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首页 不同频率的电磁场的生物效应有什么区别(What are the biological effec…

不同频率的电磁场的生物效应有什么区别(What are the biological effects of electromagnetic fields with different frequencies).doc

不同频率的电磁场的生物效应有什么区别(What are the…

Marvin陈平
2018-08-23 0人阅读 举报 0 0 暂无简介

简介:本文档为《不同频率的电磁场的生物效应有什么区别(What are the biological effects of electromagnetic fields with different frequencies)doc》,可适用于社会民生领域

不同频率的电磁场的生物效应有什么区别(Whatarethebiologicaleffectsofelectromagneticfieldswithdifferentfrequencies)不同频率的电磁场的生物效应有什么区别(Whatarethebiologicaleffectsofelectromagneticfieldswithdifferentfrequencies)WHOissuedadocumentonthe"internationalelectromagneticfieldsprojectinformation(FactSheets)formontheWHOwebsite,announcedbytherelationshipofdifferentfrequencyelectromagneticsourcesandpublichealthofficialopinionsissuedaftertheapprovaloftheAdvisoryCommitteeoftheplanWHOemphasizesthatthemechanismoftheactionofdifferentfrequencyelectromagneticsourcesonorganismsisdifferentTheeffectofEMFexposureonbiologicalsystemsdependsonthewavelength(frequency)andenergyoftheelectromagneticsourceofionizingradiation(IR)isahighfrequencyelectromagneticwave(Xraysandgammarays),ithasenoughphotonicenergytoelectronsofatomsormoleculesinthecollision,producepositivelychargedionsandnegativelychargedelectrons,whichproduceionizationFororganisms,itbreakstheDNAchemicalbondsincellgeneticmaterialmoleculesandformsdefinitehealthhazardsNonionizingradiation(NIR)isageneraltermforthelowerfrequencyandenergybandsintheelectromagneticspectrum(thewavelengthisgreaterthannm)Inthisband,thephotonenergyistooweaktoproduceionization,breakingthechemicalbondsbetweencellmoleculesTheyincludeultraviolet(UV)radiation,visiblelight,infrared,microwaveandradiofrequencyelectromagneticwaves,andextremelylowfrequencyelectricandmagneticfieldsNomatterhowhightheintensityofthenonionizingradiationis,itcannotcauseionizationinthebiologicalsystemNIR,however,producesotherbiologicaleffects,suchasfevereffectsandinvivoinducedcurrenteffectsWHOalsostressedthatsubstantialdifferencesneedtodistinguishthe"biologicaleffect"and"health":whenexposedtocauseanoticeorchangeofbiologicalsystemscanbedetectedintime,thatistheemergenceofbiologicaleffectsandwhenthebiologicaleffectsbeyondthenormalorganismcompensatoryrange,itmayproducethenegativehealtheffects,andcausesomehealthhazardWHOemphasizesthatbiologicaleffectsarenotallharmful,andsomeareevenbeneficialForexample,sunlightproducesheattoacceleratebloodflowintheskinexposuretosunlightcankeepoutthecold,orhelpthebodyactivatevitaminD,whichisanexampleofhealthbenefitsButsunburnorskincancermaybeharmfultoyourhealthTheradiofrequency(RF)fieldbelongstothenonionizingradiationrangeTheelectromagneticsourceRFfieldincludesadisplayandvideodisplayunit(~kHz),FMradio(kHz~MHz),industrialinductionheater(~MHz),microwaveheating,diathermy(~GHz),radar(~GHz),satellite,microwavecommunication(~GHz)andthesunlight(~GHz)ThebiologicaleffectsofexposuretoelectromagneticfieldsintheradiofrequencyrangearemainlythethermaleffectsandtheinducedcurrentsintheorganismtheRFfrequenciesinexcessofGHz,becauseofthehighfrequency,somostoftheenergyisabsorbedonthesurfaceoftheskin,onlyaverysmallenergypenetrationintothesubcutaneoustissue,thefrequencyofGHzormore,usethestrengthtomeasurethepowerdensity,thepowerpersquaremeter(Wm,mWmorWmmetering)WhenthepowerdensityoftheRFfieldismorethanWm,itcanproduceharmfulhealtheffectsthroughcellkilling(suchascataractandskinburns)SuchahighpowerdensitycannotbemetinthedailylifeenvironmentIt'sonlypossibletobenearastrongradar,buttheseareasareforbiddentostayRFfieldbelowGHz(toMHz)frequencycanpenetrateintothetissueandproducethermaleffectduetoabsorptionThedepthofpenetrationbecomesdeeperasthefrequencydecreasesTheabsorptionoftheRFfieldinvivocanbemeasuredbythespecificabsorptionrate(SAR)inacertaintissuemassTheunitofSARiswattsperkilogram(Wkg)Withinthisfrequencyrange,atleastWkgofSARexposureproducesknownharmfulhealtheffectsExposuretothisintensityonlyoccursattensofmetersawayfromtheFMFMantenna,whichprohibitspeoplefromenteringIntheMHzGHzband,theinductionofthermogenesisinthesomatictissuescantriggeravarietyofphysiologicalandthermalregulatoryresponses,includingtheabilitytoaccomplishtasks,Butthisharmfuleffectwillappearmorethandegreesriseintissueorbodytemperaturetheeffectoffetaldevelopment,malefertilityorbirthdefects,cataractsandotherhazardscanbeintemperaturetoDEGCwhen,butthisisnotexposureencounteredindailylifeThethermaleffectofRFfieldbelowMHzdoesnotreachthenoticeablelevel,butitinducescurrentandelectricfieldinbiologicaltissueThecurrentdensityofthebodyismeasuredbyanamperepersquaremeter(Am,mAm),andtheinducedcurrentisatleastovermAmtointerferewiththenormalfunctionoftheorganismorleadtoinvoluntarymusclecontractionTheAmericanAssociationofelectricalandElectronicEngineers(IEEE)thatusedinelectricfieldstrength(Vm)astheexposurelimitismoredirectandbasiclimit,correspondingprovisionsofthespecificpartsoftheelectricfieldstrengthallowsorganismsbasiclimitThecurrentmobilephonesystemusestoMHzworkingfrequencyTheexposureofmobilephoneusersishigherthanthatofpeoplelivingnearthecellularbasestation,butthemobilephoneonlysendsstrongradiofrequencyelectromagneticenergywhencalling,andthebasestationcontinuouslytransmitsthesignalWHOpointsoutthatnearthebasestationsaccessibletothepublic,radioexposurelevelsarefarbelowinternationalstandards,andusuallyhavenolessthantimesthesafetyfactorComparedwiththemobilecommunicationbasestationantenna,theradiofrequencyoftheTVandradiobroadcastantennaishigherAccordingtotheUSsurvey,theaverageRFbackgroundlevelinlargecitiesisaboutWm,andaboutoftheresidentsareexposedtotheRFfieldbeyondWmThedepthoftheRFfieldpenetratedintothetissuecanreachcmatthefrequencyofmobilecommunication,andtheheatgeneratedinthebodycanberemovedbythenormalthermalregulationofthehumanbodyWHOpointsoutthatnoresearchhasshownthatexposurelevelsbelowtheinternationalguidelineslimitharmfulhealtheffectsForallfrequenciesintheRFrange,WHOclearlypointsoutthattheexistingscientificevidencesuggeststhatexposuretotheradiofrequencyfieldisunlikelytocauseorpromotecancerSomeepidemiologicalstudiesareconcernedwiththeassociationbetweenRFexposureandcancerrisk,buttheseresultslackconsistencyandarenotsufficienttoassesstherelevanceofradiofrequencyexposuretocancerriskOtherbiologicaleffectsonthelivingenvironmentoflowintensityRFexposurealsointhestudy,somecellsobservedintheexperimenthasnotbeenconfirmed,onhumanhealthimplicationshavenotbeenrecognized,butnotasarestrictionofhumanexposurelimitfoundationAsfarastheextremelylowfrequencyelectricandmagneticfieldsareconcerned,internationalstudieshaveshownthatthemaininfluenceofthesefieldsonhumanbiologicalsystemsistheinductionofelectricfieldandcurrentinthebodyTheassociationbetweenlowlevelexposuretomagneticfieldsandchildhoodleukemiahasnotbeendemonstratedThestaticanddirectelectricfieldandmagneticfielddonotfindnoticeablehealtheffectsexceptfortheelectricaldischarge,themagneticforceinthebodyandtheinducedcurrentsofthemovingorganismsinveryhighfield

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不同频率的电磁场的生物效应有什么区别(What are the biological effects of electromagnetic fields with different frequencies)

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