Document dQ9dxBeqLqBkJ06a27G9MDDde

JUl i_ * October 29, 1969 Robert J. M. Sorton, ,D. .Senior Research Advisor Division of Effects flttiFwiTgh 4X1 West Chapel Bill Street Durban, north Carolina 17701 Seer Bob* With regard to Or. Tapper's letter of February 4, 1969, X an enclosing aos eoawamts of age, John E. Bernes who ie in charge of oar Chemistry Section. X agree with bis observations end believe that ASA is m good guide in detec- ting persons or grouse who have an exposure to Isadwhich ie too high, hut that there is a level of blood lead below which ALA ie not affeotod and therefore a poor correlation would be expected. Tours sincerely. GJS/bjd Bnels,(2) o r ig in al s ig n ed by G. j. STOPPS a. J. Stepps, H.B.,B.S. Assistant Director cct Lloyd B. Tapper, MUD. JA2 DUP040001934 TO: G. J. STOPPS PROM: j. R. BARNES DATE: OCTOBER 16, 1969 COMMENTS ON THE KETTERING LABORATORY Pb/AIA STUDY Using the criteria that all urine ALA's 5.7 mg/L or higher are abnormal (Haeger-Aronson and DuPont), and all blood Pb's 0,,04 mg/100 g or higher are abnormal (Goldwater and Hoover) then: all 39 specimens had "abnormal" blood Pb's 24 times all three urine ALA's would predict an excessive exposure 28 times two of three urine ALA's would predict an excessive exposure 33 times one of three urine ALA's would predict an excessive exposure The prediction is loaded in favor of the blood Fb being the more accurate estimate since only one blood Fb is reported. From M. E. Maxfield's analysis of blood Pb determinations, a lab classed as capable of doing "precise" analyses could report, on subsequent analyses of the same sample, values varying as much as 0.02 mg Pb/100 g blood. If 0.08 mg Pb/100 g blood is a minimum effect level, that is the level at which some manifestation of interference with biological activity occurs - interference with heme synthesis - then only 17 of: the 39 specimens showed an excessive exposure to Pb. All but one of these (#23) would have been detected by the urine ALA. The question might then be whether one has more confidence in repeated ALA measurements or a single blood Fo to predict an excessive exposure. The very large swings in a given subject during the day are quite surprising and far greater than might be explained by variation in urine concentration. This needs to be resolved more than the challenge that urine ALA's frequently fail to identify persons with high blood lead levels. JRB:sfs DUP040001935 N25862.01