The estimation of bioaccessibility of heavy metals in soils using artificial biofluids

Bioaccessibility, the maximal amount of metal that is soluble in synthetic gastrointestinal fluids, has been shown to estimate human exposure to heavy metals in soils. A synthetic model was created, to provide an approximation of fluids in human gastrointestinal system. The protocol predicts the fraction of contaminant that is extractable in human biofluids and thus is available for uptake across the gastrointestinal tract lining.; A mass-balance protocol was developed to chronicle the amount of metal dissolved in each of the fluids of the bioaccessibility extraction protocol, and to measure the amount of metals remaining in the soil. The mass-balance protocol accounts for the lead in Montana Standard Reference Material 2710 and for lead and chromium in slag material collected from Jersey City, NJ. Other soils used in this study did not show a 100 {dollar}pm{dollar} 20% metal recovery, so the mass-balance technique needs to be refined. This difficulty implies that a protocol needs to be developed to obtain {dollar}rm Msb{lcub}TSigma{rcub},{dollar} metal mass total as the sum of the metal masses, equal to {dollar}rm Msb{lcub}T3051{rcub},{dollar} the concentrated acid extractable total mass. The bioaccessible fraction can be determined using the {dollar}rm Msb{lcub}TSigma{rcub}{dollar} value.; The bioaccessibility of heavy metals in soils varies with soil type. In four soils materials examined, the bioaccessibility of lead ranged from 39% to 70% of total metal. Arsenic in the residential soil was 41% bioaccessible, the chromium in Jersey City slags material: 34%. The bioaccessible fractions were less than the total metal concentration in soil, estimated by acid extraction techniques. For soil collected from Bunker Hill, ID, which was fed to human subjects in another study, bioaccessibility proved to be greater than human bioavailability: bioavailability {dollar}<{dollar} bioaccessibility {dollar}<{dollar} total metal mass.; The use of the bioinaccessible fraction as an indicator of bioaccessibility will allow for an adequate estimation of bioaccessibility while minimizing laboratory efforts.; The Integrated Exposure Uptake Biokinetic Model calculations, using the data obtained in these bioaccessibility experiments, predicted lowered lead levels in children, compared to the estimates using total soil metal concentration.