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.