Bioavailability of soilborne lead in adults, by stable isotope dilution.

Abstract

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-pm mesh sieve. The <250-pm 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 pg Pb/70 kg bw (i.e., 85.5 mg soilf70 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.

Comparison of five in vitro digestion models to in vivo experimental results: Lead bioaccessibility in the human gastrointestinal tract

“…Significant differences (p=0.0008) between all methods, including the in 4 vivo study by Maddaloni et al (1998) [8] , were obtained. The bioaccessibility values from all 5 small intestinal digestions were higher than the in vivo bioavailability results (Figure 3).…”

“…The amount of soil and the meal was based on the study presented by Maddaloni et al [8] . One 8 hundred milligrams of soil were introduced in the model with 240 mL of water or the standard 9 breakfast from the in vivo study to study the fasted and fed situation, respectively.…”

“…method was applied to separate the bioaccessible from the non-bioaccessible fraction: 3000 g 6 centrifugation (RIVM method), 7000 g centrifugation (SHIME and DIN), microfiltration 7 (PBET) and dialysis (TIM). As the separation method will largely influence which fraction of 8 the solubilized lead is considered as bioaccessible, the RIVM performed additional tests on 9 the Bunker Hill soil under fed conditions with the same breakfast formulation as the one used 10 in the in vivo study from Maddaloni et al (1998) [8] and that used with the TIM model. As 11 expected, it was found that the bioaccessibility was largely influenced by the separation 12 method with 3000 g centrifugation yielding the highest bioaccessibility value (31.5%), 13 followed by microfiltration (22%) and dialysis (3.5%) ( Table 2).…”

Lead isotope ratio measurements as indicators for the source of lead poisoning in Mute swans (Cygnus olor) wintering in Puck Bay (northern Poland)

“…As a result of this, the isotopes and their ratios (between themselves, including the 204 isotope) may be applied to the recognition of the Pb ore which was used to produce the material (Scheuhammer and Templeton, 1998;Scheuhammer et al, 2003;Thomas et al, 2009). Knowing these isotopic ratios in various materials, it is possible to compare them with values found in biological samples to recognize the possible pollutant connection (Maddaloni et al, 1998;Scheuhammer et al, 2003;Svanberg et al, 2006).…”

Influence of environmental zinc on the association between environmental and biological measures of lead in children

“…In addition to having more opportunities for oral exposure to contaminated dust and soil, children may absorb a greater proportion of ingested lead than adults (ATSDR, 1999). A study of adults residing near a National Priorities List (NPL) site indicated that the bioavailability of ingested soil-borne lead in adults was approximately 26% (Maddaloni et al, 1998). Based on lead absorption studies, the predicted bioavailability of ingested soil-borne lead in children ranged from 25% to 41% (Ziegler et al, 1978;Casteel et al, 1997;ATSDR, 1999).…”