EESA10 Lecture 5.pdf

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University of Toronto Scarborough
Environmental Science
Silvija Stefanovic

EESA10 Lecture 5 Monday, June 10, 2013 12:16 PM Cue Column: Note-Taking Area: Heavy Metals & Human Health Heavy Metals • Occurs naturally in earth ○ Widely dispersed in enviro  Traces is water, air etc. • Accumulatein tissues ○ Very toxic  Ex. Arsenic □ Metalloid Classification • Based on human impact/toxicology • Class A ○ Plants etc. need them; essential ○ Not toxic ○ Valent; +2 or +1 • Class B ○ Really toxic  Form soluble organometallics □ Organometallics - most toxic • Borderline ○ Micronutrients ○ Necessary but in very small amounts • Class B most toxic, Class A least, borderlinein between Mechanism of toxicity • Block essential functionalgroups ○ If blocked,enzymes, hormonescan't work • Displace other metals ○ Necessary ones can be displaced by toxic ones • Modifyingactive conformationof biomolecules ○ Change biomoleculeand not functioning Coping mechanisms • Resistance ○ Special species grow in soil butdon't take the metal; no change, as normally would be • Tolerance ○ Mechanism prevent attachment of metals to its sensitive receptors  Internal detoxifyingmechanisms □ Bind to other structure, butnot creating problem Bioavailability of metals • 'bio + available' if it's more available (the species of the metal) ○ Charged ions are more available than neutral (0)  pH can affect bioavailability
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