Chapter9-ReproductiveSystemREPRODUCTIVESYSTEM:INTRODUCTIONLowellE.SeverMaleandfemalereproductivetoxicityaretopicsofincreasinginterestinconsiderationofoccupationalhealthhazards.Reproductivetoxicityhasbeendefinedastheoccurrenceofadverseeffectsonthereproductivesystemthatmayresultfromexposuretoenvironmentalagents.Thetoxicitymaybeexpressedasalterationstothereproductiveorgansand/ortherelatedendocrinesystem.Themanifestationsofsuchtoxicitymayinclude:·alterationsinsexualbehaviour·reducedfertility·adversepregnancyoutcomes·modificationsofotherfunctionsthataredependentontheintegrityofthereproductivesystem.Mechanismsunderlyingreproductivetoxicityarecomplex.Morexenobioticsubstanceshavebeentestedanddemonstratedtobetoxictothemalereproductiveprocessthantothefemale.However,itisnotknownwhetherthisisduetounderlyingdifferencesintoxicityortothegreatereaseofstudyingspermthanoocytes.DevelopmentalToxicityDevelopmentaltoxicityhasbeendefinedastheoccurrenceofadverseeffectsonthedevelopingorganismthatmayresultfromexposurepriortoconception(eitherparent),duringprenataldevelopmentorpostnatallytothetimeofsexualmaturation.Adversedevelopmentaleffectsmaybedetectedatanypointinthelifespanoftheorganism.Themajormanifestationsofdevelopmentaltoxicityinclude:·deathofthedevelopingorganism·structuralabnormality·alteredgrowth·functionaldeficiency.Inthefollowingdiscussion,developmentaltoxicitywillbeusedasanall-inclusivetermtorefertoexposurestothemother,fatherorconceptusthatleadtoabnormaldevelopment.Thetermteratogenesiswillbeusedtorefermorespecificallytoexposurestotheconceptuswhichproduceastructuralmalformation.Ourdiscussionwillnotincludetheeffectsofpostnatalexposuresondevelopment.MutagenesisInadditiontoreproductivetoxicity,exposuretoeitherparentpriortoconceptionhasthepotentialofresultingindevelopmentaldefectsthroughmutagenesis,changesinthegeneticmaterialthatispassedfromparenttooffspring.Suchchangescanoccureitheratthelevelofindividualgenesoratthechromosomallevel.Changesinindividualgenescanresultinthetransmissionofalteredgeneticmessageswhilechangesatthechromosomallevelcanresultinthetransmissionofabnormalitiesinchromosomalnumberorstructure.Itisinterestingthatsomeofthestrongestevidenceforaroleforpreconceptionexposuresindevelopmentalabnormalitiescomesfromstudiesofpaternalexposures.Forexample,Prader-Willisyndrome,abirthdefectcharacterizedbyhypotonicityinthenewbornperiodand,later,markedobesityandbehaviourproblems,hasbeenassociatedwithpaternaloccupationalexposurestohydrocarbons.Otherstudieshaveshownassociationsbetweenpaternalpreconceptionexposurestophysicalagentsandcongenitalmalformationsandchildhoodcancers.Forexample,paternaloccupationalexposuretoionizingradiationhasbeenassociatedwithanincreasedriskofneuraltubedefectsandincreasedriskofchildhoodleukaemia,andseveralstudieshavesuggestedassociationsbetweenpaternalpreconceptionoccupationalexposuretoelectromagneticfieldsandchildhoodbraintumours(GoldandSever1994).Inassessingbothreproductiveanddevelopmentalhazardsofworkplaceexposuresincreasedattentionmustbepaidtothepossibleeffectsamongmales.Itisquitelikelythatsomedefectsofunknownaetiologyinvolveageneticcomponentwhichmayberelatedtoparentalexposures.Becauseofassociationsdemonstratedbetweenfather'sageandmutationratesitislogicaltobelievethatotherpaternalfactorsandexposuresmaybeassociatedwithgenemutations.Thewell-establishedasso...
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