Environmental Engineering Reference
In-Depth Information
which.may.reasonably.be.anticipated.to.endanger.public.health.or.welfare.”
.Section.
108(a)(2). directs. the. EPA. to. publish. air. quality. “criteria”. for. each. listed. pollutant.
that.will.“accurately.relect.the.latest.scientiic.knowledge.useful.in.indicating.the.
kind.and.extent.of.all.identiiable.effects.on.public.health.or.welfare.which.may.be.
expected.from.the.presence.of.such.pollutant.in.the.ambient.air”.[29]..The.commonly.
used.term.“criteria.pollutant”.derives.from.this.provision.
Section.109.requires.the.EPA,.based.on.the.air.quality.criteria.in.Section.108,.
to.promulgate.numerical.“primary”.and.“secondary”.NAAQS.for.each.such.criteria.
pollutant.. Under. Section.109(b)(1),.a.primary. standard. is.one. that.will.protect.the.
public.health,.“allowing.an.adequate.margin.of.safety”.[30]..A.secondary.standard.is.
one.that.is.intended.to.protect.the.public.welfare.
.It.is.settled.law.that.considerations.
of.cost.or.technological.feasibility.are.not.to.play.a.role.when.the.EPA.establishes.
NAAQS.for.a.pollutant.[31-33].
NAAQS.have.been.established.for.six.criteria.pollutants.—.ozone,.particulate.
matter. (PM),. sulfur. dioxide,. nitrogen. oxide,. carbon. monoxide,. and. lead.. Among.
these,.it.is.the.PM.standards.that.offer.a.possible.pathway.for.regulating.nanoparticle.
emissions.under.the.CAA..Observing.that.particles.as.a.class.“span.many.sizes.and.
shapes. and. consist. of. hundreds. of. different. chemicals,”. the. EPA. describes. PM. as.
“a.highly.complex.mixture.of.solid.particles.and.liquid.droplets.distributed.among.
numerous.atmospheric.gases.that.interact.with.solid.and.liquid.phases”.[34]..Ambi-
ent.nanoparticles.are.the.smallest.among.them.
The.EPA's.original.NAAQS.for.PM.did.not.make.distinctions.by.particle.size,.
but.covered.all.PM.under.one.primary.standard.and.one.secondary.standard.estab-
lished.for.“total.suspended.particulate”.(TSP)..Subsequently,.as.scientists.and.regu-
lators.focused.their.attention.on.the.potential.health.effects,.and.also.the.impacts.on.
visibility,.associated.with.iner.—.as.opposed.to.coarser.—.particles.in.the.air,.the.
EPA.made.fundamental.changes.in.the.PM.standards..In.1987,.the.EPA.adopted.a.
inal.rule.that.replaced.the.TSP.measure.with.standards.written.in.terms.of.PM
10
,.
that.is,.particles.with.a.diameter.no.greater.than.10.micrometers.(µm).
Ten.years.later,.the.EPA.restructured.the.NAAQS.for.PM..The.EPA's.1997.revi-
sion.divided.the.PM.universe.by.size.for.standard-setting.purposes.into.two.groups:.
(1).“inhalable.coarse.particles”.(PM
10-2.5
),.those.between.2.5.and.10.µm.in.diameter;.
and.(2).ine.particles.(PM
2.5
),.those.with.a.diameter.of.2.5.µm.or.smaller..For.PM
2.5
,.
the.EPA.established.primary.NAAQS.of.15.µg/m
3
.(annual.standard).and.65.µg/m
3
.
.42.U.S.C..§.7408(a)(1)(A).and.(B)..The.term.“air.pollutant”.is.deined.broadly.in.Section.302(g),.42.
U.S.C..§.7602(g),.to.mean.“any.air.pollution.agent.or.combination.of.such.agents,.including.any.physi-
cal,. chemical,. biological,. radioactive. (including. source. material,. special. nuclear. materials,. and. by-
product.material).substance.or.matter.which.is.emitted.into.or.otherwise.enters.the.ambient.air..Such.
term.includes.any.precursors.to.the.formation.of.any.air.pollutant,.to.the.extent.the.Administrator.has.
identiied.such.precursor.or.precursors.for.the.particular.purpose.for.which.the.term.'air.pollutant'.is.
used.”
.CAA.§.109(b)(2),.42.U.S.C..§.7409(b)(2)..No.“margin.of.safety”.is.called.for.in.establishing.a.second-
ary.NAAQS.
