Week 10 Lecture

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University of Toronto Scarborough
Environmental Science
Jovan Stefanovic

Toxicology 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) Poisons are compounds and cause negative impacts on human health Subject of research in toxicology: from the sources of these poisons, the composition, the partition in the environment, exposure (how someone gets exposed to this), from which source, how much (dose), what kind of response human body can have, chemistry of the poison Toxicology: assessing chemical hazards (1) How harmful a substance is depends on: Chemical properties of the substance Electronegativity Polarity water is polar (has negative and positive side), all chemicals that are polar dissolve well in water While non-chemicals are not dissolvable in water Relates polarity to solubility Polar chemicals mostly stay between the cells in human tissues, they are not able to penetrate through the cell walls because they have fats (non-polar) While the non-polar chemicals are soluble in fats, they are able to go through the cell wall and enter the cell Oxidation state Molecular weight Dissociation Solubility Water soluble toxins Fat soluble toxins Toxicology: assessing chemical hazards (2) Persistence of chemical (i.e. DDT we want to have a prolong effect of DDT to protect the crops, but from an environmental perspective, persistence is not something we preferlike) Bioaccumulation = chemicals accumulate in particular tissues in the human body (muscles, brain, hair) Biomagnification = building up the level of the chemical in the food chain (i.e. animals at the top of the food chain are the highest to have the highest level of chemicals in their bodies) Chemical interaction (chemicals are always exposed to more than one chemical at the same time, interaction can reduce or increase toxicity) Antagonistic = when one chemical reduces the toxicity of another one Some vitamins (A and E) may reduce human reaction to some carcinogens Synergistic = when two chemicals are together, one of them become more toxic E.g. smoking in the presence of asbestos Multiple chemicals food additives, pesticides, air pollution Receptor Dose www.notesolution.com
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