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112. Occupational toxicology, chemical safety

  • Occupational toxicology
    • The maximum working time in occupational exposure to hazardous compounds is:
      • 8 hours per day, 5 days per week, 240 shifts per year
    • Measurement of toxicity – by LD50 (the dose which kills 50%)
    • Toxicity according to timeframe
      • Acute toxicity – within 24 hours
      • Subacute toxicity – between 24 hours and 90 days
      • Chronic toxicity – later than 90 days
    • Elimination of organic toxic materials
      • Phase 1 of biotransformation – oxidation
        • By CYP450
      • Phase 2 of biotransformation – conjugation with glucuronic acid, acetyl, etc.
      • Phase 3 – excretion by kidney or liver
    • Elimination of heavy metals
      • Phase 1 – expression of metallothionein genes
        • These genes code for proteins which bind to the heavy metals
      • Phase 2 – excretion or storage of the metal-protein complex
    • Pesticides
      • Used in agriculture, wood preservation, pest control, over the counter, etc.
      • Occupational exposure
        • Pesticide synthesis workers
        • Agricultural workers
        • Pest control workers
      • Absorbed through skin, respiratory tract, GI tract
      • Persist for many months in the body
      • Examples
        • Organophosphates – Irreversibly inhibit acetylcholinesterase – cause cholinergic crisis
        • N-methyl carbamates – reversible inhibit acetylcholinesterase
        • DDT – a volatile organic compound (VOC)
  • Chemical safety
    • The CAS registry
      • A registry which contains every chemical substance known
      • Contains information about the substances
      • Currently contains more than 150 million
    • Material safety data sheet
      • Follows all dangerous chemicals
      • Provides all relevant information, like possible hazards, how to handle safely, etc.
      • European hazard symbols
        • Used until 2015 – nowadays the Globally Harmonised System is used instead
        • E – explosive
        • F – highly flammable
        • O – oxidizing
        • T – toxic
        • Xn – harmful
        • Xi – irritating
        • C – corrosive
        • N – dangerous for the environment
    • R phrases (risk phrases)
      • Codes which correspond to specific risks
      • R1 – explosive when dry
      • R45 – may cause cancer
      • etc.
    • S phrases (safety phrases)
      • Codes which correspond to specific safety rules
      • S24 – avoid contact with skin
      • Etc.