Environmental Engineering Reference
In-Depth Information
most. vulnerable. target. organ.. In. terrestrial. animals,. nanomaterials. may. pose. the.
greatest.risk.to.the.lung,.as.they.can.be.transported.like.a.gas.to.reach.the.alveoli.in.
the.deepest.portion.of.the.lungs..In.aquatic.organisms,.nanoparticles.may.be.absorbed.
as.water.is.passed.over.gill.membranes.at.a.fairly.rapid.rate.to.extract.the.dissolved.
oxygen.that.is.absolutely.necessary.to.sustain.the.life.of.an.individual.organism.
8.2.3
s
ummary
A.host.of.factors.will.determine.both.the.degree.of.exposure.and.the.toxicity.of.nano-
materials.to.either.terrestrial.or.aquatic.receptors:.the.type.of.environmental.recep-
tor,. its. habitat,. the. duration. of. exposure,. age,. gender/sex,. sensitivity. or. tolerance,.
adaptive.mechanisms,.and.the.composition,.size,.shape,.surface.area,.solubility,.and.
concentration.of.the.nanomaterial.in.question..The.challenge.in.solving.the.puzzle.
is.considerable..Technology.will.have.to.rise.to.meet.the.problem.of.dosimetry.(i.e.,.
generating.and/or.measuring.airborne.nanomaterials)..No.standard.metrics.currently.
exist. for. quantifying. the. inhaled. dose. (particles/m
3
?,. surface. area/m
3
?,. mg/m
3
?)..
Current.research.programs.are.not.universally.aligned.with.regard.to.testing.proto-
cols..Finally,.because.of.the.explosion.of.new.materials,.combined.with.the.current.
lack. of. information. on. how. different. nanomaterials. behave. and/or. enter. the. body,.
there.will.be.considerable.uncertainty.in.the.use.of.current.predictive.models.such.as.
physiologically.based.pharmacokinetic.models.
The.remainder.of.this.chapter.discusses.the.effects.of.nanomaterials.on.terres-
trial.and.aquatic.receptors..For.terrestrial.receptors,.inhalation.will.be.the.key.expo-
sure.pathway.and.the.lung.will.be.the.key.target.organ,.should.nanomaterials.enter.
the. general. environment. via. air.. The. brain. also. may. be. a. target. if. uptake. occurs.
through.the.olfactory.nerves..Similarly,.for.aquatic.receptors,.water.will.be.the.obvi-
ous.route.of.exposure.and.the.respiratory.system,.namely.the.gills.(whether.they.be.
internal.gills.of.a.ish.or.the.external.gills.of.some.types.of.benthic.invertebrates),.are.
expected.to.be.the.key.target.organ.
.
antiCiPated hazaRds to teRRestRial eCosYsteMs
At. the. lower. levels. of. the. food. web,. some. nanomaterials. appear. to. possess. potent.
antibacterial.properties.[15-17],.particularly.materials.containing.silver..Researchers.
have.exposed.microorganisms.(
Escherichia coli
).to.nanomaterials.containing.silica,.
silica/iron.oxide,.and.gold.to.examine.the.antibacterial.response,.but.the.growth.stud-
ies.have.“indicated.no.overt.signs.of.toxicity”.[18]..Similarly,.exposure.of.a.soil.micro-
bial.community.to.C60.fullerenes.had.little.impact.on.the.structure.and.function.of.
the.community.and.associated.microbial.processes.[19]..Fullerenes.in.water.suspen-
sions,.however,.“exhibited.relatively.strong.antibacterial.activity”.[20],.with.fractions.
containing.smaller.aggregates.showing.higher.toxicity.even.though.the.“increase.in.
toxicity.was.disproportionately.higher.than.the.associated.increase.in.putative.sur-
face. area.”. Aqueous. suspensions. of. SiO
2
,. TiO
2
,. and. ZnO,. however,. showed. strong.
antibacterial. activity. (
Bacillus subtilis
),. apparently. through. the. generation. of. ROS.
[7]..The.study.conclusions.“highlight.the.need.for.caution.during.use.and.disposal.of.
such.manufactured.nanomaterials.to.prevent.unintended.environmental.impacts.”
