HUMAN HEALTH AND ENVIRONMENT Lec 5: Heavy Metals and Human Health.doc

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University of Toronto Scarborough
Environmental Science
Jovan Stefanovic

HUMAN HEALTH AND ENVIRONMENTLec 5 Heavy Metals and Human Healthheavy metals are found in ores and extractednaturally occurringwide environmental dispersionsome heavy metals can bioaccumulatein liver brain bonescan be toxic in very low concentrations Classification of metalsthree classes A B and C borderline1Class Aexamples K Na Mg Camacronutrientsessential for biological processestend to form ionic bondlow toxicity but still toxicevery metal is toxic depending on the concentration2Class Bexamples Hg T Pb Ag Aunonessential elements for biological processestend to from covalent bondsvery toxicform solute organometallics3Class C Borderlineexamples Cr Cu As Co Ni Zn Mn Feessential for biological processes but only in small amountstrace minerals micronutrientstoxicity level is in between Class a and Class Bin order of increasing toxicity Class BClass CClass AMechanism of Toxicityblocks essential functional groups such as proteins enzymes which prevents the proteins from carrying anythingreceptors are blockedClass B and Class C metals can displace other metalsClass B can modify the active conformation of biomolecules from active to nonactiveCoping Mechanismsorganisms have mechanism to stop the effects of metalsresistancespecies develop mechanisms not to uptake metals they are resistantie plants dont take up lead tolerancethe capacity of species to withstand high level of metalsso organisms pick up the metal but it doesnt harm themthey can live normally with it in their systeminternal detoxifying mechanismsbinding to non sensitive compound structures
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