DEVELOPMENT OF AN IN-VITRO SCREENING-TEST TO EVALUATE THE IN-VIVO BIOACCESSIBILITY OF INGESTED MINE-WASTE LEAD

A screening-level in vitro test was developed to evaluate the relative solubility of ingested lead (Pb) from different mine wastes in the ga strointestinal (GI) tract. The in vitro method, modeled after assay me thods for available iron from food, used a laboratory digestion proced ure designed to reproduce GI tract chemistry and function. The in vitr o method was independently calibrated against a rabbit feeding study, demonstrating that only 1-6 % of the total Pb in four mine-waste sampl es with disparate Pb mineralogy was bioaccessible. In vitro method dev elopment tests indicated that H+ concentration and Cl- complexation co ntrol dissolution of Pb-bearing minerals in the stomach and that both GI tract enzymes and organic acids are necessary to maintain Pb in the soluble form on entering the small intestine. The experimental result s indicate that ingestion of Pb-bearing mine wastes results in limited Pb solubility and that the in vitro test provides a screening-level e stimate of the maximum available Pb from mine wastes.