Bioaccessibility studies using in

Transcription

1 Bioaccessibility studies using in vitro extraction methods on soils of North America Suzette A. Morman, RN, MSc., MPH (303) David B. Smith, PhD (303) U.S. Department of the Interior U.S. Geological Survey

2 The Challenge Anthropogenic versus Geogenic

3 The Challenge For Particulate Matter Research (PM) Anthropogenic Human impact on the environment (e.g., chemicals, pesticides, id energy production, and mining) Geogenic produced from the Earth by natural processes ( e.g., volcanic ash, windborne ash from wildfires, and mineral dusts) Geoanthropogenic - produced from natural sources by processes that are modified or enhanced by human activities, e.g., dusts from lakebeds dried by human removal of water) Aral Sea p?id=39944

4 The Challenge Geogenic or naturally occurring earth materials such as soils, dusts and ash may contain known or potential toxicants. Exposure levels needed to trigger disease and causal links to disease are lacking for many materials

5 The Challenge Occupational exposures Single element or mixture Concentration Route of Exposure Duration of Exposure Environmental exposures Element mixture (metals) Concentration Route of Exposure Duration of Exposure Matrix composition and effects

6 The Challenge Particle Characteristics of Toxicological Interest Particle mineralogy Particle size distribution Particle morphology Chemical composition (bulk, and of different phases) Particle biosolubility, bilit bioreactivity, it bioaccessibility along inhalation, ingestion exposure pathways

7 In Vitro Bioaccessibility Tests (IVBA) Bioaccessibility The amount of a toxicant that is soluble in simulated body fluid and available for uptake. IVBA s measure bioaccessibility in simulated body fluids (% Bioaccess. = (conc. leachate/total t l conc.)* 100) Fast & Inexpensive Gastric (ph 1.5) Gastric to Intestinal Lung (ph 7.4) Phagolysosomal (ph 4.5) Linked to detailed mineralogical, physical characterization of test materials

8 IVBA

9 The North American Soil Geochemical Landscapes Project. Examine size fraction (<2mm or <250µm) and variations/controls in/on bioaccessibility N-S transect Randomly selected 0 5 cm soil Split, half sieved to <2mm and half to <250µm Simulated gastric leach (ph 1.5, temperature 37 for 1 hour) (Morman et al Applied Geochemistry, v. 24 8)

10 Results - Total Chemistry (mg/kg) Both Transects As Cd Cr Ni Pb Max Min <1 < Median N-S Transect Max Min <1 < Median Selected Samples Max Min 1 < Median

11 Results No significant difference in median concentration values between size fractions for total chemistry or % bioaccessibility. Regression analysis showed no correlation with several controls on mobility (soil ph, clay content, organic C,) Cd, Ni and Pb demonstrated weak correlation to total concentration % Bioacces ssibility Cd (<2 mm) µm) Cd (<250 m) Pb (<2 m Pb (<250 µm) Ni (<2 mm m) Ni (<250 µm) m) As (<2 m As (<250 µm) m) Cr (<2 m Cr (<250 µm)

12 Arsenic % 5% As <2 mm (total, mg/kg) % 7% As <2 mm (mg leached/ kg solid) mg g/kg % 10% 2% 4% As <250 µm (total, mg/kg) 2.00 As <250 µm (mg leached/ kg solid) 5% PH PH 32-4-PH 31-2d-1-PH 30-1-PH 29-3d-1-PH PH PH 024-3d-PH PH

13 Arsenic Morman S et al 2008 Geological Societ of America Meeting Morman,S., et al, 2008, Geological Society of America Meeting abstracts with Program, Vol. 40, No. 6, p78

14 Cadmium mg/k kg % 104% 58% 54% 68% 61% 55% 57% 58%60% 71% 57% 59% 66% Cd <2 mm (total, mg/kg) Cd <2 mm (mg leached/ kg solid) % 65% 66% 55% 86% 44% Cd <250 µm (total, mg/kg) 0.05 Cd <250 µm (mg leached/ kg solid) 0.00

15 Chromium % 2% 2% 2% 1% 1% 1% Cr <2 mm (total, mg/kg) % 1% 04% 0.4% 0.7% 0.3% Cr <2 mm (mg leached/ kg solid) mg/k kg % % 2% 3% Cr <250 µm (total, mg/kg) Cr <250 µm (mg leached/ kg solid) PH PH 32-4-PH 31-2d-1-PH 30-1-PH 29-3d-1-PH PH PH 024-3d-PH PH

16 Interferences on Cr Values Cr measured at 52 Cr or 53 Cr Using normal quadrupole ICP-MS false positives can result due to interferences at these masses from 40 Ar 12 C and 37 Cl 16 O which are formed in the plasma Use of Dynamic Reaction Cell (DRC) ICP-MS with NH 3 as the reaction gas can eliminate these interferences giving an accurate concentration for Cr background levels in the fluids NH 3 at 0.9 and RPq at 0.65 Both solutions were run in both modes during the same analysis Cr Concentration Normal Q-ICP-MS DRC-ICP-MS Lung Fluid Blank 110 ppb 0.9 ppb Gastric Fluid Blank 92 ppb 1.5 ppb

17 Nickel % 16% Ni <2 mm (total, mg/kg) 15% 19% mg/k kg % 24% 9% 25% 23% 9% 15% 13% 13% 14% 9% Ni <2 mm (mg leached/ kg solid) Ni <250 µm (total, mg/kg) % 34% 15% % 4% Ni <250 µm (mg leached/ kg solid) PH PH 32-4-PH 31-2d-1-PH 30-1-PH 29-3d-1-PH PH PH 024-3d-PH PH

18 Lead % 10% 28% 26% 23% 18% 14% 22% 16% 45% 21% 24% 44% 44% Pb <2 mm (total, mg/kg) Pb <2 mm (mg leached/ kg solid) mg/ /kg % 19% 16% 25% 29% 17% Pb <250 µm (total, mg/kg) Pb <250 µm (mg leached/ kg solid) PH PH 32-4-PH 31-2d-1-PH 30-1-PH 29-3d-1-PH PH PH 024-3d-PH PH

19 Conclusions No significant difference between soil size fractions for metals examined No strong correlations with usual controls on element mobility in soils IVBA s are a useful tool within context - particle characteristics, source apportionment etc.

20 Thanks Geoff Plumlee Paul Lamothe Ruth Wolf Geoff Plumlee, Paul Lamothe, Ruth Wolf and Monique Adams