PHAR 300 POST MT.docx

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McGill University
Pharmacology and Therapeutics
PHAR 300
Edith Zorychta

Routes of exposure • Respiration (breathing)  goes through the lungs • Absorption (skin contact) • Ingestion  through GI tract Toxicant distribution • In all cases, it eventually gets into circulation and carried to individual cells where it causes problems. • In case of exposure through ingestion (GI-tract), you‟ll have direct effects right on the liver as well as the rest of GI-tract before toxicant even reaches circulation. Environmental toxicology This area is gaining more attention and becoming more crucial. We need to think about what we put into the ocean, the air, and the soil. How contaminants in streambed sediment move up the food chain (biomagnification) Toxicants in the air and the soil can eventually end up in the water. What happens afterwards varies among the toxicants. Some stay in the water, some settle down and end up in the sediment at the bottom, and some bio-accumulate. Bio-accumulation: 1. Contaminants are washed into water and build up in the sediment 2. Bottom-dwelling organisms concentrate contaminants and are then eaten by small fish 3. Predator species continue to concentrate toxins by eating those small fish. Large predator species are then consumed by humans Environment affects potential absorption Potential absorption of toxicant does not only depend on its concentration, but the environment in which it is found. If you, for example, put the same mass of toxin A in different environments, the circumstances may affect the amount you‟ll absorb (very little, moderate, or high amounts). This is particularly the case in toxicants dissolved in water because absorption depends on the size/mass of water (pond, lake, or ocean), pH of the water, types of dwellers (plants, organisms that can get rid of toxicants or bio-concentrate them), distribution of toxicants (free-floating or settle-down to sediment), etc. Ex. Biomagnification of DDT (an insecticide) • Assume the concentration of DDT in water is ONE • The concentration of DDT in zooplankton is then 13,000 • The concentration of DDT in minnows is then 170,000 • The concentration of DDT in large fish is then 670,000 • The concentration of DDT in birds is then 8,300,000 • You see incredible biomagnification as you work up through the food chain (biomagnification has significant effect on some of our wildlife). Canadian loons are having difficulties because of this (loons are on loonies, which is the reason why 1$ coin is called loonie) THAT WAS AN OVERVIEW OF TOXICOLOGY
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