Model for Bioavailability of Heavy Metals from Landfill Soils Using Artificial Human Digestive Fluids

EPA Grant Number: GF9500062
Title: Model for Bioavailability of Heavy Metals from Landfill Soils Using Artificial Human Digestive Fluids
Investigators: Hamel, Stephanie Lynn
Institution: Rutgers University - New Brunswick
EPA Project Officer: Broadway, Virginia
Project Period: May 1, 1995 through January 1, 2000
Project Amount: $29,900
RFA: STAR Graduate Fellowships (1995) Recipients Lists
Research Category: Fellowship - Health , Health Effects , Academic Fellowships


The focus of this research is to develop a method for assessing availability of heavy metals found in hazardous soils and consequently in the human digestive system. This project seeks to establish a validated model for extraction of metals in digestive fluids to provide the necessary tool for determining the metal exposure from any soil or waste sample. Imitation biological fluids of the digestive tract are being prepared chemically, and the extraction capabilities are being examined to provide an accurate measure of the maximum amount of the metal which can cross the digestive tract membranes and be absorbed into the tissues. The experimental plan is being modified from currently used practices for pharmaceutical compounds' uptake by the gastrointestinal tract, and for nutritional studies of foods. The artificial fluids utilized in the studies sequential extraction are saliva, gastric juice and duodenal fluid, which represent the portion of the gastrointestinal tract that affects metal uptake by the body. Ingested metals are transported by saliva to the stomach where the low pH enhances metal solubility with the enzymes functioning to increase metal availability. The first region of the small intestine, the duodenum, is the site of the most metal absorption, so it is this portion of the intestine that will be modeled. Research has shown that extractability of metals is dependent on pH, with lower pH resulting in increased extraction of metals. Enzymes in the prepared bio-fluids, the soil type chosen, and the soil matrix appear to also play a role in extraction capacity. This study will focus on various time components to most accurately simulate the human system. The concentrations of various metals which are removed are analyzed, using a multi-element chemical analysis system, the inductively-coupled plasma mass spectrometer, to determine parts per billion of metals. This research has performed preliminary extractions of National Institute of Standards and Technology soils and data suggests that less than 30% of each lead, chromium, cadmium, and arsenic in a sandy soil was removed using this procedure. The model will be refined and further tested with standard soils. The data produced are preliminary and verification is needed. One aspect which must be clarified is the thermodynamic properties of the biological fluids, which may be playing a significant role in the extraction. This research will lead to an improved analytical tool for determining both the need to treat landfill waste prior to disposal into a landfill, and the availability of the metals in existing waste that potentially causes health responses in humans, due to exposure. From this work, proper recommendations will be available regarding how metals are bound to the soil, and how different conditions, including weathering of soil, the matrix and pH, affect human exposure.

Supplemental Keywords:

RFA, Scientific Discipline, Toxics, Waste, Ecosystem Protection/Environmental Exposure & Risk, Bioavailability, Chemical Engineering, Environmental Chemistry, Physiology, Chemistry, HAPS, Analytical Chemistry, Environmental Microbiology, Monitoring/Modeling, Biochemistry, Hazardous Waste, Engineering, Environmental Engineering, 33/50, Hazardous, model, landfill soils, artificial human digestive fluids, chromium & chromium compounds, cadmium & cadmium compounds, Lead Compounds, lead & lead compounds, Arsenic Compounds (inorganic including arsine), bioavailability of heavy metals from landfill soils, extraction of metals in digestive fluids, metals exposure from soil, extraction of metals in digestive fluid, Chromium Compounds, heavy metals