The Bioavailability of Soil Lead.* M. W. Kierski, WARZYN, One Science Court, Madison, WI 53705; and J. B. Stevens, RUST Environment & Infrastructure, 3033 Campus Drive, Minneapolis, MN 55441
The relative oral bioavailability of soil-lead was investigated in this study by comparing the bone-lead concentrations of rabbits fed a reference lead compound, lead acetate (PbAc), to animals fed equidoses of lead present in contaminated roadside soil. A thirty day feeding regimen was employed using weanling New Zealand white rabbits. Lead bioavailability was evaluated over a dose range of 0.75-7.5 mg/kg-b.w. The relationships between soil characteristics, dose parameters (lead and soil) and metal bioavailability were all determined. It was found that under the conditions of this experiment, the oral bioavailability of soil-lead was independent of (a) the organic matter content of the soil, (b) the lead binding capacity of the soil, and c) the concentration of lead in the soil. Beneath a threshold dose, lead bioavailability was also found to be independent of the amount of soil administered. However, soil-lead bioavailability was found to be inversely related to the acid buffering capacity of the soil. Since the bioavailability of soil-lead at low soil doses was shown to be similar in magnitude to the oral bioavailability of lead acetate, it was concluded that soil-lead should be considered equally bioavailable as soluble lead for risk assessment purposes. A similar conclusion may also be valid for other inorganic metals in soil.
*Work supported by the Minnesota Department of Health.