Environmental Engineering Reference
In-Depth Information
testosterone.levels.and.presented.with.micropenis.and.disorganized.testes.
(Guillette. et. al..1994,. 1995,.Guillette.and. Guillette. 1996).. Other. reports.also.
highlighted. the. pathophysiological. consequences. of. chemical. exposures.
that. affect. reproductive. functions. in. mammals,. bird,. amphibian,. and. ish.
(Aravindakshan.et.al..2004,.Barnhoorn.et.al..2004,.De.Guise.et.al..1994,.Fry.
1995,.Hayes.et.al..2003,.Jobling.et.al..2002,.Mansield.and.Land.2002,.Oskam.
et.al..2003).
In.human.epidemiologic.study,.a.signiicant.reduction.in.the.ratio.of.“male.
birth. to. total. number. of. birth”. was. recorded. in. the. Aamjiwnaang. First.
Nation. community. (areas. close. to. industrial. areas). in. Canada. (Mackenzie.
et.al..2005).. During.the.episode.of.PCBs.and.dioxin.food.contamination.in.
Belgium.in.the.year.1999,.a.study.of.reproductive.status.in.local.male.popu-
lation. indicated. that. the. rise. of. serum. dioxin. levels. were. associated. with.
a. decrease. of. serum. testosterone. levels. and. a. reduction. of. semen. volume.
(Dhooge.et.al..2006)..Occupational.study.also.revealed.that.the.exposure.to.
phthalate. (substances. added. to. plastics. to. increase. their. lexibility). caused.
signiicant.reduction.of.serum.testosterone.level.(Pan.et.al..2006)..In.addition,.
epidemiological.studies.reported.an.increased.risk.of.genital.malformations.
and.cryptorchidism.in.children.of.workers.who.were.exposed.to.pesticides.
(Garcia-Rodriguez.et. al..1996,.Weidner.et. al.. 1998).. Collectively,. the. reports.
have. conirmed. the. association. between. reproductive. disorders. and. the.
accumulation.of.environmental.pollutants.
EndocrineDisruptorsandTheirGeneralMechanisticActions
Most.of.the.pollutants.are.known.as.endocrine.disruptors.(EDs).(Crews.and.
McLachlan.2006)..EDs.can.affect.the.hormonal.system.via.(but. not.limited.
to). estrogenic,. androgenic,. antiandrogenic,. and. antithyroid. mechanisms.
and/or. modulation. of. steroidogenesis/steroid. metabolism. (Phillips. et. al..
2008,.Phillips.and.Foster.2008b)..With.the.beneit.of.hindsight,.the.endocrine-.
disrupting. effects. of. environmental. contaminants. have. been. shown. to.
impose.acute.and/or.long-term.effect.on.animal.development..As.the.most.
toxic. man-made. pollutant,. dioxins. are. known. to. impose. biological. effects.
via. the. aryl. hydrocarbon. receptor. (AhR),. which. belongs. to. a. member. of.
the. basic. helix-loop-helix/Per-Arnt-Sim. (bHLH/PAS). family. of. transcrip-
tion. factors.. AhR. exhibits. its. transcriptional. activity. primarily. via. ligand-
dependent. nuclear. translocation. (Mimura. and. Fujii-Kuriyama. 2003).. The.
role. of. AhR. in. mediating. dioxins-elicited. developmental. toxicity. has. been.
demonstrated.using.zebraish.model.(Carney.et.al..2006,.Prasch.et.al..2003)..
Other.AhR-mediated.regulatory.functions.include.the.modulation.of.other.
transcriptional.factors,.including.Rb/E2F,.NFκB,.and.the.estrogen.(ERα.and.
ERβ). and. androgen. receptors. (Beischlag. and. Perdew. 2005,.Matthews. et.al..
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