Document 2Na7o5MpQO7VkdayOvnYaLoKL

:-r ,* 'EN-1136-A Rev. 5/28/81 ESP CLEARANCE OF TECHNICAL RELEASES (Including Speeches 6 Publications) Date Initiated: 5/27/83 Pate Approval Necessary: Pate of Release, Presentation, or Publication: 9/6/83 Title: ASSESSMENT OF BLOOD LEAD LEVELS IN THE U.S.A. FROM NHANES II DATA Author (a): 'J. M. PIERRARD (C&P DEPT.), CHARLES G. PFEIFER, RONALD D. SNEE . INTERNATIONAL CONFERENCE ON HEAVY METALS IN THE For Release/Presentation to: ENVIRONMENT, HEIDELBERG, NEST GERMANY For Publication in: PROCEEDINGS feF CONFERENCE Approval Oral Release on* publication Oral with Preprint 80010ral Publicatlon thar (DMCribe UHder Name ROOTING SEQUENCE FOR CLEARANCE Approval: Initials/Pate D. W, MARQPARDT Genl.review - Regl.Office Mgr, if applic. For technical accuracy, grammar (Cons.Mgr Other ESD staff at discretion of Cons.Serv.Mgr./Field Engg.Mgr. 3 Responsibilities/Opinions of Consultant Services Manager/Field Enggr. Manager .1 Release dees/does -not relate to specific Company processes or products. Indus, dept, clearance iwabosneceesaxy/has been obtained from . ____________ , Pos. , Dept. C&P (SEE REMARKS) 2 Release does/does not contain potentially patentable material. * 3. Release does/idostsxttttfc: state, infer, or refer to Company policy. Public Affairs clearance not 4. Legal Department clearance not 5. Release should be cleared with other departments before issuance (generally Research Dirs., including ERDD): a) for information* ) b) for approval* ') check one . c) not necessary ") 8 Competitive advantage of release of information is/is not minor relative to benefits of release. N/A /l/t l// / 7, Approval by Cons > Serv. Mgr. /Field Engg.Mgr.-overall responsibility fj]L J UShi P. V, Tebo, ESP Speech/Paper Coordinator - final approval Remarks: WORK DONE FOR PETROLEUM CHEMICALS DIVISION, C&P, WHICH HAS RESPONSIBILITY FOR CORPORATE CLEARANCE. PUBLICATION WILL BE SUBMITTED TO CONFERENCE BY THE C&P AUTHOR. *Can be Field staff or direct contact' in indus./staff dept, +ESD Speech/Paper Coordinator will handle this (maintains list of contacts). N33821 TEH 0532464 ASSESSMENT OF BLOOD LEAD LEVELS IN THE TJ.S.A. FROM NHANESII DATA John M Pierrafd*, Charles G Pfeifer+ and Ronald D Snee+ ABSTRACT Changing demographics of the subject groups at the 64 sites sampled dur ing NHANESII accounts for over half the apparent 5.61 ug/dl blood lead decrease from 1976 to 1980. Site-specific gasoline lead exposure accounts for 0.51 ug/dl of the blood lead decrease, in agreement with the change expected due to the decrease of 0.32 ug/m3 in average air lead and the accepted range 1 ^ < 2 for blood lead response to air lead change, INTRODUCTION The U.S. Government's second National Health and Nutritional Examination Survey (NHANESII) was a cross-sectional study designed to assess national health status. Venous blood lead levels (BPb) were measured for 9,936 of the 20,333 examinees. Mobile caravan teams visited 64 sites in the contlnguous U.S.A. and Hawaii between 1976 and 1980, A preliminary analysis reported a 36.7% reduction in BPb over the four-year study period and noted that the decrease in BPb reflects the decrease in national use of lead in gasoline production (ref 1). Because the NHANESII sample was not selected to insure valid within-study time analyses, several categories of demographic variables were evaluated in the present study to examine their effect on the reported BPb decline. Three alternative measures of exposure to lead from gasoline were tested for their utility as indicators of BPb response. Finally, time was intro duced to represent all other time-related BPb effects that may be present. ADJUSTMENT FOR DEMOGRAPHICS The effect of changing site demographics on the BPb time trend was inves tigated by classifying each examinee in terms of 6 personal variables (P) describing race, sex, age and family income, 3 residence variables (R) describing degree of urbanization, and 6 caravan itinerary variables (1) describing season of the year and region of the U.S.A. These classifica tion variables assume a value of 1 if the descriptor applies to the exam inee, 0 otherwise. Means were computed for each site based on examinee records with a venous BPb, and the 64 site means further analyzed. Three BPb adjustments were evaluated corresponding to different selection sets of candidate explanatory terms for variation among site mean BPb's. The first set included the 6 P variables and their 15 two-way interactions; the second set added the 3 R variables to the first set; and, the third set added the 6 1 variables to the second set. A weighted least squares stepwise regression procedure was applied to each full set of selection candidates. Weighting was by number of BPb values at each site. *E. I. du Pont de Nemours & Co., Inc., Wilmington, DE, USA, Petroleum Laboratory, + Engineering Department TEH 0532465 DUP050033730 tends were retained if their significance with BPb satisfied the p <0.15 criterion. Adjusted site mean BPb's were obtained by adding the weighted site mean BPb to the residuals from the final regression model. Each adjusted set of values, along with the unadjusted BPb's, then was regressed on site mean examination date. Values of BPb were predicted at the first and last site mean examination date in NHANESII to evaluate the influence of dif ferential site demographics. the results of the time analyses on the unadjusted and adjusted site mean BPb's are given in Table 1. they illustrate the confounding inherent among BPb, site demographics and time during the study period. Each group of demographic variables was able to explain some of the time trend with terms from the third selection set reducing the unadjusted decrease by more than half. Table 1 Time Trend and Pour Year Change of Blood Lead Unadjusted and Adjusted for Demographics Unadjusted Adjusted for P for P and R for P, R and I Time Trend Std. ug/dl/yr Error -1.43 0.18 -1.09 -0.74 -0,57 0.18 0.17 0,14 Remaining Four Year Decrease BPb, ug/dl % 5.61 32,7 4.29 2.92 2.26 26,0 18.4 14,5 ADJUSTMENT FOR GASOLINE LEAD AND DEMOGRAPHICS Gasoline lead (GPb) is the best documented of the Identified sources lead which include food, water, paint and dust. National GPb use has been claimed to explain the decrease in unadjusted BPb (ref 2), and so was eva luated as one GPb exposure variable. National GPb use (tonnes) was com puted from data by state on lead content and consumption of gasoline. To reflect site to site variation, a GPb density (tonnes/mi*) for each site was computed by multiplying the relevant state GP use by the ratio of population in the site counties to state population, and dividing by land area of the site counties, The basis for this definition is the correla tion between population and gasoline use (ref 3). Subsite GPb density was calculated similarly but based on each BPb examinee's residence char acteristics, Applicable data permitted calculation of all 3 GPb exposures for 55 of the original 64 sites. Mean BPb's from the 55 sites were adjusted as before for 5 selection sets, each containing all of the P,R and 1 demographic terms and one of the GPb exposure variables or its logarithm. The adjusted BPb's then were regres sed on site mean examination date. These results, along with the signifi cance levels of the GPb exposure terms, are given in Table 2. In all cases inclusion of a GPb term further reduced the BPb decrease from the 2.26 ug/dl unaccounted for by demographics. The remaining trend was con sistent for all but national GPb use. TEH 0532466 DUP050033731 Table 2 Time Trend and Four Year Change of Blood Lead Adjusted for Demographies and Gasoline Lead Exposure GPb Exposure Variable Signif* Level 9 Rational 0.0001 Site Density 0.0001 Subsite Density 0.0311 Log (Site Density) 0.0001 Log (Subsite Density) 0.1076 Time Trend Std. ug/dl/yr Error -0.14 -0.44 -0,47 -0.52 -0,39 0.12 0.13 0,12 0.13 0.13 Remaining Four Year Decrease BPb, ug/dl % 0.57 1.75 1.85 2.05 1.55 3,8 11.3 11.9 13.1 10,1 TIME-RELATED BLOOD LEAD EFFECTS In the absence of credible and suitable data on lead sources besides gaso line, a time variable, reflecting site mean examination date, was adopted as a surrogate for other time-related BPb effects. A stepwise regression procedure was used on each of 5 selection sets again containing the full set of demographic terms, one of the GPb exposure variables and the sur rogate, time. First, the model was forced to include both time and the GPb variable used; in companion analyses the selection of all terms was allowed to proceed solely on the basis of the inclusion criterion. As shown in Table 3, under both forced and unforced conditions the time vari able was significant for all cases, but only Site GPb Density retained significance. When time is taken into account as a surrogate for un quantified time-related BPb effects, national GPb use is no longer signi ficant. These results suggest other time-related BPb effects are present in NHANESII. Table 3 Significance Levels of Gasoline Lead Exposure and Time Terms in Models Including Demographics Forced Unforced GPb Exposure. Variable GPb Signif. Level Time Signif, Level GPb Signif, Level Time Signif, Level National Site Density Subsite Density Log (Site Density) Log {Subsite Density) 0.8850 0.0022 0.6276 0.0019 0.7520 0.Q001 0.0001 0,0001 0.0001 0.0001 NS 0.0022 NS 0.0019 NS 0.0001 0,0001 0,0001 0.0001 0.0001 NS Not Selected, p> 0.15 TEH 0532467 DUP050033732 CONCLUSIONS This analysis has shown that many factors related to personal and resi dence characteristics and sampling itinerary significantly affect NHANESII BPb values, and can account for 3.35 ug/dl of the apparent decrease be tween 1976 and 1980. Of the GPb exposure variables only Site GPb Density and its logarithm had a significant effect on BPb in the presence of the time surrogate. The portion of the four-year decrease due to Site GPb Density was determined by the analysis to be 0.5 ug/dl. This is consis tent with the observed national average air lead decrease pf 0.3 ug/m3 over the same period (ref 4), and the well-documented air lead/blood lead relationship (ref 5,6). Figure 1 shows the relative contributions to the four-year blood lead decrease. The unexplained portion of the BPb decrease, 1,75 ug/ dl, is reflected by the time variable and may be due to improved sample handling over the course of the NHANESII study, effectiveness of numerous government programs to reduce lead intake through food, paint and water (ref 7), or other unquanti fied causes. REFERENCES 1. Centers for Disease Control, Morbidity and Morality Weekly Rep 30, 132 (1982) 2. New Scientist, 94, 570 (1982) 3. J M Pierrard et al, Vehicle Emissions Controls and Ambient Air Quality, SAE Australasia, Jubilee Year Conference, Melbourne (1977) 4. EPA Office of Air Quality Standards, National Trend in the Maximum Quarterly Average Lead Levels, 1970-1979 5. R D Snee, Inr. Arch Occup Environ Health 48, 219 (1981) 6. W Sinn, Int Arch Occup Environ Health 47, 93 (1980) and 48, (1981) 7. National Academy pf Sciences, Lead in the Human Environment Washington, D,C. 1980) p. 477 TEH 0532468 DUP050033733