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• Toxicology


  The study of poisons
• Poison


  A substance capable of producing adverse effects on an individual under appropriate conditions
• World Health Organization toxicity classes


  • Class I - a: extremely hazardous (e.g. cisplatin, doxurubicin)
  • Class I - b: highly hazardous (e.g. methotrexate)
  • Class II: moderately hazardous (e.g. NSAIDs)
  • Class III: slightly hazardous (e.g. paracetamol)
• Toxins


  Substances that are produced naturally (nature origin) capable of causing adverse effects on other organisms
• Toxicity


  Degree to which a substance is poisonous or can cause injury
• Toxic agent


  Anything that can produce an adverse biological effect, it may be chemical, physical, or biological
• Toxicant


  A chemical that can injure or kill humans, animals, or plants
• Examples of toxicants


  • Pesticides
  • Benzene
  • Asbestos-like fibers such as carbon nanotubes
• Routes of exposure of toxins


  • Skin
  • Ingestion
  • Lungs
• Dose


  An important factor in toxicology, the principle "the dose makes the poison" coined by Paracelsus
• LD50


  Dose of a substance that displays toxicity in that it kills 50% of a test population, a measure of how toxic a substance can be
• LC50


  Lethal concentration of a substance that can cause 50% deaths when exposed to a population, a measure used to assess toxicity
• Importance of studying toxicology


  • Provides protection to humans and environment from toxic effects of toxicants
  • Leads to development of newer, innovative and more selective drug therapies with reduced toxic potential
• Branches of toxicology


  • Analytical
  • Applied
  • Clinical
  • Veterinary
  • Environmental
  • Industrial
  • Immuno
  • Reproductive and Developmental
• Toxicology


  Derived from the Greek words "toxikon" meaning poisonous substance and "logos" meaning study
• In ancient times (1500 BC), the earliest collection of medical records contained many references and recipes for poisons
• Dioscorides, a Greek physician, classified poisons as animal, plant or mineral and recognized the value of emetics
• Maimonides wrote about poisons and their antidotes in "The Book of Poisons and Their Antidotes"
• Paracelsus


  The "father of toxicology", first to use minerals and other chemicals in medicine
• Animal venom and plant extracts were widely used as poisons in earlier times
• The Ebers Papyrus contained information on many recognized poisons, including hemlock, aconite, opium, and metals
• Opium


  A highly addictive non-synthetic narcotic extracted from the poppy plant, containing alkaloids like morphine, codeine, and thebaine
• The Ebers Papyrus was written in 1550 BCE using 328 different ingredients (most derived from plant species) to make 876 prescriptions
• Hippocrates added a number of poisons and clinical toxicology principles pertaining to bioavailability in therapy and overdosage
• Theophrastus, a student of Aristotle, included numerous references to poisonous plants in "De Historia Plantarum"
• Dioscorides made the first attempt to classify poisons, accompanied by descriptions and drawings
• Socrates was executed by drinking a cup of hemlock extract
• Demosthenes took poison hidden in his pen, and Cleopatra used the asp as a method of suicide
• The Romans made considerable use of poisons in politics, and King Mithridates VI of Pontus conducted acute toxicity experiments on criminals
• The Lex Cornelia was the first law against poisoning, enacted by Lucius Cornelius Sulla around 81 BCE
• Toxicology evolved rapidly during the 1900s, with the exponential growth of the discipline traced to the World War II era
• Hazard


  A potential source of danger or harm
• Risk


  The likelihood that harm from a specific hazard will occur
• Risk assessment


  The formal process of quantifying risk based on known hazards and the amount of exposure
• Risk assessments are typically done for specific types of exposure scenarios
• Asbestos is a naturally occurring mineral that was once widely used in construction materials due to its heat resistance and insulating properties
• Occupations with high asbestos exposure include construction workers, demolition crews, and firefighters, and asbestos-containing materials in older buildings can also pose a risk
• Inhalation of asbestos fibers can lead to serious respiratory conditions such as asbestosis, lung cancer, and mesothelioma
• Risk assessment/risk management framework


  • Hazard identification
  • Dose-response assessment
  • Exposure assessment
  • Risk characterization
• Structure-activity relationships (SAR)


  Studying the relationship between the chemical structure of a substance and its biological or toxicological activity