Bioavailability of soilborne lead in adults, by stable isotope dilution.
Using stable isotope dilution, we determined the bioavailability of soilborne lead (Pb) in human adult volunteers. Soil from a residential yard at a mining-impacted federal Superfund site that had negligible amounts of other priority pollutants was dried and screened through a 25-micron mesh sieve. The < 250-micron fraction, which likely represents that ingested via hand-to-mouth activity, was then sterilized by exposure to radiation. Ten replicate samples yielded a mean (SD) soil Pb concentration of 2924 +/- 36 ppm, and a mean 206Pb/207Pb ratio of 1.1083 +/- 0.0002, indicating remarkable soil homogeneity. Six adults with 206Pb/207Pb ratios of > 1.190 were admitted to the clinical research center and fasted overnight prior to dosing with 250 micrograms Pb/70 kg bw (i.e., 85.5 mg soil/70 kg) in a gelatin capsule. Blood for Pb and 206Pb/207Pb ratios was obtained at 14 time points through 30 hr. Results of the isotopic analyses from these subjects indicate that on average 26.2% +/- 8.1 of the administered dose was absorbed. Six additional subjects were subsequently studied but ingested soil immediately after a standardized breakfast. Bioavailability in this group was only 2.52% +/- 1.7. Collectively, this study provides the first experimental estimates of soil Pb absorption in humans, and should allow for more precise estimates of health risks due to Pb-contaminated soil.
Maddaloni
M
M
Columbia School of Public Health, Division of Environmental Health Sciences, New York, New York 10032, USA.
Lolacono
N
N
Manton
W
W
Blum
C
C
Drexler
J
J
Graziano
J
J
D000328:Adult; D001682:Biological Availability; D005260:Female; D006801:Humans; D007854:Lead / Q000032:analysis / Q000097:blood / Q000493:pharmacokinetics*; D007856:Lead Radioisotopes; D008297:Male; D011865:Radioisotope Dilution Technique; D012987:Soil / Q000032:analysis; D012989:Soil Pollutants / Q000032:analysis / Q000097:blood / Q000493:pharmacokinetics*
D007856:Lead Radioisotopes; D012987:Soil; D012989:Soil Pollutants; D007854:Lead