ENV HEALTH PG 99-121.docx

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School of Environment
Stephen Scharper

ENV HEALTH PG 99-121  The big killer= tobacco; killed 80mil from1950-2004 19% of cndaian population aged 15 + =smokers in 2007 diseases= heart disease, cancers, bronchitis now teenage girls r smoking more than boys  Risk is the possibility of suffering harm from a hazard that can cause injury, disease, death, economic loss and env damage  Risk assessment= scn process of estimating how much harm a hazard can cause to human health  Risk management involves deciding whether/how to reduce a risk to a certain lvl and at what cost  Harm can come from 4 major hazards: cultural: unsafe working conditions, smoking, poor diet, unsafe sex, pov, assault chemical: air chemicals, water, soil and food physical: radiation, fire, tornado biological: bacteria, viruses, allergies  The harm caused by exposure to a chemical depends on the amount of exposure(dose)  Toxicity measure how harmful a substance is in causing injury, illness or death to a living organism. depends on genetic makeup that determines an individual’s sensitivity  5 factors can affect harm caused by a substance 1-solubility; it can move thru the env and get into water supplies and the aqueous solutions that surround the cells in our bodies Oil-or-fat-soluble toxins=can penetrate the membranes surrounding an organism’s cells bcuz the membranes allow similar oil-soluble chemicals to pass through them they can accumulate in body tissues and cells 2-substance’s persistence; many chemicals are used bcuz of their persistence or resistance to breakdown. they do their job for a long time; but it can also have long lasting harmful effects on the health of ppl 3-Bioaccumulation=accumulation of a substance in the tissue of a single organism 4related factor=Biomagnificationsthe increase in concentration of pollutants such as POPs and heavy metals at higher levels of the food chain 5-chemical interactions that can decrease or multiply the harmful effects of a toxin an antagonistic interaction can reduce harmful effects ex: vitamins e nd a interact to reduce the body’s response to some cancer causing chemicals a synergistic interaction multiplies effects  the effects of exposure to a chemical can be acute or chronic. the type and amount of health damage resulting from exposure to a chemical or other agent is called the response an acute effect is an immediate or rapid harmful reaction stemming from short tern exposure to a potent chemical a chronic effect is a gradual long lasting consequence from long term exposure to a single dose or to repeated sublethal doses of a harmful substance  Every chemical is harmful at some level of exposure ex: drinking 100 cups of strong coffee one after another would expose most ppl to a lethal dosage of caffeine  Your body has 3 major mechanisms for reducing the harmful effects of some chemicals 1 it can break down 2 ; your cells have enzymes that can sometimes repair damage to DNA and protein rd molecules 3 ; cells in some parts of your body can reproduce fast enough to replace damaged cells.  Some ppl also have the mistaken idea that natural chemicals are safe and synthetic chemicals r harmful  The avg person for instance is far more likely to b killed by aflaxatoxin a carcinogen produced by moulds in peanut butter and corn than to b killed by lightning or by a shark.  The 5 top toxic chemicals in terms of human and env health concerns are arsenic, lead, mercury, vinyl chloride and polychlorinated biphenyls  Exposing a population of live laboratory animals especially mice and rats to known amounts of chemical is the most widely used method for determining its toxicity  One method of estimating the relative toxicity of a chemical is to determine its lethal dose  Chronic tests are intended to establish the effect of lower-dose longer-term exposure to the chemical and are run for a longer standard period such as 28 days  Toxicity tests are run to develop a dose-response curve, which shows the effects of various dosages of a toxic agent on a group of test organisms these are controlled experiments in which the effects of the chemical on a test group are compared with the responses of a control group of organisms not exposed to the chemical.  Some scntists challenge the validity of extrapolating data from test animals to humans bcuz human physiology and metabolism often differ from those of the test animals others say it works well and h
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