英语翻译alsocalledenvironmentalpollutiontheadditionofanysubstanceorformofenergy(e.g.,heat,sound,radioactivity)totheenvironmentataratefasterthantheenvironmentcanaccommodateitbydispersion,breakdown,recycling,orstoragei

　　英语翻译

　　alsocalledenvironmentalpollutiontheadditionofanysubstanceorformofenergy(e.g.,heat,sound,radioactivity)totheenvironmentataratefasterthantheenvironmentcanaccommodateitbydispersion,breakdown,recycling,orstorageinsomeharmlessform.

　　Apollutantneednotbeharmfulinitself.Carbondioxide,forexample,isanormalcomponentoftheatmosphereandaby-productofrespirationthatisfoundinallanimaltissues;yetinaconcentratedformitcankillanimals.Humansewagecanbeausefulfertilizer,butwhenconcentratedtoohighlyitbecomesaseriouspollutant,menacinghealthandcausingthedepletionofoxygeninbodiesofwater.Bycontrast,radioactivityinanyquantityisharmfultolife,despitethefactthatitoccursnormallyintheenvironmentasso-calledbackgroundradiation.

　　Pollutionhasaccompaniedmankindeversincegroupsofpeoplefirstcongregatedandremainedforalongtimeinanyoneplace.Primitivehumansettlementscanberecognizedbytheirpollutants—shellmoundsandrubbleheaps.Butpollutionwasnotaseriousproblemaslongastherewasenoughspaceavailableforeachindividualorgroup.Withtheestablishmentofpermanenthumansettlementsbygreatnumbersofpeople,however,pollutionbecameaproblemandhasremainedoneeversince.Citiesofancienttimeswereoftennoxiousplaces,fouledbyhumanwastesanddebris.IntheMiddleAges,unsanitaryurbanconditionsfavouredtheoutbreakofpopulation-decimatingepidemics.Duringthe19thcentury,waterandairpollutionandtheaccumulationofsolidwasteswerelargelytheproblemsofonlyafewlargecities.But,withtheriseofadvancedtechnologyandwiththerapidspreadofindustrializationandtheconcomitantincreaseinhumanpopulationstounprecedentedlevels,pollutionhasbecomeauniversalproblem.

　　Thevariouskindsofpollutionaremostconvenientlyconsideredunderthreeheadings:air,water,andland.