Environmental Engineering Reference
In-Depth Information
Three. intratracheal. instillation. studies. have. examined. the. pulmonary. toxicity. of.
SWCNTs.[23-25].
Lam.et.al..[23].instilled.mice.with.a.single.treatment.of.0,.0.1,.or.0.5.mg/mouse.
SWCNT.suspension.in.a.50.µL.buffer.(equal.to.approximately.3.94.×.10
6
.and.1.96.
×.10
7
.iber.units.per.mouse,.respectively)..Four.animals.per.dose.group.were.eutha-
nized.7.days.after.the.single.treatment;.ive.animals.per.dose.group.were.euthanized.
90.days.post.treatment..Lam.et.al..reported.dose-dependent.lesions,.primarily.inter-
stitial.granulomas,.in.both.the.7-.and.90-day.groups..The.lesions.were.more.promi-
nent. in. the. 90-day. animals.. Mice. also. were. treated. with. quartz. and. carbon. black.
(whose.size.range.included.nanoparticles)..Minimal.inlammation.was.observed.in.
mice.treated.with.carbon.black,.and.moderate.inlammation.was.observed.in.mice.
treated. with. quartz.. Lam. et. al.. reported. that. the. quartz-induced. toxicity. was. less.
severe.than.lesions.induced.by.SWCNTs.
In. a. second. study,. Warheit. et. al.. [25]. instilled. rats. with. SWCNTs. at. 0,. 1. or. 5.
mg/kg.(approximately.9.79.×.10
6
.and.4.90.×.10
7
.iber.units.per.rat,.respectively)..The.
research.team.euthanized.and.examined.animals.1,.7,.30,.or.90.days.after.a.single.
treatment..Granulomas.were.present.after.1.month.but.the.lesions.were.neither.dose.
dependent. nor. time. dependent.. Toxicity. was. not. reported. in. rats. that. were. treated.
with.graphite..Based.on.the.results,.Warheit.et.al..Concluded.that.“granulomatous.
reaction. was. a. nonspeciic. response. to. instilled. aggregates. of. SWCNTs. and. the.
results.may.not.have.physiological.relevance,.and.may.be.related.to.the.instillation.of.
a.bolus.of.agglomerated.nanotubes.”.Lam.et.al..[22].postulated.that.this.lack.of.dose.
and.time.dependence.reported.by.Warheit.et.al..[25].might.be.due.to.a.signiicant.
portion.of.the.instilled.bolus.dose.not.reaching.the.alveolar.region.
Shévedova.et.al..[24].conducted.a.third.study.in.an.attempt.to.resolve.the.differ-
ences.. In. this. study,. mice. were. instilled. with. a. SWCNT. suspension. that. had. been.
highly.puriied.to.remove.metals..Mice.were.administered.SWCNT,.carbon.black,.or.
quartz.at.0,.10,.20,.or.40.µg.per.mouse.(approximately.3.92.×.10
5
,.7.84.×.10
5
,.and.1.57.
×.10
6
.iber.units.per.mouse,.respectively)..Animals.were.euthanized.at.1,.3,.7,.28,.or.
60.days.following.a.single.treatment..Acute.pulmonary.inlammation,.granulomas,.
and.ibrosis.were.reported..The.pulmonary.toxicity.was.both.dose.and.time.depen-
dent..Similar.to.the.studies.conducted.by.Lam.et.al..[23].and.Warheit.et.al..[25],.gran-
ulomas.were.observed.at.the.site.of.deposition.of.SWCNT.aggregates,.but.unique.to.
this.study.was.the.dose-.and.time-dependent.interstitial.ibrosis.in.pulmonary.regions.
away.from.the.sites.of.deposition..These.data.indicate.ibrosis.induced.by.dispersed.
SWCNTs..Neither.carbon.black.nor.quartz.produced.granulomas.or.ibrosis.
Tian.et.al..[26].reported.that.SWNCTs.induced.the.strongest.adverse.effect.out.
of.ive.nano-sized.carbon.materials.tested.on.cultured.human.ibroblast.survival..The.
order.of.toxicity.from.least.to.most.toxic.was.as.follows:.carbon.graphite.<.multi-wall.
carbon.nanotubes.(MWCNTs).<.carbon.black.<.activated.carbon.<.SWCNT..Dis-
persed.SWCNTs.were.more.toxic.than.unreined.SWCNTs,.which.tended.to.group.
together.in.tangles,.creating.larger.and.less.harmful.ibrous.units.
The. results. of. these. animal. studies. indicate. that. SWCNTs. can. induce. inlam-
matory.pulmonary.toxicity.in.the.form.of.granulomas.that.can.result.in.ibrosis.if.
they.reach.the.deep.lung.tissue..Toxicity.in.the.upper.airway.is.mitigated.by.short.
residence.times.resulting.from.their.rapid.removal.
