Impact of Diet on Pb Bioccessibility for Wildlife in Vitro Methods.

Human activities have introduced Pb into the environment, posing a risk to both humans and wildlife. To determine the risk of Pb exposure to wildlife, ecological risk assessment is used. Currently, risk assessment relies on the assumption that lead exposure results in complete absorption, i.e. 100% relative bioavailability. This is often inaccurate, as bioavailability decreases depending on the media with which Pb is consumed. Not knowing bioavailability can lead to overestimation of exposure, impacting risk assessment and making reclamation efforts more expensive. In vitro methods are used to characterize human bioavailability for Pb in soil, and could be used to estimate bioavailability for wildlife. Since the Pb exposure pathway for wildlife is through feeding, in vitro methods for wildlife need to measure bioavailability of Pb in diet rather than soil. In this study, 4 in vitro methods that have been found to accurately predict bioavailable Pb for Japanese quail (Courtnix japonica) were further tested to see if they would detect changes in bioaccessible Pb in six different diets spiked with lead acetate. Diet was found to significantly impact bioaccessibility, and the effects varied both with in vitro method and with diet. Reductions up to 50% were observed in some diets and methods, while increases in bioaccessibility up to 2250% occurred in others. Diet phosphorus appeared to be inversely correlated with bioaccessible Pb for one method. However, method pH and calcium, fiber, and phytate content were not strongly correlated with changes in Pb solubility for any method, indicating complex interactions between Pb and dietary components. Further research is needed to find which dietary components impact bioavailability, and if diet-related changes in bioaccessibility are seen in bioavailability in animal models. Once correlated with animal models, in vitro methods can quickly and inexpensively estimate bioavailability of contaminated diets for ecological risk assessment.