Bioaccessibility tests accurately estimate bioavailability of lead to quail

Abstract

Hazards of soil-borne lead (Pb) to wild birds may be more accurately quantified if the bioavailability of that Pb is known. To better understand the bioavailability of Pb to birds, the authors measured blood Pb concentrations in Japanese quail (Coturnix japonica) fed diets containing Pb-contaminated soils. Relative bioavailabilities were expressed by comparison with blood Pb concentrations in quail fed a Pb acetate reference diet. Diets containing soil from 5 Pb-contaminated Superfund sites had relative bioavailabilities from 33% to 63%, with a mean of approximately 50%. Treatment of 2 of the soils with phosphorus (P) significantly reduced the bioavailability of Pb. Bioaccessibility of Pb in the test soils was then measured in 6 in vitro tests and regressed on bioavailability: the relative bioavailability leaching procedure at pH 1.5, the same test conducted at pH 2.5, the Ohio State University in vitro gastrointestinal method, the urban soil bioaccessible lead test, the modified physiologically based extraction test, and the waterfowl physiologically based extraction test. All regressions had positive slopes. Based on criteria of slope and coefficient of determination, the relative bioavailability leaching procedure at pH 2.5 and Ohio State University in vitro gastrointestinal tests performed very well. Speciation by X-ray absorption spectroscopy demonstrated that, on average, most of the Pb in the sampled soils was sorbed to minerals (30%), bound to organic matter (24%), or present as Pb sulfate (18%). Additional Pb was associated with P (chloropyromorphite, hydroxypyromorphite, and tertiary Pb phosphate) and with Pb carbonates, leadhillite (a lead sulfate carbonate hydroxide), and Pb sulfide. The formation of chloropyromorphite reduced the bioavailability of Pb, and the amendment of Pb-contaminated soils with P may be a thermodynamically favored means to sequester Pb. Environ Toxicol Chem 2016;35:2311-2319. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US Government work and, as such, is in the public domain in the United States of America.

Mapping the spatio-temporal risk of lead exposure in apex species for more effective mitigation

“…directly through high soil Pb levels and/ or indirectly through enhancing lead solubility at low soil pH values [24]) as the main source for background (or environmental) lead levels in griffon vultures in our study area (figures 1 and 2). Vultures can indirectly ingest lead biologically incorporated by the large grazing animals they scavenge [11,12].…”

Revisiting the Avian Eco‐SSL for Lead: Recommendations for Revision

“…This is important because the absorption of Pb depends not only on the source of the Pb but also on chemical constituents of the diet and on any soil present in the gut (Chaney et al ). For example, the bioavailability of lead acetate was reduced by 47% with the addition of 5% soil to a rat diet (Chaney et al ) and by 27% with the addition 4% soil to a Japanese quail diet (Beyer et al ). To adjust for the bioavailability of soil Pb, we rely on a study in which Japanese quail were fed a maintenance game bird chow amended with 4% soil collected from each of 5 Pb‐contaminated Superfund sites.…”

“…To adjust for the bioavailability of soil Pb, we rely on a study in which Japanese quail were fed a maintenance game bird chow amended with 4% soil collected from each of 5 Pb‐contaminated Superfund sites. The mean relative bioavailability reported for the 5 sites was about 50% (mean = 49.4%, range of 33% to 63%; Beyer et al ), which we use in our calculations. We have not accounted for the bioavailability of Pb in the soil‐free diet.…”

“…The dietary exposure model was iteratively solved using the Goal‐Seek function in Microsoft Excel to identify the soil Pb concentration that resulted in an exposure estimate equivalent to the ED10, ED20, and ED50 values derived based on dose–response analysis. This process was repeated for all 4 receptor species, assuming relative bioavailability of Pb in soil to be either 100% (to be consistent with the original Eco‐SSL) or 50%, which is representative of the bioavailabilities determined for soils from sites contaminated by mining and smelting (Beyer et al ).…”

Use of Amendments to Restore Ecosystem Function to Metal Mining-Impacted Sites: Tools to Evaluate Efficacy

“…The PBET procedure was initially developed to predict the portion of total Pb in soils that would become soluble and is absorbed in the human gastrointestinal system, but versions of this extract have also been developed to predict metal toxicity to waterfowl [32,63,64] and terrestrial birds [65]. It is important to note that much better correlation of bioaccessibility with mammalian bioavailability was demonstrated for pH 2.5 than the EPA set pH 1.5 for this extraction [32].…”