STABLE-ISOTOPE IDENTIFICATION OF LEAD SOURCES IN PRESCHOOL-CHILDREN - THE OMAHA STUDY

The objective was to determine, from analysis of the naturally occurring stable isotopes of lead, the relative contribution of food, handdust, housedust, soil and air lead to the absorbed (urinary) lead and the blood lend of children living in a former smelter city. A longitudinal 12 month study was conducted of 21 children, 2 - 3 years of age, living in central Omaha, balanced for race, gender and socioeconomic status. Field clean samples were collected monthly of 24 hour duplicate diet, handwipe and urine, with quarterly blood lead, annual environmental lead, weekly air for total lead and Pb-206, Pb-207 and Pb-208 by thermal ionization/mass spectrometry with a Pb-205 spike in a Class II laboratory. Despite residence in a smelter city each child had a unique isotopic ratio of handwipe, blood and urine lend, the latter being identical. There was no correlation of handwipe isotopic ratio with proximity to a lend emission source or to the decade of the housing stock. The isotopic ratio of the annual mean handwipe lead predicted 43% of the variance of the annual mean blood and urine lead ratio (r(2) = .43, p = .001). Handwipe lend ratios correlated (p less than or equal to .05) with those of the windowsills and air ducts. The mean isotopic ratios of brood mid urine lend were lower than those of handwipe and food, consistent with a contribution by endogenous bone lend. Clean catch urine provides a noninvasive index of blood lead isotopic ratio in children, as in adults.