研究生英语精读教程第三版上unit-two

UnittwoText:Cancer&Chemicals-AreWeGoingTooFar?MarlaConeLastyear,CaliforniagovernorGeorgeDeukmejiancalledtogethermanyofthestate'sbestscientificmindstobeginimplementingProposition65,thestate'sSafeDrinkingWaterandToxicEnforcementAct.Thisnewlawbansindustriesfromdischargingchemicalsuspectedofcausingcancer(carcinogens)orbirthdefectsintowatersupplies.Someclaimitwillalsorequirewarninglabelsoneverythingthatmightcausecancer.Adayofesotericscienceandincomprehensiblejargonwaspredicted.ButBruceAmes,chairmanofthedepartmentofbiochemistryattheUniversityofCaliforniaatBerkeley,hadplanstoliventheproceedings.Walkingintotheroom,Ameslookedlikethequintessentialscientist:wire-rimmedbifocals,rumpledsuit,tousledhairandasallowcomplexionthatshowedhespentmoretimeinhislaboratorythanintheCaliforniasunshine.Assomeoneintonedaboutthemechanismsofcarcinogenesis,Amesbegantointerjecthisownviews.Thewholeworldischock-fullofcarcinogens,Amesdeclared.“Abeer,withits700partsperbillionofformaldehydeandfivepartsper100ofalcoholisathousandtimesmorehazardousthananythinginthewater.Ifyouhavebeeronyourbreath,doesthatmeanyouhavetowarneveryonewhocomeswithintenfeetofyou?Inanerawhenheadlinesshoutaboutthelatestcancerscare,Ameshasadifferentmessage:thelevelsofmostman-madecarcinogensaregenerallysolowthatanydangeristrivialcomparedwiththelevelsofnaturalcarcinogens.Amesisnotaquack.Atage59,heisoneofthenation'smostrespectedauthoritiesoncarcinogenesis.Hisresumeispackedwithhonors,includingtheCharles.MottPrizefromtheGeneralMotorsCancerResearchFoundation,oneofthemostprestigiousawardsincancerresearch,andmembershipintheNationalAcademyofSciences.EvenhiscriticssaytheAmestest—hissimple,inexpensivelaboratoryprocedurethathelpsdeterminewhetherasubstancemightcausecancer—isaremarkableachievement.ButAmesslaughterssacredcows.He'stakingontheenvironmentalmovement,whichsomehavecalledthesinglemostimportantsocialmovementofthe20thcentury.InApril1987,forinstance,heandtwocolleagues,RenaeMagawandLoisSwirskyGold,publishedareportinSciencemagazinethatrankedvariouspossiblecancerrisks.Basedonanimaltestsofnearly1,000chemicals,thedatashowthatdailyconsumptionoftheaveragepeanut-buttersandwich,whichcontainstracesofaflatoxin(anaturallyoccurringmoldcarcinogeninpeanuts),is100timesmoredangerousthanourdailyintakeofDDTfromfood,andthataglassofthemostpollutedwellwaterintheSiliconValleyis1,000timeslessofcancerriskthanaglassofwineorbeeris.He'snotadvisingpeopletostopconsumingpeanut-butter,beerandwine.Whathe'ssayingisthatmostcancerriskscreatedbymanaretrivialcomparedwitheverydaynaturalrisks,andit'snotclearhowmanyofthesearerealrisks.Bothtypesdistractattentionfromsuchenormousriskfactorsastobacco.Ames'scancerresearchbeganabout25yearsagooverabagofpotatochips.Ames,thenconductingresearchfortheNationalInstitutesofHealthinMaryland,wasreadingtheingredientsonthebag.Itstruckhimthatnooneknewwhateachchemicaldidtohumangenes,andtherewasnoeasywaytofindout.Atthattime,scientiststestingforcarcinogenicityhadtosetuptimeconsumingandcostlylabexperimentsonratsandmice.Armedwiththeknowledgethatbacteriaaresensitivetosubstancesthatcausemutation,andthatcarcinogenswerelikelytobemutagens,Amesdevelopedacarcinogentestusingbacteria.TheAmestestwashailedasamajorscientificdevelopmentandisnowusedworldwide.Onedayin1974Ames,nowteachingatBerkeley,suggestedthatsomestudentstestvarioushouseholdproducts.Tohissurprise,manycommonhairdyestestedpositive,asdidaflameretardantusedinchildren'spajamas.Almostovernight,Amesbecameaheroofenvironmentalistswhenhisfindingsledtonewregulationsandbansoncertainchemicals.Forthenextdecadepublicconcernovercarcinogenscontinuedtorise.Then,Amessays,Istartedrealizingsomethingwasn'tright.Toomanynaturalsubstancesalsotestedpositiveascarcinogensormutagens:fruitjuices,brownmustard,celery,parsley.Infact,abouthalfofallchemicalstestedbyAmes—bothnaturalandman-made—turnedouttobepotentiallycarcinogenicwhengiveninenormousdosestoratsandmice.Amesatfirstassumedhehaderredwithhistest.Hehadn't.Hiserrorhadbeenmakingthecommon,butnaive,assumptionthatonlyman-madechemicalscouldbedangerous.Whyassumenatureisbenign?henowsays.ThecampaignsupportingCalifornia'sProposition65convincedAmesthathehadadutytoexplainthistothepublic.Whenpeoplesaidcertainbirthdefectswerecausedbyapartperbillionofsomethinginthewater,Ithoughtitirresponsible,hesays.It'sjustplayingwithpeople'sfears.Youcanalwaysfindapartperbillionofsomethinginthewater.IntestimonybeforeaCaliforniasenatecommittee,Amesnotedthattapwater,forinstance,containsthecarcinogenchloroformatabout83ppbduetochlorination.Butcoffeecontainstwonaturalcarcinogensatabout4,000ppbeach,whilehumanbloodaverages3,000ppbofformaldehydefromnormalmetabolism.SomepeopleassumeAmesisastoogeforthechemicalindustry,whichheisnot.Hedoesnoconsultingforthechemical,drugorfoodcompanies,orforlawfirms.Andheacceptsnograntsfrombusiness.EnvironmentalistsrejectAmes'sarguments,sayingthatweareobligatedtokeepthetotalexposuretocarcinogensaslowaspossible.Somehowhethinkstherehastobeachoice,saysCarlPopeoftheSierraClub.IfwehadtochoosebetweenTCE[asuspectedcancercausingsolvent]