Environmental Engineering Reference
In-Depth Information
Few.studies.to.date.have.examined.the.results.of.dermal.exposure,.but.one.study.
exposing.both.human.and.rabbit.skin.to.fullerene.soot.containing.carbon.nanotubes.
using.patch.tests.[21].could.not.ind.that.the.mixture.posed.any.risks..Another.study.
used.six.different.types.of.quantum.dots.under.12.nm.in.size.[22].and.coated.with.
neutral,.anionic,.or.cationic.shells..The.results.showed.penetration.of.intact.porcine.
skin.using.
in vitro
.low-through.diffusion.cells.at.occupationally.relevant.doses..Full.
penetration.could.not.be.conirmed.as.the.perfusate.was.negative.for.the.detection.
of.quantum.dots,.with.a.detection.limit.of.0.5.to.1.0.nm..The.authors.state.that.the.
skin.was.permeable.to.these.structures.in.that.they.“penetrated.the.stratum.corneum.
and.localized.within.the.epidermal.and.dermal.layers.by.8.hours,”.but.others.(car-
boxylic.acid.coated).were.less.effective..In.any.event,.although.intact.skin.may.be.a.
potential.pathway.for.the.absorption.of.nanomaterials,.the.potential.for.signiicant.
exposure.via.skin,.at.least.for.terrestrial.organisms,.appears.to.be.the.least.probable.
with.regard.to.the.three.available.exposure.pathways.
Inhalation.may.be.the.most.signiicant.exposure.pathway.for.terrestrial.organ-
isms. should. an. ongoing. release. of. nanomaterials. occur.. The. concept. of. ongoing.
release. is. important. because. these. ultraine. materials,. like. their. larger. iber. coun-
terparts,.will.only.induce.a.signiicant.pathology.such.as.inlammation,.production.
of.biologically.active.substances.by.the.RES,.ibrosis,.or.calciication.upon.
chronic
exposure
..Ironically,.we.may.have.already.performed.this.type.of.an.experiment.in.
the.real.world,.as.urban.air.pollution.undoubtedly.contains.particulate.matter.in.the.
sub-micrometer.range.[23]..Particulate.matter.(in.the.form.of.“PM
10
,”.or.particulate.
matter.that.will.pass.through.a.10-µm.ilter),.principally.in.the.form.of.exhaust.fumes.
and.dusts.generated.by.the.natural.activity.of.urban.life,.was.(and.still.is).a.major.
cause.of.pulmonary.disease.in.urban.and.suburban.environs.
Most. research. is. still. in. the. early. phases.. With. a. few. exceptions,. most. of. the.
indings.with.regard.to.respiratory.pathology.following.exposure.of.laboratory.ani-
mals. are. not. that. different. from. studies. performed. using. more. traditional. toxico-
logical.testing.of.inhaled.particulate.materials..Symptoms.include.ibrotic.reactions.
such. as. granulomas,. which. are. nonspeciic. lesions. in. response. to. solid. matter. in.
tissue;.an.increase.in.number.and/or.activity.of.macrophages;.oxidative.stress-related.
inlammation. (usually. due. to. the. formation. of. short-lived. but. reactive. molecules);.
tumor-related.effects.in.rats.(although.this.response.may.have.been.due.to.“overload.
conditions”);.and.a.quite.unique.response.to.nanoparticles,.which.is.their.uptake.by.
the.olfactory.epithelium.into.the.brain.[24]..Nanoparticulate.translocation.to.other.
areas.of.the.body.appears.to.be.speciic.to.the.unique.properties.of.each.individual.
nanomaterial.(i.e.,.composition,.size,.shape,.surface.area,.water.solubility,.and.ten-
dency.to.form.aggregates).
.
antiCiPated hazaRds to aQuatiC eCosYsteMs
Scientists.most.likely.will.use.bioassay.techniques,.based.on.years.of.experience.with.
dissolved.chemicals,.to.evaluate.the.aquatic.hazards.of.nanomaterials..This.section.
opens.with.a.brief.discussion.of.those.techniques.and.their.limitations.with.respect.
to.nanomaterials..It.then.discusses.the.toxicity.of.six.target.nanomaterials:.carbon.
black,. fullerenes,. carbon. nanotubes,. silver,. zero-valent. iron,. and. titanium. dioxide..
Throughout,.this.discussion.refers.to.the.summary.of.literature.in.Table.8.1.
