toxicology

• Toxicology


  The science that deals with the adverse effects of chemicals on living organisms and assesses the probability of their occurrence
• Disciplines of modern toxicology

  • Mechanistic toxicology
  • Clinical toxicology
  • Descriptive toxicology
  • Regulatory toxicology
  • Forensic toxicology
  • Environmental toxicology
• Mechanistic toxicology


  Investigates how a chemical causes toxic effects by examining its absorption, distribution and excretion
• Clinical toxicology


  Investigates the toxic effects of various drugs in the body and the treatment and prevention of drug toxicity in the population
• Descriptive toxicology


  Investigates the toxic properties of chemical agents for various endpoints using a variety of different organisms
• Regulatory toxicology


  Uses scientific data to determine how to protect humans and animals from excessive risk
• Forensic toxicology


  Uses medical evidence of poisoning, and tries to establish the extent to which poisons were involved in human deaths
• Environmental toxicology


  Investigates the effects of pollutants on organisms, populations, ecosystems and the biosphere
• China (plant and fish poisons)

  2700 B.C.
• Egypt (800 poisonous recipes)


  1900-1200 B.C.
• India (poisons and antidotes)

  800 B.C.
• Greece (600 plant and mineral poisons)

  50-100 A.D.
• Romans (poisons for executions)

  50-400 A.D.
• Islamic authority on poisons

  980-1036 A.D.
• Paracelsus (the father of toxicology)


  1493-1541
• Paracelsus: '"All substances are poisons: there is none which is not a poison. The right dose differentiates a poison from a remedy."'
• Ramazzini (Book; Diseases of Workers)


  1713
• Orfila (Toxicology as a distinct discipline)


  1815
• Paul Ehrlich – developed staining procedures to observe cell and tissues of how toxicants influence living organisms


  1936
• Exposure


  Must occur first for the chemical to present a risk
• Risk


  The magnitude of risk is proportional to both the potency of the chemical and the extent of exposure
• Dose makes the poison

  The amount of the chemical at the target site determines the toxicity
• Poisonous chemicals


  Plants, animals and bacteria
• Toxicant


  Specific poisonous chemicals
• Phytotoxins


  Toxins from plants
• Zootoxins


  Toxins from animals
• Bacteriotoxins


  Toxins from bacteria
• Xenobiotic


  Man-made substance
• Toxicity


  The adverse effects that a chemical may cause
• Dose


  The amount of chemical that accesses the body
• Exposure


  The extent to which a poisonous dose is acquired
• Hazard


  The likelihood that a toxicity will be expressed
• Antidotes


  Counteracting a poison
• Types of antidotes


  • Chemical - reacts chemically with the poison to form a harmless compound
  • Mechanical - prevents absorption (activated charcoal)
  • Physiological - counteracts the effects of the poison by producing opposite physiological effects
• LD50


  The amount (dose) of a chemical which causes death in 50% of a population of test animals, to which it is administered by any of a variety of methods
• LC50


  The concentration of a chemical in an environment (generally air or water) which causes death in 50% of an exposed population of test animals in a specified time frame
• Dose (mg/kg/day)


  % Adverse Outcome
• Sugar has an LD50 of 30,000 mg/kg
• Ethanol has an LD50 of 13,700 mg/kg
• Water has a recognized LD50 of 80,000 mg/kg