Toxicology

Toxicology is the study of poisons, the adverse effects of agents on living organisms and a toxicologist studies the nature of those effects and the probability of their occurrence.

Four Divisions of Toxicology

·         Mechanistic Toxicology concerns with the identification and characterization of cellular, biochemical, and molecular mechanisms that are utilized by chemicals to exert toxic effects on living organisms.

·         Descriptive Toxicology uses the results of animal experiments to predict what level of exposure will cause harm in human.

·         Forensic Toxicology concerned with medicolegal consequences of toxin exposure. This area focuses in establishing and validating the analytic performance of the methods used to generate evidence in legal situations, including the cause of death.

·         Clinical Toxicology is the study of interrelationship between toxin exposure and the disease states. This area emphasizes not only diagnostic testing but also therapeutic intervention.

Routes of Exposure

      Ingestion

      Inhalation

      Transdermal absorption

Exposure to Toxins

50% of poisoning cases are intentional suicide attempts, 30% accidental exposure

And the remaining cases are a result of homicide or occupational exposure.

Suicide has the highest mortality rate. Accidental exposure occurs frequently in children and occupational exposure primarily occurs in industrial and agricultural settings.

Toxicants can be classified by system interaction. The most common classifications are:

       Hepatotoxicants -cause damage to the liver (e.g. Acetaminophen, ethyl alcohol)

      Nephrotoxicants -damage to kidneys (e.g. Cadmium, Mercury)

      Neurotoxicants –damage to the nervous system (e.g. lead)

      Immunotoxicants –damage to the immune system (e.g. toluene)

       Hematoxicants –damage to the circulatory system (e.g. Benzene)

      Dermatoxicants- damage to the skin (e.g. Magnesium Chromate)

   Pulmonotoxicants –damage to the lungs (e.g. Asbestos)

      Carcinogens –agents that increase cancer risk (e.g.  Hexavalent chronium)

 Toxicology: Common Drugs and their effects to the body

Toxicity Rating System

Toxicity Rating	Lethal Oral Dose in Average Adult
Super toxic	<5mg/kg
Extremely toxic	5-50 mg/kg
Very toxic	50-500 mg/kg
Moderately toxic	0.5-5 g/kg
Slightly toxic	5-15 g/kg
Practically nontoxic	>15 g/kg

 

Acute and Chronic Toxicity are terms used to relate the duration and frequency of exposure to observed toxic effects.

Ø  Acute Toxicity is usually associated with a single, short term exposure to a substance

Ø  Chronic Toxicity is usually associated with repeated frequent exposure for extended periods, at doses that are insufficient to cause an immediate acute response.

References:

Michael Bishop et al Clinical Chemistry Techniques, Principles, Correlations 6^th Edition

William E. Luttrell et al Toxicology Principles for the Industrial Hygienist