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![Page 1: Toxicity of metals - chronic health hazards, prevention and surveillance Vesa Riihimäki Unit for toxicological risk assessment Finnish Institute of Occupational.](https://reader030.fdocuments.net/reader030/viewer/2022032600/56649dba5503460f94aaba99/html5/thumbnails/1.jpg)
Toxicity of metals - chronic health hazards, prevention and surveillance
Vesa Riihimäki
Unit for toxicological risk assessment
Finnish Institute of Occupational Health
TYÖTERVEYSLAITOS
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Metals causing harm in the occupational setting
TYÖTERVEYSLAITOS
Aluminium Cadmium Chromium(VI), note: chromium(III) is essential to man Cobolt, note: essential component of B12 vitamin Lead Manganese, note: essential trace element Mercury Nickel Vanadium Zinc, note: essential trace element
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TYÖTERVEYSLAITOS
Occupational exposures to metals
Metal foundry Flame cutting and welding
- stainless steels (Cr, Ni)- special steels (Mn)- cadmium plating- zinc plating- painted steel (Pb)- aluminium
Soldering- silver solder (Cd)- lead solder
Grinding and polishing (Co, Cr, Ni)
Storage batteries- lead- cadmium and nickel- manganese
Instrument repair- mercury
Furnace cleaning- vanadium
Chemicals, catalysts
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Common concepts in metal toxicology
Most metals exhibit limited absorption Metabolism is usually limited to
oxidation/reduction, alkylation/dealkylation or complexation
Many have a long residence time in the body due to binding (sequestering) or storage
Toxicokinetics and target organ toxicity are highly dependent on the metal species
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Species specific metal toxicity
Underlying factors: solubility, uptake (systemic, cellular), tissue distribution, specific biological reactivity
Examples: mercury compounds- metallic mercury- mercuric salts, e.g. chloride- methylmercury- methoxymethylmercury acetate
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Species specific toxicity, cont'd
Aluminium: oxide versus sulphate Chromium(VI) versus chromium(III) Lead dust & salts versus alkyl lead Nickel: metallic Ni, Ni oxides, Ni subsulfide, Ni
carbonyl Zinc: freshly generated fumes of Zn oxide
versus Zn chloride
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Target organs for metals toxicity in humans
Aluminium Kadmium Chromium(VI)
Cobolt Lead
Manganese
CNS, bone Kidney, lung, carcinogenicity Airways, skin, sensitisation,
carcinogenicity, kidney Lung, skin, sensitisation CNS & PNS, blood forming
organs, kidney, reproduction CNS (signs of Parkinsonism)
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Target organs for metals toxicity in humans, cont'd
Mercury- elemental vapour- mercuric salts- alkyls
Nickel
Vanadium Zinc
- CNS, kidney- kidney, skin sensitisation- CNS, developmental toxicity
Airway carcinogenicity, skin sensitisation
Respiratory system Respiratory system
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Tissue distribution and elimination of lead
Central compartment: blood lead- half-time about 30 days- about 4% of the body burden
Soft tissue lead- half-time about 30-40 days- about 2% of the body burden
Lead in bone- half-time up to 30 years- 94% of the body burden
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Physiologically-based toxicokinetic model for lead
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Dose-effect and dose-response relationship: lead decreased erythrocyte delta-ALAD activityincreased zinc protoporphyrin
anemia
CNS effectsdecreased peripheral nerve conductivityNervous paralysis, lead colics
Adapted from Elinder C-G et al., Biologisk monitoring av metallerhos människa. Arbetsmiljöfonden, Uppsala, 1991
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Prevention and surveillance
Control exposure from all sources that may lead to hazardous accumulation
Perform biological monitoring of body burden U-Cr, U-Co, B-Pb, U-Mn (?), U-Hg, U-Ni, U-V to ensure that accumulation will not reach critical levels
Perform health surveillance for early effects, making note of individual susceptibility
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Basis for health surveillance among aluminium welders
Indication of increasing body burden with time at exposure
Suspicion of aluminium accumulation in the target organ of toxicity (the brain)
Demonstration of a dose-response between aluminium in serum and urine and CNS effects (symptoms, attention & working memory impairment, EEG abnormality)
Effect threshold: U-Al 4-6 µmol/l, S-Al 0.25-0.35 µmol/l
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Relationship between aluminium welding months and urinary aluminium concentration
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