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Introduction to Toxicology

Objectives

  • Appreciate that all substances are potentially toxic
  • Have a basic understanding of the scope of toxicology
  • Appreciate that many scientists, technicians, clinicians, and regulators are concerned with toxic chemicals
  • Understand there are different fields and applications of toxicology and different aims and approaches when dealing with toxic chemicals and effects

The scope of toxicology

Toxicology is the study of the harmful effects of chemicals on living organisms. Toxicology is a branch of pharmacology, dealing with the origin, nature, chemistry and adverse effects of chemical substances. 
Toxicology is the study of harmful effects of chemicals on living organisms, including the origin, nature, chemistry & adverse effects of chemical substances
Potentially toxic substances include:
  • Food
  • Drinking water
  • Air
  • Medications
  • Cosmetics
  • Bites and Stings
  • Venomous animals and plants 

 Today, much knowledge of toxic substances comes from lab-based experiments using animals, tissue cultures or bacteria and human data from accidental poisonings, drug use and industrial use of chemicals. Workers exposed to chemicals include pesticides, solvents, pigments, mineral dust etc.
Occupational dematoses, ailment and respiratory diseases such as silicosis and asbestosis still remain serious problems today. 
The main aim of toxicology is to assess the toxicity of chemicals so they can be used in appropriate and safe ways. All chemicals, whether natural or synthetic are potentially toxic if the dose is sufficient.

Just about everything is toxic if the dose is sufficient.

All the following toxins are poisonous:
  • Cyanide
  • Arsenic
  • Common salt
  • Water (intoxications)
  • Oxygen (Increased free radicals leading to cellular damage)
Water in excessive amounts can be toxic (even fatal) because if it disturbs the electrolyte balance and causes osmotic pressure changes.

Water intoxication symptoms include:
  • Confusion
  • Disorientation
  • Changes in mental state
  • Psychotic symptoms
  • Hypotremia
  • Nausea and vomiting
  • Disturbance in electrolyte balance
  • Decreased sodium concentration
  • Eventual death
Brain effects caused by movement of water into brain cells in response to extracellular osmolarity. Symptoms become apparent when sodium levels fall below 120mmol/L. Severe symptoms occur when very low sodium concentrations of 90-105mmol/L



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