Chapter_18

Chapter_18 - Chapter18 Toxicology Introduction Toxicology...

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Chapter 18 Toxicology Introduction Toxicology is the study of toxins (poisons), how they damage the body, and how the body can be protected from this damage. Toxins are grouped into classes according to the particular mechanism they use to damage the body. By figuring out the mechanism a particular poison uses to damage the body,
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we can design countermeasures to interfere with this mechanism, and minimize damage to the body.
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DOSAGE Most people who not scientists believe that even small quantities of poisons cause permanent damage to body. In fact, our bodies constantly being attacked by every class of poison that exists, and constantly repairing every kind of damage that poisons can inflict (even cancer). Why then can some poisons kill us or leave us damaged for life? Key to this puzzle involves fact that body has limits on how fast it can repair different kinds of damage. If we ingest large enough quantity of poison in short enough period of time damage repair cannot keep up with speed of poisoning and we die or damaged for life. If drink one beer/day for 60 yrs you ingest 102 gallons of alcohol over lifetime. Drink just one quart of pure alcohol quickly and you die in minutes.
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Show Table 18.2.
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Different poisons have radically different toxic dosage levels. Most common way of expressing killer dosage called the "LD 50 " of the poison. LD 50 ( Lethal Dosage-50%) is dosage which will kill half of people (or test animals) who take that quantity of poison all at once (no repair time). Since big people usually can repair poison damage faster than small people, body weight usually factored out of LD 50 number. You multiply the LD 50 number by your body weight (in kg) to figure out how much poison will have a 50/50 chance of killing you. A person who weighs twice as much can tolerate twice as much poison. LD 50 values vary widely for different kinds of animals. However if LD 50 value extremely low for one animal it's probably safe to assume substance is poisonous for all
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(PROBLEM 6).
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CLASSES OF POISONS I. Corrosives (mechanical) A. Acids B. Bases C. Oxidizers D. Reducing Agents II. Metabolic Poisons (energy) A. Specific Biochemical Inhibitors B. Heavy Metals III.Neurotoxins (nervous system) A. Anticholinesterases B. Acetylcholine Antagonists C. Cell Membrane Disrupters IV.Teratogens (birth defects) V. Mutagens (DNA damage) VI.Carcinogens (cancer) PROBLEM 2. Six classes of toxics?
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@ Corrosives, metabolic poisons, neurotoxins, teratogens, mutagens, and carcinogens.
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ROUTE OF ENTRY How poison gets into body often most important aspect of how poisonous it is. Examples: Water in stomach good; water in lungs poisonous. KCl in food healthy; in blood it's "lethal injection." Three most common routes of accidental entry of poisons into body in order of normal severity of hazard are: 1. Breathing. Substance goes directly (quickly) into bloodstream. 2.
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This note was uploaded on 12/28/2011 for the course CHEM 1002 taught by Professor Staff during the Fall '08 term at LSU.

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Chapter_18 - Chapter18 Toxicology Introduction Toxicology...

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