Environmental Hazards and Human Health

1. Environmental Hazards and Human Health Chapter 17

2. Core Case Study: The Global HIV/AIDS Epidemic • Acquired immune deficiency syndrome (AIDS) caused by human immunodeficiency virus (HIV);many secondary infections • No vaccine to prevent or cure AIDS • Expensive drugs—live longer • 30 Million deaths, so far (as of Dec. 2010); alter country’s age structure

3. Global Outlook: Worldwide, AIDS Is the Leading Cause of Death for Ages 15–49 Gapminder.org Life expectancy + %HIV infection

4. 17-1 What Major Health Hazards Do We Face? • Concept 17-1 People face health hazards from biological, chemical, physical, and cultural factors, and from the lifestyle choices they make.

5. Risks Are Usually Expressed as Probabilities • Risk – likelihood something will cause harm • Probability (likelihood) and possibility (could happen) • Risk Assessment – using statistics to estimate how much harm a hazard can cause • Risk Management – making decisions to minimize risk

6. Watch out for anecdotal evidence… • “My teacher never smoked a day in his life and got lung cancer.” • “My grandmother smoked 2 packs a day and didn’t get lung cancer.” • Both cases are possible. The first case is not as probable. One in 6,250 nonsmokers die of lung cancer, whereas one in 250 smokers will die of lung cancer.

7. Science: Risk Assessment and Risk Management

8. We Face Many Types of Hazards • Five major types of hazards • Biological: pathogens (virus, bacteria, fungi, parasites, protozoa) • Chemical • Physical • Cultural • Lifestyle choices

9. 17-2 What Types of Biological Hazards Do We Face? • Concept 17-2 In terms of death rates, the most serious infectious diseases are flu, AIDS, diarrheal diseases, malaria, and tuberculosis; most of these deaths occur in developing countries.

10. Some Diseases Can Spread from One Person to Another • Nontransmissible disease (non-pathogenic, non-transmissible) • Infectious disease (caused by pathogens) • Transmissible disease (contagious or communicable disease) • Since 1950, death from infectious diseases have declined due to: • Better health care • Antibiotics • Vaccines • Disability-adjusted life years (DALYs = YLL+YLD)

11. Major Causes of Death in the World and in the United States in 2005 Why is our cancer % higher than average?

12. Infectious Diseases Are Still Major Health Threats • Infectious diseases spread through • Air • Water • Food • Body fluids • Epidemics and pandemics • Resistance of bacteria and insects

13. Science: Pathways for Infectious Diseases in Humans Self-Study

14. The World’s 7 Deadliest Infectious Diseases Kill 12.5 Million People What is MDR TB?

15. Science Focus: Genetic Resistance to Antibiotics Is Increasing • Bacteria: rapid reproduction, easily spread • Over use of antibiotics • Over use of pesticides • Methicillin-resistant Staphylococcus aureus (MRSA) • Resistant to most antibiotics • Symptoms of MRSA • How will it be controlled? Self-Study

16. Case Study: The Growing Global Threat from Tuberculosis • Why is tuberculosis on the rise? • Not enough screening and control programs • Genetic resistance to a majority of effective antibiotics • Person-to-person contact has increased • AIDS individuals are very susceptible to TB Self-Study

17. Some Viral Diseases Kill Large Numbers of People (1) • Influenza or flu virus • #1 Killer • Transmission – body fluids or airborne emissions • HIV • #2 Killer • Antiviral drugs – slow the progress, but cost a lot

18. Some Viral Diseases Kill Large Numbers of People (2) • Global strategy to slow down the spread of HIV • Reduce the number of new infections • Concentrate on those most likely to spread HIV • Free testing • Education for prevention • Provide free or low-cost drugs • Research

19. Some Viral Diseases Kill Large Numbers of People (3) • Hepatitis B virus (HBV) • #3 Killer • Mode of transmission • Viruses that move form animals to humans • West Nile virus • Severe acute respiratory syndrome (SARS) • Reduce chances of infection: Wash your hands • (why are hand sanitizers bad? When are they good?)

20. Tracking the Spread of Infectious Diseases to Humans from Other Animals • Ecological medicine • Human practices that encourage the spread of diseases from animals to humans • Emerging infections • HIV • SARS • West Nile virus • Lyme virus

21. Case Study: Malaria—Death by Parasite-Carrying Mosquitoes (1) • Malaria • Caused by Plasmodium sp. carried by Anopheles mosquitoes • Spread • Symptoms • Malarial cycle • Malaria on the rise since 1970 • Drug resistant Plasmodium • Insecticide resistant mosquitoes • Effect of global warming • AIDS patients particularly vulnerable • Prevention of spread and current research Malaria video See also videos in APES file.

22. Global Outlook: Distribution of Malaria and Mosquito nets

23. We Can Reduce the Incidence of Infectious Diseases • Good news • Vaccinations on the rise • Oral rehydration therapy • Bad news • More money needed for medical research in developing countries

24. Why help “them”, again?? • Let’s revisit semester 1 • Human population is changing ______________ • HIPPCO stands for____________ • Should we work to increase life expectancies? • Would that increase the total population further? • What about demographic transition?

26. Solutions: Infectious Diseases, Ways to Prevent or Reduce Their Occurrence Self-Study

27. 17-3 What Types of Chemical Hazards Do We Face? • Concept 17-3 There is growing concern about chemicals that can cause birth defects and cancers and disrupt the human immune, nervous, and endocrine systems.

28. Some Chemicals Can Cause Cancers, Mutations, and Birth Defects • Toxic chemicals • Carcinogens • Mutagens • Teratogens

29. Is molecular shape really important?! YES! • Thalidomide is an unfortunate example.

30. Thalidomide has two forms:

31. Thalidomide seemed great… • It was used as • a sleep aid • an anti-emetic (helps with nausea). • for other diseases

32. It passed testing • It was never approved by the US FDA. But in many other countries • It caused no problems in mice, rats, dogs • It was even tested on pregnant rats • There seemed to be no negative affects.

33. Thalidomide was given to pregnant women. • In the first three months of pregnancy, many women have nausea and vomiting. • Thalidomide was given and worked great to stop this “morning sickness”.

34. Birth defects occurred. • When the babies were born, many had severe birth defects. • These resulted in shortening of the long bones of the arms and/or legs.

36. More testing was done. • Testing was done on pregnant primates. The same birth defects occurred. • The FDA had required some drugs to be tested on a primate, before humans, but no longer does. Is that a good thing?

37. So what happened? • There are two forms of the drug. • One has no negative affects. • One is teratogenic. • The two forms are both formed during synthesis, but could be separated. • What’s the difference between the two forms? Only a minor difference in shape.

38. Case Study: PCBs Are Everywhere—A Legacy from the Past • Class of chlorine-containing compounds • Very stable • Nonflammable • Break down slowly in the environment • Travel long distances in the air • Fat soluble • Biomagnification • Food chains and webs • Banned, but found everywhere

39. Potential Pathways on Which Toxic Chemicals Move Through the Environment

40. Some Chemicals May Affect Our Immune, Nervous, and Endocrine Systems (1) • Some natural and synthetic chemicals in the environment can weaken and harm • Immune system • Nervous system • Endocrine system

41. Some Chemicals May Affect Our Immune, Nervous, and Endocrine Systems (2) • Hormonally active agents (HAAs) • Gender benders • Thyroid disrupters • Toxic chemicals • Phthlates • Effects on the endocrine system • Cancer

42. Science Focus: Mercury’s Toxic Effects (1) • Hg: teratogen and potent neurotoxin • Once airborne, persistent and not degradable • 1/3 from natural sources • 2/3 from human activities • Enters the food chain: biomagnification Self-Study

43. Science Focus: Mercury’s Toxic Effects (2) • 2007: Hg hotspots identified • How are humans exposed? • Inhalation: vaporized Hg or particulates of inorganic salts • Eating fish with high levels of methylmercury • Effects of Hg on humans • Who is most at risk? Self-Study

44. Science: Cycling of Mercury in Aquatic Environments Self-Study

45. Solutions: Mercury Pollution Self-Study

46. Hormones and Hormones Mimics or Blockers

47. Science Focus: Bisphenol A • Estrogen mimic • Found in many common products • Laboratory findings • Effects on human health • Should it be banned? Self-Study

48. 17-4 How Can We Evaluate and Deal with Chemical Hazards? • Concept 17-4A Scientists use live laboratory animals, non-animal tests, case reports of poisonings, and epidemiological studies to estimate the toxicity of chemicals, but these methods have limitations. • Concept 17-4B Many health scientists call for much greater emphasis on pollution prevention to reduce our exposure to potentially harmful candidates.

49. Many Factors Determine the Harmful Health Effects of a Chemical (1) • Toxicology • Toxicity dependent on • Dose • Age • Genetic makeup • Multiple chemical sensitivity (MCS) • Solubility and persistence of the chemical • Biomagnification • Response • Acute effect • Chronic effect

50. Science: Estimating Human Exposure to Chemicals and Measuring Their Effects