, that I have not given you the answers to your questions, but I have no reason at thi3 time for not standing pat on our data. Interpretation of said data is another matter and you and your committee are certainly competent to do this. I should like very much to receive your comments and If I can be of any further assistance, please do not hesitate to call on me. With best personal regards. Sincerely yours. V. K. Howe Biochemical Research Laboratory 1701 Building VKR/jd cc : V. K. Rowe (2) T3.4-16-20 *----------T34.24-22-20 Correspondence