Metals and Metal Toxicity

1

• Metals and Metal Toxicity
• Metals
• Biologically Impt Metals
• Metal Pollution Toxicity
• Examples Arsenic, Cadmium, Mercury, Lead

2
Global Metal Use and Emissions
3
Periodic Table
Heavy Metals
4
Iron
Myoglobin
Hemoglobin
Carboxypeptidase
Zinc
Vitamin B-12
Cobalt
5
Beneficial vs Toxic Effects
6
Sources Routes of Exposure
7
Relative Toxicity to Individuals
8
Toxicity Classes
Bullies
Tweeners
Wimps
9

• Metals in the Environment
• natural weathering vs
• env. transport altered speciation
• old vs new metals
• Metal Homeostasis
• metallothioneins
• early development
• plant tolerance
• Bioconcentration vs Bioaccumulation
• storage in individuals vs.
• magnify up the food chain (eg. Hg)

10

• General Principles of Metal Toxicity
• affect multiple organs
• metal ion binds enzymes membrane proteins
• (ER, lysosomes, mitochondria, etc)
• CH3-metal can cross membrane
• chelators metalothioneins neutralize ion
• children elderly most vulnerable

• Chelators
• BAL contains 2 SH to attract As
• Calcium EDTA choice for Pb poisoning

11

• Arsenic
• By-product of Cu, Pb, Zn smelting
• Glass mfg
• Pesticides
• Accum. In skin (eg. Sweat, fingernails, hair,
  breast milk)
• Toxic Effects S-seeking
• Cell binds S, blocks mitochon. respir. Enzymes
• Chronic- distal neuropathy, demyelination
• Endocrine disruption
• Treatment British Anti-Lewisite (BAL)

12

• Cadmium
• Modern toxic metal
• By-product of Zn, Pb mining
• Electroplating, galvanizing
• Paint pigment
• Ni-Cad batteries
• Shellfish, fertilizers, cigarettes
• Toxic Effects Renal Dysfunction
• Accumulates in lysosomes of renal tubules
• Cd2 binds lysozymes impairs resorption
• Also- osteoporosis, incr. blood pressure

13
Mercury Consumption Emissions
NaCl
Hg H2O
NaOH
Cl2
Rayon
PVC
14
Methyl Mercury Bioaccumulation
Anaerobic bacteria
Metallic Hg CH3-Hg
15
Mercury Exposures contam. fish -Minimata,
Japan Hg grain fungicide, Iraq Felt industry
(mad as a hatter) Toxic Effects CH3-Hg
crosses blood-brain barrier De-myelination,
distal neuropathy Numb, tremor, stumbling
gait Metallic mercury
16
Fish Dietary Advisories