Hexavalent Chromium Cr(vi) is a carcinogen Sources Steel-making cutting grinding and welding Spills and residues of electroplating baths Chromate emissions from cooling towers(used to inhibit corrosion)
Hexavalent Chromium • Cr (VI) is a carcinogen • Sources – Steel-making, cutting, grinding, and welding – Spills and residues of electroplating baths – Chromate emissions from cooling towers (used to inhibit corrosion)
Chemical basis for the toxicity of Hg, Cd, and Pb All three are soft"Lewis acids, i. e with large polarizability They have strong affinity for soft Lewis bases, such as the sulfhydryl side chain of cysteine residue The heavy metals likely exert their toxic effects by tying up critical cysteine residues in proteins 12 Lewis acid is a species that can form a H-C-CH2SH covalent bond by accepting an electron pair from another species COOH Lewis base is a species that can form a cysteine covalent bond by donating an electron pair to another species
Chemical basis for the toxicity of Hg, Cd, and Pb • All three are “soft” Lewis acids, i.e., with large polarizability. • They have strong affinity for soft Lewis bases, such as the sulfhydryl side chain of cysteine residue. • The heavy metals likely exert their toxic effects by tying up critical cysteine residues in proteins. cysteine NH2 C COOH H CH2 SH Lewis acid is a species that can form a covalent bond by accepting an electron pair from another species. Lewis base is a species that can form a covalent bond by donating an electron pair to another species