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Toxicology• Toxicology—measure of how armful a
substance is– Potential harm is dependent on
• Dosage• Bioaccumulation—some molecules are absorbed
& stored in specific organs or tissues at levels higher than normally would be expected
• Biomagnification—levels of some toxins in the environment are magnified as they pass through a food web– DDT, PCBs, & some radioactive isotopes
• Chemical interactions that can decrease or multiply the effects of a toxin
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Toxicology
• Antagonistic interaction—reduce the harmful response– Vitamins A & E interact to reduce body’s response
to carcinogens• Synergistic interaction—multiplies harmful
effects– Asbestos increase chances of lung cancer– workers who smoke increase chances of lung
cancer 400x
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Toxicology• Poison—chemical that has an LD50 of 50 mg or
less per kg of body weight– LD50—median lethal dose• The amount of chemical that in one dose that kills
exactly 50% of the animals in a test population within a 14 day period
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Toxicology
• Toxicity Testing– Dose-response curves—shows the effects of various
dosages of a toxic agent on a group of test organisms• X-axis plot concentration of toxin & y-axis plots response• Usually follows an S-shaped curve
• Epidemiology—study of the patterns of disease or other harmful effects from toxic exposure within defined groups of people to figure out why some people get sick and other do not
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Chemical hazards• Toxic chemicals—substances that are fatal to
more than ½ of test animals (LD50) at given concentrations
• Hazardous chemicals—cause harm by being flammable, irritating or damaging to skin or lungs, interfering with oxygen uptake, or inducing allergic reactions
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Chemical Hazards
• Mutagens—agents that cause random mutations to DNA molecules– Most mutations are harmless due to repair mechanisms
• Teratogens—chemicals, radiation, or viruses that cause birth defects while the human embryo is growing & developing during pregnancy– PCBs, thalidomide, steroid hormones, arsenic, cadmium, etc.
• Carcinogens—chemicals, radiation, or viruses that cause or promote the growth of malignant tumors in which cells multiply uncontrollably
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Chemical Hazards• Effects of Chemicals on Human Body Systems– Immune system—HIV, ionizing radiation, malnutrition, &
synthetic chemicals
– Nervous system—Neurotoxins• Chlorinated hydrocarbons (DDT, PCBs, dioxins)• Organophosphate pesticices• Formaldehyde• Chemicals of arsenic, mercury, lead, & cadmium• Industrial solvents (toluene, xylene)
– Endocrine system—synthetic chemicals called hormonally active agents disrupts effects of hormones
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Biological Hazards• Nontransmissible Diseases—not caused by
living things & do not spread from person to person– Cardiovascular diseases, cancers, diabetes, etc
• Transmissible diseases—caused by living things and can be spread from person to person
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Biological Hazards
• Pathogens are spread via air, water, food, body fluids, insects
• WHO’s seven deadliest infectious diseases– Acute respiratory infections (pneumonia & flu)—3.7 million/yr– HIV/AIDS—2.6 million/yr– Diarrheal diseases—2.5 million/yr– Tuberculosis—2 million/yr– Malaria—1.5 million/yr– Measles—1 million/yr– Hepatitis B—1 million/yr
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Biological Hazards
• Treatments for infectious diseases– Bacterial & protozoan diseases are treated with
antibiotic drugs– Viral disorders are treated with vaccines before
infection
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Biological Hazards
• Factors affecting the spread of transmissible diseases– Increased international air travel– Migration to urban areas– Migration to uninhabited rural areas & deforestation of
tropical developing nations– Hunger & malnutrition– Increased rice cultivation (mosquito breeding)– Global warming– High winds or hurricanes– Accidental introduction of insect vectors– Flooding
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Biological Hazards• Epidemiological transition—infectious
diseases of childhood become less important and the chronic diseases of adulthood become more important in causing mortality– Infectious & parasitic diseases cause 43% of
deaths in developing nations but only 1% in developed nations