Lecture_9_Risk_assesment - Toxicology Toxicology...

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Toxicology
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Toxicology Definition: – Study of poisons – “the science which studies toxic substances or poisons, that are substances which cause alteration or perturbation in the function of an organisms leading to harmful effects (Truhaut, 1974)
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Toxicology: assessing chemical hazards (1) How harmful a substance is depends on: Chemical properties of the substance Electronegativity Polarity Oxidation state Molecular weight Dissociation Solubility Water soluble toxins Fat soluble toxins
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Toxicology: assessing chemical hazards (2) • Persistence of chemical • Bioaccumulation • Biomagnification • Chemical interaction – Antagonistic – Synergistic • Multiple chemicals – food additives, pesticides, air pollution Receptor Dose Response
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1. Receptor – organism receiving exposure or dose Frequency of exposure Age General health Genetic makeup Toxicology: Receptor
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2. Dose – the amount of substance a person has Ingested (often greatest source of chemical exposure, 85%) Inhaled (air pollution, particles and volatiles, 10%) Absorbed through the skin (industrial, 5%) Debate about actual amount that receptor site “sees” vs. amount taken in Acute dose – refers to single dose, usually high Chronic dose – repeated or continuous low dose over time Long term – low dose over a life time Toxicology: Dose
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Toxicology: Response 3. Response Nonspecific Burning – destruction of cells caused by exposure to high concentration of strong acids or bases Narcosis – depression in sensory activity, reversible, caused by alcohols, ethers, benzene Specific Damage to excretory organs Damage to respiratory organs Damage to reproductive function Mutagenesis Carcinogenesis Acute toxicity– rapid death Chronic toxicity
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• Every chemical is harmful at some level of exposure • How much exposure causes a harmful response???? • Differently for different individuals • The dose of a usually unknown mixture of chemicals Paracelsus’principle: “The Dose Makes the Poison”
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Measuring manifestations Endpoint - physiological manifestation – Can be readily measured – Use of “biomarkers” e.g. changes in hormone levels, protein markers, enzyme induction
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Methods for determining toxicity – Laboratory experiments on animals (mice and rates)
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This note was uploaded on 04/09/2011 for the course ENVIRONMEN EESA10 taught by Professor Silvajastovenovij during the Spring '11 term at University of Toronto- Toronto.

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Lecture_9_Risk_assesment - Toxicology Toxicology...

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