Chapter 12 Human Health Risk

1. I wish I could do that.. Chapter 12 Human Health Risk

2. Hi everybody! LAST surprise in class opinion paper (ha!) will be…… Thursday!

3. Where We’re going • First, a bit of perspective on health hazards • We’re only going to hit the high points, and some information about how we determine hazards. • Some of this chapter won’t be testable, so look for the Study guide for what to learn. • We’ll focus most on anthropogenic chemical hazards

4. Two important facts • Life expectancy has been rising • Mortality rate of the human race remains stubbornly at 100%. • So any discussion about hazards occurs with this as the background

5. Human health is affected by a large number of risk factors.

6. Three Categories of Human Health Risks • physical • biological • chemical

7. Three Categories of Human Health Risks Physical risks include: • natural disasters • accidents • excessive radiation exposure from radon, x-rays, or sunlight

8. Three Categories of Human Health Risks Biological risks are associated with disease- usually infectious disease. • Disease is any impairment of body functions with a characteristic set of symptoms and signs.

9. Three Categories of Human Health Risks Chemical risks are associated with excessive exposure to: • Naturally occurring chemicals (lead, arsenic) • Chemicals from anthropogenic sources (pesticides, solvents)

10. Leading Causes of Death in the World For some reason, growing old and dying isn’t on the chart How do you think this has changed in the last, say, 150 years?

11. http://boingboing.net/2012/06/27/causes-of-death-1900-and-2010.htmlhttp://boingboing.net/2012/06/27/causes-of-death-1900-and-2010.html

12. Biological Risks • Infectious diseases: those caused by infectious agents, known as pathogens • Examples: pneumonia, typhoid, polio, venereal diseases (STDs), HIV, tetanus, malaria, yellow fever, influenza, parasitic worms

13. Biological Risks Diseases fall into two categories: • Chronic diseases:slowly impair the normal functioning of a person’s body • Acute diseases: rapidly impair the normal functioning of a person’s body

14. Leading Health Risks in the World:Low vs. High-Income Countries

15. Infectious diseases have killed large numbers of people.

16. Historically Important Infectious Diseases • Plague • Malaria • Tuberculosis

17. Historically Important Infectious Diseases Plague: also called “bubonic plague” or “Black Death” • Caused by bacterium Yersinia pestis • Spread by fleas associated with rodents, particularly rats • Killed hundreds of millions of people prior to the 20th Century

18. Historically Important Infectious Diseases Malaria is another historical killer of many millions of people. • Still infects hundreds of millions of people today. • An estimated one million people (mainly children) die from it each year. • Malaria is expected to spread and return to many regions as global warming increases.

19. Historically Important Infectious Diseases • Malaria is caused by one of several species of Plasmodium, a protist. • Life cycle includes incubation and transmission inside a mosquito. • Was only eradicated from the United States in 1951. • No vaccine exists against malaria.

20. Historically Important Infectious Diseases Tuberculosis: caused by Mycobacterium tuberculosis • Historically active across the globe • Spread by infected people through coughing or contact with infected sputum (e.g., on an unsanitized common drinking cup at a well)

21. Historically Important Infectious Diseases • Tuberculosis is estimated to currently infect one-third of the world’s population • Public health measures have greatly reduced the rate of infection • Can be cured by antibiotics but this can be long-term and sometimes expensive • Drug-resistant strains have evolved in recent years

22. Emergent Diseases • HIV/AIDS • Ebola • Mad Cow Disease • Bird Flu • West Nile Virus

23. Emergent Diseases • HIV/AIDS: viral disease can be communicated by blood and other body fluids. • Perhaps the most significant of the newly emergent diseases. • Over 33 million are now infected with HIV, and 25 million people have died from AIDS. • While combinations of drugs can significantly prolong life, such treatment is expensive. • Less-developed nations in Africa have significant numbers of HIV-positive people.

24. Emergent Diseases • Ebola: a rare virus found in central Africa. • No major epidemics yet, but no vaccine or treatment exists for Ebola. • Mad Cow Disease: caused by poorly understood proteins (prions) and can be transmitted by eating parts of the central nervous system of infected cattle. • Mad Cow Disease is controlled by strict regulation of meat supply.

25. Emergent Diseases • Bird Flu: avian disease caused by H1N1 virus which killed 100 million people in 1918 (Spanish Influenza). • A modern variant form of avian flu, the H5N1 virus infects people and also has the potential to kill millions if it spreads. • West Nile Virus: lives in hundreds of species of birds and is transmitted by mosquitoes. • West Nile Virus has spread to the United States and has infected and killed people.

26. Pathways of transmitting pathogens

27. Toxicology is the study of chemical risks.

28. Chemical Risks • Neurotoxins: chemicals that disrupt the nervous system (insecticides, lead, mercury) • Carcinogens: chemicals that cause cancer through inflicting damage to cells (tobacco smoke, asbestos, radon) • Teratogens: chemicals that interfere with the normal development of embryos or unborn babies(alcohol, some medications)

29. Chemical Risks • Allergens: chemicals that cause allergic reactions, some of which are serious and potentially fatal (nuts, penicillin, animal dander) (Biological??). • Endocrine disruptors: chemicals that interfere with the normal functioning of hormones in an animal’s body. • Hormonal wastes have affected fish and amphibian reproduction, and may affect humans.

30. Scientists can determine the concentrations of chemicals that harm organisms.

31. Dose-ResponseStudies • LD50:lethal dose that kills 50% of the individuals. • Determines relative toxicity of a chemical. • LD50 varies greatlyamong species for a given chemical. • Why not LD100?

32. Dose-ResponseStudies • When other harmful effects not leading to death are studied, a different measurement is used, ED50. • ED50:effective dose that causes 50% of the animals to display the harmful but nonlethal effect(s).

34. Dose-ResponseStudies • Acute studies: are short term and last only a few days. • Chronic studies: attempt to observe effects of longer-term exposure to a chemical, sometimes at low dosages.

35. Epidemiological Studies • Epidemiology is a field of science that seeks to study causes and patterns of disease in animal and human populations. • Epidemiology uses retrospective and prospective studies.

36. Retrospective and Prospective Studies • Retrospective studies monitor populations who have been exposed to a chemical at some time in the past, and looks for possible effects. • Prospective studies monitor populations that might become exposed to chemicals sometime in the future.

37. Synergistic Interactions • Synergistic interactions: when two risks together cause more harm that one would alone. • For example: the health impact of a carcinogen such as asbestos can be much higher if an individual also smokes tobacco, demonstrating a synergistic interaction.

38. Routes of Exposure

39. Bioaccumulation • Bioaccumulation: an increased concentration of a chemical within an organism over time.

40. Biomagnification Biomagnification: the increase in a chemical concentration in animal tissues as the chemical moves up the food chain.

41. Persistence Persistence: how long a chemical stays in the environment This is an example of manipulating the data- Roundup’s ALL GONE in soil in 1 DAY!- and that’s where it’s applied!

42. Risk analysis helps us assess, accept, and manage risk.

43. Risk Analysis

44. Perceived versus Actual Risk The perception that certain behaviors or activities entail a high risk does not always reflect reality (the actual risk).

45. Perceived versus Actual Risk • Compare the risk to life of crossing the United States (1) riding in an automobile (2) flying on an airplane for a scheduled commercial flight • The actual risk to lifeis much, much lower for flying.

46. Getting killed by a deer >> many other risks

47. Qualitative Risk Assessment • Qualitative: making a judgment concerning the perceived relative risks of various decisions or behaviors • Probability: the statistical likelihood of an event actually occurring and the likelihood of that event causing harm

48. Quantitative Risk Assessment The approach to calculating a quantitative risk assessment is: Risk= (probability of exposure to a hazard) × (probability of being harmed if exposed)

49. Two Philosophies of Risk Assessment and Management • Innocent-until-proven-guilty principle: a product or service poses an unacceptable risk only if proven so in practice or by research. • Precautionary Principle: if a hazard is plausible but not proven, steps must be taken to reduce or remove the hazard.

50. Stockholm Convention • In 2001, a group of 127 nations met in Stockholm to reach an agreement to restrict global use of some chemicals. • Twelve chemicals (“the dirty dozen”) were to be banned, phased out, or reduced. • These include DDT, PCBs, and certain chemicals that are by-products of manufacturing processes.