Environmental Engineering Reference
In-Depth Information
To. convert. this. to. a. human. exposure,. the. concentration. in. the. mouse. must. be.
scaled.to.a.human..Given.that.the.mouse.mass.in.the.study.by.Shevedova.et.al..[24].
was.reported.to.be.20.3.g,.it.is.possible.to.estimate.the.total.lung.volume.(
V
tot
).as.the.
sum.of.the.tidal.volume.(i.e.,.the.amount.of.air.passing.in.and.out.of.the.lung.during.
normal.resting.breath;.
V
T
).and.the.anatomical.dead.space
.(
V
D
).for.the.mouse.and.a.
75-kg.human.using.the.algometric.scaling.equations.of.Linstedt.and.Schaffer.[30].
as.follows:
Mouse W
(
=
0 0203
.
kg
) :
1 01
.
V
=
6 60
.
⋅
W
=
0 129
.
mL
T
kg
1 01
.
V
=
2 20
.
⋅
W
=
0 0430
.
mL
D
kg
V
=
0 172
.
mL
tot
.
.
9.13)
Human W
(
=
75 0
.
kg
) :
1 01
.
V
=
6 60
.
⋅
W
=
517
mL
T
kg
1
.
01
V
=
2 20
.
⋅
W
=
172
mL
D
kg
V
=
689
mL
tot
Absolute. pulmonary. surface. area. (
SA
). is. dificult. to. determine. because. of. the.
irregular.geometry..However,.by.assuming.proportional.scaling.to.the.total.pulmo-
nary.volume.between.the.mouse.and.human,.the.relative.surface.area.for.the.human.
and.the.mouse.can.be.scaled.as.follows:
2 3
/
V
V
SA
SA
.
tot
−
human
human
= 252
.
(9.14)
=
tot
−
mouse
mous
e
With.an.area.scaling.factor.of.252.human.to.mouse,.a.safe.dose.of.3.92.×.10
5
.iber.
units.per.mouse.can.be.extrapolated.to.9.88.×.10
7
.ibers.per.person..This.level.can.be.
considered.a.not-to-exceed.body.burden.for.ibers.less.than.5.µm.in.effective.diam-
eter,.which.is.the.typical.upper.size.limit.for.materials.that.are.capable.of.reaching.
the.deep.lung.
Muller.et.al..[31].reported.the.clearance.from.the.deep.lung.for.MWCNTs.as.a.
constant.for.elimination.(
k
β
).of.0.01.days.or.a.half-life.of.69.3.days..This.assumed.
an.inherent.interaction.between.the.MWCNT.and.the.pulmonary.physiology,.and.is.
.Anatomical.dead.space.(VD):.the.volume.of.the.conducting.airways.from.the.external.environment.(at.
the.nose.and.mouth).down.to.the.level.at.which.inspired.gas.exchanges.oxygen.and.carbon.dioxide.with.
pulmonary.capillary.blood;.formerly.presumed.to.extend.down.to.the.beginning.of.alveolar.epithelium.
in.the.respiratory.bronchioles,.but.more.recent.evidence.indicates.that.effective.gas.exchange.extends.
some.distance.up.the.thicker-walled.conducting.airways.because.of.rapid.longitudinal.mixing.
