Applying Bioavailability Applying Bioavailability Concepts to Mine Waste Concepts to Mine Waste

CleanupsCleanups

Harry AllenHarry Allen

MSEM Project PresentationMSEM Project Presentation

Bioavailability PrinciplesBioavailability Principles

►Determine the toxicity of mine wastesDetermine the toxicity of mine wastes

►Predict public health outcomesPredict public health outcomes

►Are used to adjust treatment Are used to adjust treatment strategiesstrategies

►Case-specific exampleCase-specific example

Mine Tailings in the Mine Tailings in the EnvironmentEnvironment

Factors Determining Factors Determining BioavailabilityBioavailability

►Physical Physical Particle size and coatingParticle size and coating

►Chemical Chemical Chemical solubility and reactivityChemical solubility and reactivity

►PhysiologicalPhysiological Body’s uptake of metalsBody’s uptake of metals

►EnvironmentalEnvironmental External forces alter these properties External forces alter these properties

Physical Properties of Lead & Physical Properties of Lead & ArsenicArsenic

Lead minerals

Arsenic minerals

INCREASING BIOAVAILABILITY

Q uartz

FeAsS Quartz

Pb-Asoxides

Slag

Fe-Asoxides

Fe-Pb oxides

PbCO 3

SlagPbO

PbAsO4 Pb 0

PbO

Q uartz or S ilicate

PbCO3PbS

Measuring BioavailabilityMeasuring Bioavailability

► In-VivoIn-Vivo Swine, monkey and rat studiesSwine, monkey and rat studies

► In-VitroIn-Vitro Physiological Based Extraction TestPhysiological Based Extraction Test

Mine Waste Risk ScenariosMine Waste Risk Scenarios

W ind transfers ta ilings dust to residentia l so ilsW ind transfers sm elter em issions

to resdentia l soils (e.g. gardens)

M ine w orkers or tresspassers transm it dust and soil from w orkplace to hom e

on shoes and cloth ing

Sm elter Tailings P ile (or M ill)

R esidence

Polluntants in so ils m ay be ingested or be carried indoors as housedust

Cross contam ination by workers

Pharmacokinetic ModelingPharmacokinetic Modeling

► Is used to predict blood Pb and As Is used to predict blood Pb and As absorption in exposed communitiesabsorption in exposed communities Ex. Pb from auto emissions, house paint, Ex. Pb from auto emissions, house paint,

and active smelters show the predicted and active smelters show the predicted absorptionabsorption

►Model results do not correlate with Model results do not correlate with epidemiological studies of exposure to epidemiological studies of exposure to tailings tailings

Site Specific Risk AnalysisSite Specific Risk AnalysisRisk of exposure to 500 mg/kg arsenic in soil and 0.01 mg/m3 arsenic in air over a lifetime

Calculated Risk

Outdoor Indoor

Mining community

Ingestion 9.70E-07 1 in 1,000,000 1.90E-06 2 in 1,000,000

Inhalation 2.60E-06 3 in 1,000,000 2.60E-05 3 in 100,000

Total 3.60E-06 4 in 1,000,000 2.80E-05 3 in 100,000

Smelter community

Ingestion 9.70E-07 1 in 1,000,000 1.20E-05 1 in 100,000

Inhalation 2.60E-06 3 in 1,000,000 5.70E-05 6 in 100,000

Total 3.60E-06 4 in 1,000,000 6.90E-05 7 in 100,000

Using Bioavailability in Using Bioavailability in TreatmentTreatment

►Physical Physical Increase particle sizeIncrease particle size Coat particleCoat particle

►Chemical Chemical Change in chemical compoundChange in chemical compound

►EnvironmentalEnvironmental Create vegetative coverCreate vegetative cover Introduce organic matter (biosolids), Introduce organic matter (biosolids),

amendmentsamendments

McCleur Tailings Site

Characteristics of TailingsCharacteristics of Tailings

Tailings ATailings A

Total Lead 30,000 Total Lead 30,000 ppmppm

Total Arsenic 300 Total Arsenic 300 ppmppm

pH 2.3pH 2.3

Tailings BTailings B

Total Lead 2,000 Total Lead 2,000 ppmppm

Total Arsenic 200 Total Arsenic 200 ppmppm

pH 2.7pH 2.7

PBET ResultsPBET Results

0%

5%

10%

15%

20%

25%

Available Pb Available As

Tailings A Tailings B

High Iron Compost AdditionHigh Iron Compost AdditionReduction in Lead Reduction in Lead

AvailabilityAvailability

0%

10%

20%

30%

40%

50%

60%

Tailings A Tailings B

Reduction in Availability

TreatmentTreatment

►Remove tailings from stream channel Remove tailings from stream channel and restage aboveand restage above

►Apply biosolids and amendment Apply biosolids and amendment mixturemixture

McCleur Tailings Site: Post Treatment

McCleur Tailings Site: Post Treatment

ConclusionsConclusions

Bioavailability Technologies:Bioavailability Technologies:

►Enhance risk assessmentEnhance risk assessment►Prioritize health risks from Pb & As Prioritize health risks from Pb & As

sourcessources► Increase the cost-effectiveness of mine Increase the cost-effectiveness of mine

waste treatmentwaste treatment►Prospects for bioavailability Prospects for bioavailability