Environmental Hazards and Human Health

1. Environmental Hazards and Human Health Chapter 17

2. 17.1

3. Risks Are Usually Expressed as Probabilities • Risk – probability of suffering harm from a hazard that can cause injury, disease, death, economic loss, or damage • Gives likelihood of such an event

4. Possible…or Probably? • Possibility: it may happen • Example: It is possible that a smoker can get lung cancer. • Probability: estimate for the likelihood of an event • Example: The lifetime probability of developing lung cancer from smoking one pack of cigarettes per day is 1 in 250.

5. Risks Are Usually Expressed as Probabilities • Risk Assessment –using statistical methods to estimate how much harm a particular hazard can cause to human health or the environment • Risk Management – deciding whether or how to reduce a particular risk to a certain level and at what cost.

6. Science: Risk Assessment and Risk Management

7. Sensational News • Most people are not good at understanding and comparing risk… • American’s worry about getting avian flu • By mid-2008 had killed no one • Most American’s don’t get vaccinated for the common flu • Contributes to the deaths of 36,000 Americans each year

8. We Face Many Types of Hazards • Foods high in cholesterol or fat content • Lying out in the sun or going to a tanning salon • Living in a hurricane-prone area • How serious are the risks we face, and do the benefits of certain activities outweigh the risks?

9. Five major types of hazards • Biological: pathogens (bacteria, viruses, parasites, protozoa, and fungi) • Chemical: harmful chemicals in air, water, soil, and food • Physical: fire, earthquakes, volcanic eruptions, floods, and storms • Cultural: unsafe working conditions, unsafe highways, criminal assault, and poverty • Lifestyle choices: smoking, eating too much, drinking too much alcohol, and having unsafe sex

10. Your Turn! • Lifestyle Choices Game

11. Lifestyle Choices Game • Rules: • Water in cup represents your BODILY FLUIDS! • You are at a party where you are allowed to exchange bodily fluids… • Exchange: Pour all liquid in one cup into another, then pour half back in first cup • Only exchange fluids a total of three times • Do NOT exchange fluids with the same person more than once

12. Lifestyle Choices Game • OH NO…! • One person in the room is infected with influenza and does not know it… • Flu test: indicator will turn the liquid in their cup bright pink if they have the virus in their fluids

13. Lifestyle Choices Game • Round 2 –You determine the rules…peer pressure?

14. 17.2

15. Some Diseases Can Spread from One Person to Another • Nontransmissible disease – doesn’t spread from person to person • Ex. Cardiovascular disease • Risk increases with age… • Infectious disease – caused by pathogen that invades the body • Ex. Flu, HIV, TB • Transmissible disease (contagious or communicable disease) – infectious disease that spreads from person to person

16. Global Outlook: Worldwide, AIDS Is the Leading Cause of Death for Ages 15–49

17. Major Causes of Death in the World and in the United States in 2005

18. Leading cause of death is cardiovascular disease… • Since 1950, death from infectious diseases have declined due to • Better health care • Antibiotics • Vaccines • Disability-adjusted life years (DALYs) – measure of total disease burden in a population • Assesses amount of ill health (includes premature death and disability) • Controversial because difficult to evaluate the severity of various disabilities

19. Infectious Diseases Are Still Major Health Threats • Infectious diseases spread through • Air • Water • Food • Body fluids • Epidemics – large scale outbreak in a country • Pandemics – global epidemic

20. Science: Pathways for Infectious Diseases in Humans

21. The World’s Seven Deadliest Infectious Diseases Kill 12.5 Million People

22. Some Viral Diseases Kill Large Numbers of People • Influenza or flu virus • #1 Killer • Transmission • HIV • #2 Killer • Antiviral drugs • HBV • #3 Killer • Similar Transmission as HIV

23. 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)

24. Video Clip • Alien Invaders

25. 17.3 and 17.4

26. Energy Pyramid Review • Which level has the most energy? • Which level has the most organisms? • Which level has the least organisms? • Which level has the least energy?

27. Solution? • dichloro-diphenyl-trichloroethane • DDT

28. DDT • DDT was invented in the 1940’s and viewed as: • Miracle for farmers • Safe

29. DDT • Arial crop sprayers were used to spray tons of DDT on crops across the U.S

30. DDT Victim? • Scientists discovered that DDT was concentrated in the bald eagle • How? • DDT affected the eagle’s ability to reproduce

31. Biomagnification • The increase in concentration of an element or compound, such as the pesticide DDT, that occurs in a food chain

32. Some Chemicals Can Cause Cancers, Mutations, and Birth Defects • Toxic chemicals – cause temporary or permanent harm or death to humans and animals • Carcinogens – substances that promote cancer • Mutagens – substances that cause mutations in DNA (genetic  inheritable) • Teratogens – chemicals that cause harm or birth defects to a fetus or embryo

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

34. Some Chemicals May Affect Our Immune, Nervous, and Endocrine Systems • Hormonally active agents (HAAs) • Gender benders – effects on sexual development and reproduction • Thyroid disrupters – cause growth, weight, brain, and behavioral disorders • Phthlates (“thall-eights”) – chemicals used to soften PVC plastic used in toys, blood storage bags, and medical tubes • Birth defects, liver damage, premature breast development, immune suppression, etc.

35. Many Factors Determine the Harmful Health Effects of a Chemical • Toxicology – study of the harmful effects of chemicals on humans and other organisms • Toxicity dependent on • Dose – amount of a harmful chemical that a person has ingested, inhaled, or absorbed through the skin • Age • Genetic makeup • Multiple chemical sensitivity (MCS) • Solubility and persistence of the chemical • Biomagnification

36. Many Factors Determine the Harmful Health Effects of a Chemical • Response • Acute effect – immediate or rapid harmful reaction to an exposure • Chronic effect – permanent or long-lasting consequence

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

38. Case Study: Protecting Children from Toxic Chemicals • Analysis of umbilical cord blood: significance • 287 chemicals detected (180 carcinogenic, 217 neurological damage) • Children face a risk 10 times higher than that faced by adults…why?

39. Case Study: Protecting Children from Toxic Chemicals • Infants and children more susceptible to the toxic effects of chemicals than adults • Eat, drink, and breathe more per unit of body weight than adults • Put their fingers in their mouths • Less well-developed immune systems and body detoxification processes

40. Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity • Dose-response curve: median lethal dose (LD50) - Dose that can kill 50% of the animals in a test population within an 18 day period

41. Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity • Nonthreshold dose-response model – any dose causes damage • Threshold dose-response model – a threshold dosage must be reached before any detectable harm

42. Toxicity Ratings and Average Lethal Doses for Humans

43. Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity • Animal Testing: Can the data be extrapolated to humans?

44. Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity • More humane methods using animals • Replace animals with other models • Computer simulations • Tissue culture and individual animal cells • What are the effects of mixtures of potentially toxic chemicals?

45. There Are Other Ways to Estimate the Harmful Effects of Chemicals • Case reports and epidemiological studies • Limitations of epidemiological studies • Too few people tested • Length of time • Can you link the result with the chemical? • Can not be used for new hazards

46. Food for thought… • “Toxicologists know a great deal about a few chemicals, a little about many, and next to nothing about most.” • ~Joseph V. Rodricks (risk assessment expert) • 10% of 100,000 registered synthetic chemicals in commercial use have been screened for toxicity

47. Your Turn! • LD50 Toxicity Analysis

48. 17.5

49. 17-5 How Do We Perceive Risks and How Can We Avoid the Worst of Them? • Concept 17-5 We can reduce the major risks we face if we become informed, think critically about risks, and make careful choices.

50. Pollution Prevention and the Precautionary Principle • Those introducing a new chemical or new technology would have to follow new strategies • A new product is considered harmful until it can be proved to be safe • Existing chemicals and technologies that appear to cause significant harm must be removed