Lecture_5_Heavy_metals - Heavy Metals and Human Health...

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Heavy Metals and Human Health
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Heavy Metals Naturally occurring, extracted from the earth in ore Wide environmental dispersion Tendency to accumulate in select tissues Toxic in even low concentrations
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Classification of metals 1. Class A: K, Na, Mg, Ca Macronutrients (essential for biological processes) Tend to form ionic bond Low toxicity 2. Class B: Hg, Ti, Pb, Ag, Au Nonessential elements Tend to form covalent bond Very toxic (form soluble organometallics)
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3. Borderline: Cr, Cu, As, Co, Ni, Zn, Mn, Fe Micronutrients Toxicity: Class B > Borderline > Class A Classification of metals
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Mechanism of toxicity 1. Blocking essential functional groups such as proteins or enzymes, proteins can not carry anything 2. Displace other metals (class B, borderline) 3. Modifying the active conformation of biomolecules (class B)
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Coping Mechanisms Resistance – species develop mechanisms not to uptake metal (example Pb) Tolerance – the capacity of species to withstand high level of metals Internal detoxifying mechanisms Binding to nonsensitive compound structures Metabolic transformations to less toxic forms (methilation of As in marine biota) Can develop multiple tolerance - Cu, Pb, Zn, Cd.
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Bioavailability of metals Species of the metal - free ions (charged ions Zn +2 are more bioavailable then Zn) Neutral species may be bioavailable, important in complexes pH of solution Redox potential of solution
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Inhalation (dust or PM, fume, gas) Ingestion (soil, food, plants accumulate metals in roots and leafs ) Through the skin Mostly accumulate in liver, bones, kidney
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This note was uploaded on 04/09/2011 for the course ENVIRONMEN EESA10 taught by Professor Silvajastovenovij during the Spring '11 term at University of Toronto.

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Lecture_5_Heavy_metals - Heavy Metals and Human Health...

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