英语阅读理解100篇(中级篇)-英语题库

英语阅读理解100篇（中级篇）-11_英语题库

PassageEleven(TheAffectofElectricityonCancer)

Canelectricitycausecancer?Inasocietythatliterallyrunsonelectricpower,theveryideaseemspreposterous.Butformorethanadecade,agrowingbandofscientistsandjournalistshaspointedtostudiesthatseemtolinkexposuretoelectromagneticfieldswithincreasedriskofleukemiaandothermalignancies.Theimplicationsareunsettling,tosaytheleast,sinceeveryonecomesintocontactwithsuchfields,whicharegeneratedbyeverythingelectrical,frompowerlinesandantennastopersonalcomputersandmicro-waveovens.Becauseevidenceonthesubjectisinconclusiveandoftencontradictory,ithasbeenhardtodecidewhetherconcernaboutthehealtheffectsofelectricityislegitimate—ortheworstkindofparanoia.

NowthealarmistshavegainedsomequalifiedsupportfromtheU.S.EnvironmentalProtectionAgency.Intheexecutivesummaryofanewscientificreview,releasedindraftformlatelastweek,theEPAhasputforwardwhatamountstothemostseriousgovernmentwarningtodate.Theagencytentativelyconcludesthatscientificevidence“suggestsacasuallink”betweenextremelylow-frequencyelectromagneticfields—thosehavingverylongwave-lengths—andleukemia,lymphomaandbraincancer,WhilethereportfallsshortofclassifyingELFfieldsasprobablecarcinogens,itdoesidentifythecommon60-hertzmagneticfieldas“apossible,butnotproven,causeofcancerinhumans.”

Thereportisnoreasontopanic—oreventolostsleep.Ifthereisacancerrisk,itisasmallone.TheevidenceisstillsocontroversialthatthedraftstirredagreatdealofdebatewithintheBushAdministration,andtheEPAreleaseditoverstrongobjectionsfromthePentagonandtheWhitHouse.Butnownoonecandenythattheissuemustbetakenseriouslyandthatmuchmoreresearchisneeded.

Attheheartofthedebateisasimpleandwell-understoodphysicalphenomenon:Whenanelectriccurrentpassesthroughawire,titgeneratesanelectromagneticfieldthatexertsforcesonsurroundingobjects,Formanyyears,scientists

dismissedanysuggestionthatsuchforcesmightbeharmful,primarilybecausetheyaresoextraordinarilyweak.TheELFmagneticfieldgeneratedbyavideoterminalmeasuresonlyafewmilligauss,oraboutone-hundredththestrengthoftheearth’sownmagneticfield,Theelectricfieldssurroundingapowerlinecanbeashighas10kilovoltspermeter,butthecorrespondingfieldinducedinhumancellswillbeonlyabout1millivoltpermeter.Thisisfarlessthantheelectricfieldsthatthecellsthemselvesgenerate.

Howcouldsuchminusculeforcesposeahealthdanger?Theconsensususedtobethattheycouldnot,andfordecadesscientistsconcentratedonmorepowerfulkindsofradiation,likeX-rays,thatpacksufficientwalloptoknockelectronsoutofthemoleculesthatmakeupthehumanbody.Such“ionizing”radiationshavebeenclearlylinkedtoincreasedcancerrisksandthereareregulationstocontrolemissions.

Butepidemiologicalstudies,whichfindstatisticalassociationsbetweensetsofdata,donotprovecauseandeffect.ThoughthereisabodyoflaboratoryworkshowingthatexposuretoELFfieldscanhavebiologicaleffectsonanimaltissues,amechanismbywhichthoseeffectscouldleadtocancerousgrowthshasneverbeenfound.

ThePentagonisforfrompersuaded.Inablistering33-pagecritiqueoftheEPAreport,AirForcescientistschargeitsauthorswithhaving“biasedtheentiredocument”towardprovingalink.“Ourreviewersareconvincedthatthereisnosuggestionthat(electromagneticfields)presentintheenvironmentinduceorpromotecancer,”theAirForceconcludes.“ItisastonishingthattheEPAwouldlenditsimprimaturonthisreport.”ThenPentagon’sconcernisunderstandable.Thereishardlyaunitofthemodernmilitarythatdoesnotdependontheheavyuseofsomekindofelectronicequipment,fromhugeground-basedradartowerstothedefensesystemsbuiltintoeverywarshipandplane.

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Themainideaofthispassageis