Document kmXn97wvqM9r55Ye816RpRXeV

> NHANES II Blood-Lead Data Correlation With Air-Lead Concentration Data The data analysis presented by "Ethyl Corporation's Comments Following EPA's Public Hearing on Proposed Rule for Lead in Gasoline" submitted October 8, 1982 used population density as a correlating variable for blood lead. Population density was suggested as representative of the local air-lead exposure. Air-lead concentration data are available for 24 of the locations for the quarter in which the blood-lead sampling occurred from air sampling reported by the National Air Sampling Network. The blood-lead contributions as described in the October 8, 1982 submission have been correlated with the independent variables of time (T), the logarithm of the population density (P), and the air lead concentration (A). Table 1 lists the variables. The results of the linear regression with this three-constant model are: Independent Variable T P .A t 57W 0.63 1.27 S * 0.0948 for this correlation, t is the absolute value of the "Students t" and S is the residual squared error. Results of the linear regression with time and either population density or air lead concentration as independent variables gives the following: Independent Variables iXi....................X2 t Xi. Xa S' TP TA 5.27 5.14 1.41 1.84 0.0962 0.0935 The correlation with T and A shows a lower residual squared error than the correlation with T and P or with the three variables T, P, and A. Thus correlation with time and the air lead concentration provides the "best fit" of the blood-lead contributions. The resulting correlation equation is: Blood lead contribution ** 2.925 - 0.0002197T + 0.0777A (1) Correlation of the blood lead contribution with the single variable A gives a correlation coefficient {r) of 0.21 adjusted for the degrees of freedom and S - 0,1372, t(a) * 1.45. Thus air lead concentration without time as a variable does not provide a statistically significant representation of the,data. N33864 TEH 0533021 r \ .2 The blood lead contribution for each location is essentially the natural logarithm of the mean blood lead for the location. Equation 1 with T in the range of that for the data sampling shows blood-lead response to air-lead in the range of 1.0 to 1,5 yg/100 ml per yg/m3 which is consistent with reported values for this ratio. Equation l also shows that incremental air lead from zero to 1 yg/m3 represents 7.5% of the blood lead contribution. Correlation of the NHANES II data with the corresponding air lead concentrations show that the assumption of population density to represent local air lead exposure is a good assumption. As gasoline lead is transmitted by air movement and is respired into the lungs with absorption into the blood, air-lead concentration would be expected to be the variable that represents, gasoline lead contribution to blood lead. This is observed to be I about 7.5% for the air-lead increment of zero to one yg/m3. GAH:jtd Attachment 1-18-83 G, A. Hughmark TEH 0533022 DUP050034292 , ...I* - / TABLE 1 Data Summary vocation ID No, 3 5 6 9 11 12 13 20 21 24 25 28 30 31 33 36 37 38 43 52 55 57 58 63 Blood-Lead Contribution* 2.89 2.92 2.93 2.90 2.76 2.67 3,08 2.84 3,08 2,63 2.91 2,74 2.54 2.78 2.58 2.88 2.82 3.06 2.80 2.86 2.82 2.86 2.77 2,75 Sample Time+ 111 -151 882 237 268 1321 284 1062 522 1326 665 1127 1361 1261 1421 105 707 143 934 535 605 1064 663 1262 Air-Lead Concentration im/m3 0.82 0,32 0.43 1.18 0.69 0.46 1.18 0.95 1.84 0,58 1.05 1.21 0.14 0,50 1.45 1,05 1.60 0.54 0.49 0.99 0.46 1.63 0.40 0.96 Populate Densitv no./mia 257 2091 352 497 1691 1293 5734 1338 3805 95 543 1131 263 1997 11643 70 1593 247 509 5217 223 1269 328 2189 * Averaged mean blood-lead contribution for each location, + Weighted average sample time (days) from January 1, 1976. TEH 0533023 DUP050034293