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Comparing the relative bioavailability (RBA) of lead (Pb) in soil and dust
Citation:
Thomas, D., B. Elek, C. Nelson, AND K. Bradham. Comparing the relative bioavailability (RBA) of lead (Pb) in soil and dust. Society of Toxicology, Baltimore, Maryland, March 10 - 14, 2019.
Impact/Purpose:
This is an abstract for a presentation at the 2019 annual meeting of the Society of Toxicology which will be held March 10-14, in Baltimore, Maryland.
Description:
Soil and dust are the predominant sources of Pb exposure for children in the United States. Although quantitation of the intake of Pb from soil and dust ingestion is problematic, the importance of these sources is emphasized by studies that show that reducing levels of Pb in soil and dust lowers blood Pb levels in children. Here, we have used a mouse assay to estimate the RBA for Pb in urban soil and dust. These studies used NIST Standard Reference Materials (SRM) with certified mass fraction values for Pb as test materials. SRMs tested were 2584 (indoor dust), 2587 (soil containing Pb from paint), and 2710a (Montana I soil). Pb acetate (PbAc) was used as a source of highly soluble Pb. The test materials were used to amend AIN-93G rodent diet that was consumed by adult female C57BL/6 mice in an established assay for estimation of Pb bioavailability. Final levels of Pb in test diets ranged from about 3 to 30 parts per million. RBA estimates for Pb in different test materials were derived from linear regression analysis of the relation between cumulative Pb intake from amended diet and the concentration of Pb in skeleton or blood, two tissue biomarkers of Pb exposure. For blood, the rank order of slopes of regression lines from highest to lowest was 2584 > PbAc > 2587=2710a. For skeleton, the rank order of slopes of regression lines from highest to lowest was PbAc > 2584 > 2587 > 2710a. Thus, the rank order of RBA estimates derived from blood is 2584 > 2587 = 2710a. The rank order of RBA estimates derived from skeleton is 2584 > 2587 > 2710a. Differences in the RBA for Pb in different soil and dust samples may reflect differences in the speciation of Pb present in these materials or modifying effects of constituents that are present in some environmental media. Continuing studies of matched soil and dust samples collected from individual homes will provide new insights into the relation between sample composition, Pb speciation, and bioavailability. (This abstract does not reflect U.S. EPA policy.)