Environmental Engineering Reference
In-Depth Information
pigs. (Juhasz. et. al.. 2007),.cattle. (Bruce. et. al.. 2003),. monkeys.(Freeman. et. al..
1995),.humans.(Ziegler.et.al..1978),.and.more.typically.guinea.pigs.or.rabbits.
(Freeman. et. al.. 1993).. As. part. of. an. environmental. health. risk. assessment.
of.metals.(including.lead.and.arsenic).in.a.residential.area.in.Canberra.(Ng.
et.al..1998),.arsenic.contamination.at.dip.sites,.and.copper.chrome.arsenate-
contaminated. site. in. NSW. (Ng. and. Moore. 1996),. a. rat. model. was. success-
fully.utilized.to.estimate.the.potential.uptake.(bioavailability)..This.can.then.
be.applied.to.provide.a.realistic.risk.assessment.in.calculating.the.potential.
exposure.route.via.soil.ingestion..For.example,.the.health.investigation.level.
(HIL).for.arsenic.in.soil.is.set.at.100.mg/kg.in.Australia.(NEPC.1999)..If.the.
arsenic.in.soil.is.only.10%.bioavailable.for.absorption,.then.the.real.value.for.
justifying.further.health.investigation.could.be.1000.mg.As/kg.soil.and.not.
100.mg. As/kg.. The. conventional. approach. assuming. that. metals. are. 100%.
bioavailable. for. absorption. is.very. conservative.and. often.gives.an.overes-
timation. of. the. real. risk.. Animal. models. have.widely. been.used. for.deter-
mining.the.bioavailability.of.metal.contamination.at.super-fund.sites.in.the.
United.States,.by.environmental.scientists.and.engineers..Although.animal.
models.are.regarded.as.the.ultimate.tool.for.the.assessment.of.contaminant.
uptake,.
in vitro
.physiologically.based.extraction.test.(PBET).for.bioaccessibil-
ity. measurement. has. been. gaining. momentum. and. acceptance. as. a. surro-
gate.test.for.predicting.bioavailability..The.application.of.several.such.
in vitro
.
bioaccessibility.assays.and.their.validation.against.an.
in vivo
.assay.has.been.
recently.reviewed.(Ng.et.al..2010).
In.this.study.we.utilized.bioaccessibility.data.as.a.pragmatic.approach.for.
a. more. structured. and. holistic. assessment. of. health. risk. posed. by. bauxite.
tailings.dust.
Methods
We. collected. 13. bauxite. tailings. samples. from. 3. adjoining. bauxite. tailings.
storage.dams.identiied.as.BT1,.BT2,.and.BT3.and.veranda.fall-out.dust.from.
2. houses. combined. into. 1. composite. dust. sample. in. the. residential. area.
downwind.from.the.bauxite.tailings.storage.facility.(see.sample.description.
in.Table.6.1)..The.dust.samples.collected.from.the.two.houses.were.combined.
in.equal.weight.to.yield.a.composite.house.dust.sample..The.residential.area.
studied. is. just. a. few. hundred. meters. downwind. from. the. closest. tailings.
dam.(Figure.6.1).
Particle-size.distribution.proiles.of.the.bulk.bauxite.tailings.were.obtained.
using. a. Malvern. Mastersizer. (Mastersizer. 2000,. Malvern. Instruments. Ltd.,.
Malvern,. United. Kingdom).. The. scanning. range. was. found. to. be. 0.02-
2000.μm,.based.on.a.default.RI.(refractive.index).of.1.52,.which.is.closer.to.the.
value.of.1.53.attributed.to.gibbsite.mineral.
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