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Three eras of development of experimental toxicology
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Toxicology Branch
• According to object of study: – Animal Toxicology – Human Toxicology – Plant Toxicology – Insect Toxicology – Livestock Toxicology
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History of Toxicology
• Age of enlightenment: Orfila (1787-1853) – the first toxicologist to use autopsy material and chemical analysis systematically as legal proof of poisoning.
– Introduction of new toxicants and antidotes: nitrite and thiosulfate for cyanide; DDT (1944); organophophorus compounds(1952)
– Development of new branches
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Toxicology - Chaper 1
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Spectrum of Undesired Effects (1)
• Allergic reactions
– Chemical allergy is an immunologically mediated adverse reaction to a chemical and is dose-related for a given individual.
– To identify and understand the cellular, biochemical and molecular mechanisms by which chemicals exert toxic effects on living organisms.
– To design and produce safer alternative chemicals for therapy of poisoning and treatment of diseases.
Oswald Schmiedeberg (1838-1921) – the first
toxicologist to train 120 students who later
populated the most important laboratories of
pharmacology and toxicology throughout the
– Referring to a genetically determined abnormal reactivity to a chemical, i.g., extreme sensitive to low doses or extreme insensitive to high doses.
– Examples of chemical idiosyncrasy include exposures to succinylcholine and methemoglobin-inducing chemicals.
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Spectrum of Undesired Effects (3)
• Immediate versus delayed toxicity
– Most chemicals produce immediate toxic effects but not delayed effects.
• Age of enlightenment: Parcelsus (1493-1548) “All substances are poisons; there is none which is not a poison. The right dose differentiates a poison from a remedy.”
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Toxicology Branch
• According to area of study: – Descriptive Toxicology – Mechanistic Toxicology – Regulatory Toxicology
Toxicology - Chaper 1
Chapter 1
Introduction to Toxicology
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Toxicology
The study of the adverse effects of chemicals on living
organisms and the underlying mechanisms
• Among chemicals there is a wide spectrum of doses needed to produce deleterious effects, serious injury, or death.
• However, the measures of acute lethality such as LD50 may not accurately reflect the full spectrum of toxicity associated with exposure, e.g., carcinogenic or teratogenic effects.
– To establish standards for the amount of chemicals permitted in ambient air, industrial atmosphere, and drinking water.
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Spectrum of Toxic Dose
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History of Toxicology
• Antiquity: Ebers papyrus (1500 B.C.), Ben Chao Gong Mu (Ming dynasty)
• Middle ages: Renaissance - Poisons and Their Antidotes (1198), arsenic-containing products
world.
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History of Toxicology
• Morden toxicology: 1900-
– Development of early advances in analytic methods: heavy metals
– Early mechanistic studies: drugs, plants
– The incidence of allergic asthma has increased substantially in recent years.
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Spectrum of Undesired Effects (2)
• Idiosyncratic reactions
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Toxicology
Like medicine, toxicology is both a science
and an art. The science of toxicology is
defined as the observational and data-
– Neurotoxicology
– Immunotoxicology
– Productive Toxicology
– Hemotoxicolgy
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Toxicology Branch
• According to mechanism of study: – Cellular Toxicology – Molecular Toxicology – Membrane Toxicology – Biochemical Toxicology – Genetic Toxicology
gathering phase, whereas the art of
toxicology consists of the utiloutcomes of exposure in
human and animal population.
Toxicology - Chaper 1
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Toxicology Branch
• According to field of study:
– Environmental Toxicology
– Food Toxicology
– Occupational Toxicology
– Clinical Toxicology
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Toxicology - Chaper 1
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History of Toxicology
• The Silent Spring (Rachel Carson, 1962)
“The earth’s vegetation is a part of a web of life in which there are intimate and essential relations between plants and the earth, between plants and other plants, between plants and animals. Sometimes we have no other choice but to disturb these relationships, but we should do so thoughtfully, with full awareness that what we do may have consequences remote in time and place.”