Introduction to Toxicology

Toxicology Definition

• Toxicology is derived from two Greek words: toxikon (meaning poison) and logos (meaning study).
• It is the study of the adverse effects of chemicals or poisons on biological systems.
• It involves identifying poisons, understanding their chemical properties, and studying their biological effects.
• Toxicology also includes the treatment of diseases caused by poisons.

Types and Areas of Toxicology

• Descriptive toxicology: Focuses directly on toxicity testing, safety evaluation, and regulatory requirements (e.g., drugs, food additives).
• Mechanistic toxicology: Aims to identify and understand the mechanisms by which chemicals exert toxic effects on living organisms.
• Forensic toxicology: Investigates the medicolegal aspects of chemical harm, primarily in human cases (e.g., post-mortem investigations).
• Clinical toxicology: Focuses on diseases caused by or uniquely associated with toxic substances.
• Environmental toxicology: Investigates the impact of chemical pollutants in the environment on biological organisms, specifically on non-human organisms (e.g., fish, birds, terrestrial animals).

Toxins and Poisons

• Poison: Any solid, liquid, or gas that disrupts cellular life processes, causing physiological or psychological disorders. Synonyms for poison include toxicant.
• Toxin: Substances originating from biological processes (classified as biotoxins). They are capable of causing harmful effects in biological systems.
• Toxicosis: The disease state resulting from exposure to a poison or poisoning and intoxication.

Toxicological Concepts

• Toxicologist: Studies the nature of the adverse effects of toxins at various levels (molecular, cellular, organ, organism, community), understanding how these agents affect systems and how these systems affect the agents.
• Toxicity: The amount of a poison that, under specific conditions, causes toxic effects or detrimental biological consequences. Expressed as milligrams (mg) of toxicant per kilogram (kg) of body weight.
• Dosage: The total amount of toxicant received by a person.

Toxic Agents

• Toxins are often produced by biological sources (plants, animals, fungi, bacteria).
• Toxic agents are classified by various characteristics:
  • Target organs (e.g., liver, kidney)
  • Use (e.g., pesticide, solvent)
  • Origin (e.g., animal, plant)
  • Effects (e.g., cancer, liver injury)
  • Chemical stability or reactivity (e.g., explosive, flammable)
  • Chemical structure (e.g., aromatic amine)
  • Biochemical mechanisms of action (e.g., alkylating agent)
  • Physical state (e.g., gas, dust, liquid)
  • Poisoning potential (ranging from extremely toxic to slightly toxic).

Poisoning Types

• Poisoning: A condition caused by introduction of a substance resulting in ill health or death.
• Four types of poisoning:
  • Accidental: Unintentional exposure (e.g., mishaps at work or school)
  • Suicidal: Intentional ingestion of poisons or overdose of drugs
  • Homicidal: Deliberate killing of a person by another via administration of poison
  • Non-accidental: Exposure (e.g., child abuse) may not present as a clear poisoning, but underlying harm exists.

Poison Classification

• Local action(corrosives): Direct impact on the affected area (e.g., skin irritation, inflammation from strong acids or alkalis).
• Remote action: Poison absorbed into the body, affecting other systems (e.g., alcohol).
• Local and remote actions: Affecting both local and remote organs (e.g., irritant metals, oxalic acid).
• General action: Poison affects more than one body system (e.g., mercury, arsenic).