Environmental Engineering Reference
In-Depth Information
communication.both.at.work.and.socially..It.may.cause.the.worker.to.lose.his.or.her.
job.if.acute.hearing.is.required.to.perform.effectively..The.loss.of.hearing.is.dei-
nitely.a.handicap.to.the.worker.
nonIonIzIng rAdIAtIon
Nonionizing. radiation. is. a. form. of. electromagnetic. radiation,. and. it. has. varying.
effects.on.the.body,.depending.largely.on.the.particular.wavelength.of.the.radiation.
involved.. In. the. following. paragraphs,. in. approximate. order. of. decreasing. wave-
length.and.increasing.frequency,.are.some.hazards.associated.with.different.regions.
of. the. nonionizing. electromagnetic. radiation. spectrum.. Nonionizing. radiation. is.
covered.in.some.detail.by.29.CFR.1910.97.
Nonionizing.radiation.is.usually.low.frequency,.with.longer.wavelengths,.includ-
ing.powerline.transmission.frequencies,.broadcast.radio,.and.shortwave.radio..Each.
of. these. can. produce. general. heating. of. the. body.. The. health. hazard. from. these.
radiations.is.very.small,.however,.as.it.is.unlikely.that.they.would.be.found.in.intensi-
ties.great.enough.to.cause.signiicant.effect..An.exception.can.be.found.very.close.to.
powerful.radio.transmitter.aerials.
Microwaves.have.wavelengths.of.3.m.to.3.mm.[100.to.100,000.megahertz.(MHz)]..
They. are. found. in. radar,. communications,. some. types. of. cooking,. and. diathermy.
applications..Microwave.intensities.may.be.suficient.to.cause.signiicant.heating.of.
tissues..The.effect.is.related.to.wavelength,.power.intensity,.and.time.of.exposure..
Generally,.longer.wavelengths.produce.greater.penetration.and.temperature.rise.in.
deeper.tissues.than.shorter.wavelengths..However,.for.a.given.power.intensity,.there.
is.less.subjective.awareness.to.the.heat.from.longer.wavelengths.than.there.is.to.the.
heat. from. shorter. wavelengths. because. absorption. of. longer. wavelength. radiation.
takes.place.beneath.the.body's.surface.
An. intolerable. rise. in. body. temperature,. as. well. as. localized. damage. to. spe-
ciic. organs,. can. result. from. an. exposure. of. suficient. intensity. and. time.. In. addi-
tion,.lammable.gases.and.vapors.may.ignite.when.they.are.inside.metallic.objects.
located.in.a.microwave.beam..Power.intensities.for.microwaves.are.given.in.units.of.
.milliwatts. per. square. centimeter. (mW/cm
2
),. and. areas. having. a. power. intensity. of.
over.10 mW/cm
2
.for.a.period.of.0.1.hours.or.longer.should.be.avoided.
Radio.frequency.(RF).and.microwave.(MW).radiation.are.electromagnetic.radia-
tion.in.the.frequency.range.3.kilohertz.(kHz).to.300.gigahertz.(GHz)..Usually,.MW.
radiation.is.considered.a.subset.of.RF.radiation,.although.an.alternative.convention.
treats.RF.and.MW.radiation.as.two.separate.spectral.regions..Microwaves.occupy.
the.spectral.region.between.300.GHz.and.300.MHz,.while.RF.or.radio.waves.include.
300.MHz.to.3.kHz..RF/MW.radiations.are.nonionizing.in.that.there.is.insuficient.
energy.[less.than.10.electron.volts.(eV)].to.ionize.biologically.important.atoms..The.
primary.health.effects.of.RF/MW.energy.are.considered.thermal..The.absorption.of.
RF/MW.energy.varies.with.frequency..Microwave.frequencies.produce.a.skin.effect.
(a.person.can.literally.sense.their.skin.starting.to.feel.warm)..RF.radiation.may.pen-
etrate.the.body.and.be.absorbed.in.deep.body.organs.without.the.skin.being.affected,.
which.can.warn.an.individual.of.danger..A.great.deal.of.research.has.turned.up.other.
nonthermal.effects..All.the.standards.of.Western.countries.have,.so.far,.based.their.
