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Chapter 17 Environmental Hazards and Human Health

Chapter 17 Environmental Hazards and Human Health. Core Case Study: Are Baby Bottles and Food Cans Safe To Use? The BPA Controversy (1). Some synthetic chemicals act as hormone mimics and disrupt the human endocrine system Excess estrogen effects on males Feminization Smaller penis

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Chapter 17 Environmental Hazards and Human Health

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  1. Chapter 17 Environmental Hazards and Human Health

  2. Core Case Study: Are Baby Bottles and Food Cans Safe To Use? The BPA Controversy (1) • Some synthetic chemicals act as hormone mimics and disrupt the human endocrine system • Excess estrogen effects on males • Feminization • Smaller penis • Lower sperm counts • Presence of both male and female sex organs

  3. Core Case Study: Are Baby Bottles and Food Cans Safe To Use? The BPA Controversy (2) • BPA (bisphenol A) • Estrogen mimic • In polycarbonates and other hardened plastics • Baby bottles and sipping cups • Reusable water bottles • Sports drink and juice bottles • Microwave dishes • Food storage containers • Liners of most food and soft drink cans

  4. Core Case Study: Are Baby Bottles and Food Cans Safe To Use? The BPA Controversy (3) • BPA leaches into foods and drinks • Even when containers not heated • 93% of Americans older than 6 have BPA levels above the threshold level set by the EPA • Higher in children and adolescents • Risks for infants, children, adults

  5. Baby Drinking from BPA Bottle Fig. 17-1, p. 436

  6. 17-1 What Major Health Hazards Do We Face? • Concept 17-1 We face health hazards from biological, chemical, physical, and cultural factors, and from the lifestyle choices they make.

  7. Risks Are Usually Expressed as Probabilities • Risk • Probability of suffering harm from a hazard • Probability vs. possibility • Risk Assessment • Risk Management

  8. Science: Risk Assessment and Risk Management Fig. 17-2, p. 437

  9. We Face Many Types of Hazards • Biological: • Pathogen: an organism that causes disease in other organisms • Chemical • Physical • Cultural • Lifestyle choices

  10. 17-2 What Types of Biological Hazards Do We Face? • Concept 17-2 The most serious biological hazards we fade are infectious diseases such as flu, AIDS, tuberculosis, diarrheal diseases, and malaria.

  11. Some Diseases Can Spread from One Person to Another (1) • Infectious disease • Pathogen invades the body and multiplies • Transmissible disease • Contagious or communicable disease • Infectious disease transmitted between people • Flu, tuberculosis, measles

  12. Some Diseases Can Spread from One Person to Another (2) • Nontransmissible disease • Not caused by living organisms • Heart disease, most cancers, diabetes • Since 1950, death from infectious diseases have declined due to • Better health care • Better sanitation • Antibiotics • Vaccines

  13. Infectious Diseases Are Still Major Health Threats • Infectious diseases spread through • Air • Water • Food • Body fluids • Epidemics and pandemics • Resistance of bacteria and insectsto drugs and pesticides

  14. Science: Pathways for Infectious Diseases in Humans Fig. 17-3, p. 439

  15. Major Causes of Death from Infectious Diseases in the World, 2007 Fig. 17-4, p. 439

  16. Science Focus: Genetic Resistance to Antibiotics Is Increasing (1) • Bacteria: rapid reproduction, easily spread • Overuse of antibiotics • Overuse of pesticides

  17. Science Focus: Genetic Resistance to Antibiotics Is Increasing (2) • Methicillin-resistant Staphylococcus aureus (MRSA) • Resistant to most antibiotics • Symptoms of MRSA • How will it be controlled?

  18. Case Study: The Growing Global Threat from Tuberculosis • One in ten will become sick with TB • 1.8 million deaths each year, primarily in less-developed countries • 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

  19. Lung Tissue Destroyed by Tuberculosis Fig. 17-5, p. 440

  20. Individuals Matter: Three College Students Have Saved Thousands of Lives • North Carolina State seniors • Developed a device that can detect TB bacteria on a slide • Very useful in less-developed countries

  21. Viral Diseases and Parasites Kill Large Numbers of People (1) • Influenza or flu virus • #1 Killer • HIV • #2 Killer • Hepatitis B virus (HBV) • #3 Killer • Emergent diseases:West Nile virus

  22. Viral Diseases and Parasites Kill Large Numbers of People (2) • Viruses that move form animals to humans • West Nile virus • Ecological medicine • Reduce chances of infection: • Wash your hands • Avoid touching your face • Avoid sick people

  23. Science Focus: Ecological Medicine: How Humans Get Infectious Diseases from Animals • Ecological medicine • Human practices that encourage the spread of diseases from animals to humans • Emerging infections • HIV • Avian flu • Hepatitis B • Lyme virus

  24. Case Study: Global HIV/AIDS Epidemic (1) • 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

  25. Case Study: Global HIV/AIDS Epidemic (2) • 25 million deaths, so far • #1 killer globally of women 15-49 • Most prevalent in sub-Saharan Africa • Life expectancy dropped from 62 to 47 • Alters age structure of population

  26. Case Study: Malaria — The Spread of a Deadly Parasite (1) • Malaria • Caused by Plasmodium sp. carried by Anopheles mosquitoes • Tropical and subtropical regions • Spread • Symptoms • Malarial cycle

  27. Case Study: Malaria — The Spread of a Deadly Parasite (2) • Malaria on the rise since 1970 • Drug resistant Plasmodium • Insecticide resistant mosquitoes • Clearing of tropical forests • AIDS patients particularly vulnerable • Prevention of spread and current research

  28. Global Outlook: Distribution of Malaria Fig. 17-6, p. 444

  29. A Boy in Brazil’s Amazon Sleeps Under an Insecticide-Treated Mosquito Net Fig. 17-7, p. 445

  30. 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

  31. Solutions: Infectious Diseases Fig. 17-8, p. 445

  32. 17-3 What Types of Chemical Hazards Do We Face? • Concept 17-3 There is growing concern about chemicals in the environment that can cause cancers and birth defects, and disrupt the human immune, nervous, and endocrine system.

  33. Some Chemicals Can Cause Cancers, Mutations, and Birth Defects • Toxic chemicals • Carcinogens • Chemicals, types of radiation, or certain viruses the cause or promote cancer • Mutagens • Chemicals or radiation that cause mutations or increase their frequency • Teratogens • Chemicals that cause harm or birth defects to a fetus or embryo

  34. 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

  35. Potential Pathways on Which Toxic Chemicals Move Through the Environment Fig. 17-9, p. 447

  36. Some Chemicals May Affect Our Immune and Nervous Systems • Some natural and synthetic chemicals in the environment can weaken and harm • Immune system • Nervous system • Neurotoxins: PCBs, arsenic, lead, some pesticides • Endocrine system

  37. 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 • How are humans exposed? • Inhalation: vaporized Hg or particulates • Eating fish with high levels of methylmercury • Eating high-fructose corn syrup

  38. Science Focus: Mercury’s Toxic Effects (2) • Effects of Hg on humans • Damage nervous system, kidneys, lungs • Harm fetuses and cause birth defects • Who is most at risk? • Pregnant women • 75% of exposure comes from eating fish

  39. Solutions: Mercury Pollution Fig. 17-10, p. 449

  40. Some Chemicals Affect the Human Endocrine System • Glands that release hormones that regulate bodily systems and control sexual reproduction, growth, development, learning, behavior • Hormonally active agents have similar shapes and bind to hormone receptors • Gender benders • Thyroid disruptors • BPA? • Phthalates in plastics

  41. Hormones and Hormones Mimics or Blockers Fig. 17-11, p. 449

  42. 17-4 How Can We Evaluate and Deal with Chemical Hazards? • Concept 17-4A Scientists use live laboratory animals, 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 chemicals.

  43. Many Factors Determine the Harmful Health Effects of a Chemical (1) • Toxicology • Toxicity dependent on • Dose • Age • Genetic makeup • Multiple chemical sensitivity (MCS) • Solubility • Persistence • Biomagnification

  44. Many Factors Determine the Harmful Health Effects of a Chemical (2) • Response • Acute effect: immediate or rapid • Chronic effect: permanent or long-lasting

  45. Science: Estimating Human Exposure to Chemicals and Measuring Their Effects Fig. 17-12, p. 452

  46. Case Study: Protecting Children from Toxic Chemicals • Analysis of umbilical cord blood: significance • Infants and children more susceptible • Eat, drink water, 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 • Fetal exposure may increase risk of autism, asthma, learning disorders

  47. Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity (1) • Mice and rats • Systems are similar to humans • Small, and reproduce rapidly • Is extrapolation to humans valid? • Dose-response curve: median lethal dose (LD50) • Nonthreshold dose-response model • Threshold dose-response model

  48. Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity (2) • More humane methods using animals • Replace animals with other models • Computer simulations • Tissue culture and individual animal cells • Chicken egg membranes • What are the effects of mixtures of potentially toxic chemicals?

  49. Hypothetical Dose-Response Curve Showing Determination of the LD50 Fig. 17-13, p. 453

  50. Toxicity Ratings and Average Lethal Doses for Humans Table 17-1, p. 453

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