EESA10 - Lec 5.rtf

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Environmental Science
Silvija Stefanovic

EESA10Lecture 5Heavy Metals And Human Health Heavy MetalsNaturally occurring extracted from the earth in ore Wide environmental dispersionTendency to accumulate in select tissuesToxic in even low concentrationsClassification of Metals1 Class AK Na Mg CaMacronutrients essential for biological processesTend to form ionic bondLow toxicity 2 Class BHg Pb TiNonessential elementsTend to form covalent bondVery toxic form soluble organometallics3 BorderlineCr Cu As Co Ni Zn Mn FeMicronutrientsToxicity ClassBorderlineClass AMechanism Of Toxicity1 Blocking essential functional groups such as proteins or enzymes proteins can not carry anything2 Displace other metals class B borderline3 Modifying the active conformation of biomolecules class BCoping MechanismsResistanceSpecies develop mechanisms not to uptake metal example PbTolerancethe capacity of species to withstand high level of metalsInternal detoxifying mechanismsBinding to nonsensitive compound structuresMetabolic transformations to less toxic forms methylation of As in marine biotaCan develop multiple toleranceCu Pb Zn CdBioavailability Of MetalsSpecies of the metalfree ions charged ions Znare more bioavailable than ZnNeutral species maybe bioavailable important in complexespH of solution Redox potential of solutionRoutes of ExposureInhalation dust or PM fume gasIngestion soil food plants accumulate metals in roots and leafsThrough the skinMostly accumulate in liver bones kidneyDamage the brain kidney some carcinogensHard to diagnose symptoms are weakness headachehypertensionMercury HgMetallic formin batteries dental amalgams thermometersThermometersWhen spilled mercury scatters into silver puddles and beads that give off an invisible vapour that is heavier than airBreathing this vapour is a health hazard e
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