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Environmental Health Toxicology

Risk. Risk = probability of suffering harm from hazard.EVERYTHING we do involves some risk.Choices:To smoke or notTo use seat belt or notTo cross street or notThat life is risky is not an issueMaking life choices that manage risk is personal/family/social issue.. 17 June 2010. EnvHealth

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Environmental Health Toxicology

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    1. Environmental Health & Toxicology 17 June 2010 1 EnvHealth&Tox.ppt

    2. Risk Risk = probability of suffering harm from hazard. EVERYTHING we do involves some risk. Choices: To smoke or not To use seat belt or not To cross street or not That life is risky is not an issue Making life choices that manage risk is personal/family/social issue. 17 June 2010 EnvHealth&Tox.ppt 2

    3. Risk Measuring risk. Probability: 0 < P < 1.0 Example: Lifetime Pcancer from exposure to [chemical] = 0.000001 = 1/ 1,000,000 (small risk) Then, in population of USA, about 300 cases/75 years due to this cause 17 June 2010 EnvHealth&Tox.ppt 3

    4. Risk Risk assessment Using data, models to quantify risk. Identifying real or potential hazard Determining probabilities of harm, severity of risk Please list in order of risk severity: homicide automobile accident obesity cancer heart disease smoking (pack/day) airplane crash fire accident at home 17 June 2010 EnvHealth&Tox.ppt 4

    5. Risk Risk assessment Determining probabilities of harm; severity Nature of risk Health risk Environmental risk Economic risk Social impact 17 June 2010 EnvHealth&Tox.ppt 5

    6. Hazards Physical Ionizing radiation, fire, weather, wind, tornado lightening noise, etc. 17 June 2010 EnvHealth&Tox.ppt 6

    7. Hazards Chemical Natural vs. synthetic Water is dangerous in large quantities! Organic, inorganic Pollution air, water, land 17 June 2010 EnvHealth&Tox.ppt 7

    8. Hazards Biological Pathogens, parasites & vectors, Allergens pollen, mold spores, poison ivy Dangerous animals dogs, cattle, horses, snakes wasps, bees jellyfish, Portuguese man-of-war 17 June 2010 EnvHealth&Tox.ppt 8

    9. Hazards Cultural hazards Working conditions, diet, drinking, driving, STDs, poverty, age (?) Exposure to physical, chemical, & biological hazards! 17 June 2010 EnvHealth&Tox.ppt 9

    10. Chemical Hazards 17 June 2010 EnvHealth&Tox.ppt 10 Toxicology: Science that studies effects of poisonous substances on humans and other organisms Any chemical can be harmful “The dose makes the poison.” Toxicity: measure of how harmful [chemical, toxin] is.

    11. Toxicology Whether [chemical] is harmful depends on Quantity ingested, absorbed (dose) Frequency of exposure Who is exposed? gender, age, personal sensitivity, etc. Body’s detoxification systems & health Example: Alcohol 17 June 2010 EnvHealth&Tox.ppt 11

    12. Toxicology Effect = response How much damage done, to what organs? Time frame: Acute effect: immediate, short term Chronic effect: permanent or long-lasting Symptoms may begin immediately, or delayed onset Single toxin may have acute & chronic effects 17 June 2010 EnvHealth&Tox.ppt 12

    13. Toxicology Other factors: Solubility Water soluble Fat soluble Persistence: How long it lasts in body or environment. Excretion = elimination in urine Natural degradability 17 June 2010 EnvHealth&Tox.ppt 13

    14. Toxicology 17 June 2010 EnvHealth&Tox.ppt 14 Other factors: Bioaccumulation: increased concentration in specific tissues over time. Biomagnification: increased concentration up a food web.

    15. Toxicology Three methods, used together, to assess health threat: 1. Case histories 2. Epidemiology 3. Animal testing 17 June 2010 EnvHealth&Tox.ppt 15

    16. Toxicology 1. Case histories Physicians send information of unusual patient complaints/conditions to [agency] (CDC, EPA, county health departments, etc.) 17 June 2010 EnvHealth&Tox.ppt 16

    17. Toxicology 2. Epidemiology Human population studies attempt to correlate exposure (who, state of health, dose & frequency) to occurrence of effects. Limited by low numbers of individuals exposed, genetic & experience variability, other exposures, population movements. 17 June 2010 EnvHealth&Tox.ppt 17

    18. Toxicology 2. Epidemiology Framingham (Mass.) heart study. Severe Acute Respiratory Syndrome (SARS), Fall 2003. Bird flu (avian influenza virus H5N1) direct contact with infected poultry eye infections (conjunctivitis) to severe respiratory disease (pneumonia) to death spread from person to person rare 17 June 2010 EnvHealth&Tox.ppt 18

    19. Toxicology 3. Animal testing Experiments on lab animals determine Toxicity & dose-response curve, Acute or chronic effects, Residence time in body Excretion rate, What tissues & organs affected, How harm occurs. 17 June 2010 EnvHealth&Tox.ppt 19

    20. Toxicology Animal testing Experiments on lab animals determine Toxicity, dose-response curve. Dose-response curve Difficult to use (not a simple science) 17 June 2010 EnvHealth&Tox.ppt 20

    21. Toxicology Dose-response curve Difficult to use (not a simple science) Methodology Usually, experiments use high doses and few (10's - 100's) of test animals. Then, extrapolate to lower doses. 17 June 2010 EnvHealth&Tox.ppt 21

    22. Toxicology Dose-response curve “Linear dose-response model“ No threshold Often assumed in absence of low dose data Saccharin in rats & bladder cancer 17 June 2010 EnvHealth&Tox.ppt 22

    23. Toxicology Dose-response curve “Threshold dose-response model“ Some minimum dose (threshold) below which there is no effect body clears substance without harm. Above threshold dose harm does occur. 17 June 2010 EnvHealth&Tox.ppt 23

    24. Toxicology Extrapolation from animal to human Usually physiology of other mammals is like humans, so rats, mice, dogs, cats, etc. make good surrogates. But, CATS CAN NOT take Tylenol, Aspirin; DOGS can not take chocolate. Then, what can experimental animals tolerate that humans can't ?? 17 June 2010 EnvHealth&Tox.ppt 24

    25. Toxicology Expense of laboratory studies Drug approval by Food & Drug Administration (FDA) takes years, $$. Safety of medicines Effectiveness of medicines Studies of environmental chemicals, biological agents also takes time & money. 17 June 2010 EnvHealth&Tox.ppt 25

    26. Toxicology 17 June 2010 EnvHealth&Tox.ppt 26

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