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17THMILLER/SPOOLMAN
LIVING IN THE ENVIRONMENT
Chapter 17Environmental 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• Lower sperm counts• Presence of both male and female sex organs
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
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
Baby Drinking from BPA Bottle
Fig. 17-1, p. 436
Risks Are Usually Expressed as Probabilities• Risk • Probability of suffering harm from a hazard• Probability vs. possibility
• Risk Assessment
• Risk Management
Science: Risk Assessment and Risk Management
Fig. 17-2, p. 437
We Face Many Types of Hazards
1. Biological:• Pathogen: an organism that causes disease in other
organisms
2. Chemical
3. Physical
4. Cultural
5. Lifestyle choices
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
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
Infectious Diseases Are Still Major Health Threats
• Infectious diseases spread through• Air• Water• Food• Body fluids
• Epidemics and pandemics
• Resistance of bacteria and insects to drugs and pesticides
Science: Pathways for Infectious Diseases in Humans
Fig. 17-3, p. 439
Major Causes of Death from Infectious Diseases in the World, 2007
Fig. 17-4, p. 439
Science Focus: Genetic Resistance to Antibiotics Is Increasing (1)
• Bacteria: rapid reproduction, easily spread
• Overuse of antibiotics
• Overuse of pesticides
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
Viral Diseases and Parasites Kill Large Numbers of People (2)
• Viruses that move form animals to humans• West Nile virus• Swine flu (H1N1)• Bird flu
• Reduce chances of infection: 1.Wash your hands2.Avoid touching your face3.Avoid sick people
Case Study: Malaria — The Spread of a Deadly Parasite (1)
• Malaria• Caused by Plasmodium sp. carried by Anopheles
mosquitoes • Tropical and subtropical regions• Malarial cycle
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
Global Outlook: Distribution of Malaria
Fig. 17-6, p. 444
A Boy in Brazil’s Amazon Sleeps Under an Insecticide-Treated Mosquito Net
Fig. 17-7, p. 445
Solutions: Infectious Diseases
Fig. 17-8, p. 445
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
Potential Pathways on Which Toxic Chemicals Move Through the Environment
Fig. 17-9, p. 447
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
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?1. Inhalation: vaporized Hg or particulates2. Eating fish with high levels of methylmercury3. Eating high-fructose corn syrup
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
Solutions: Mercury Pollution
Fig. 17-10, p. 449
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-increase plastic flexibility
Hormones and Hormones Mimics or Blockers
Fig. 17-11, p. 449
Many Factors Determine the Harmful Health Effects of a Chemical (1)
• Toxicology
• Toxicity dependent on• Dose • Age• Genetic makeup • Solubility • Persistence • Biomagnification
Many Factors Determine the Harmful Health Effects of a Chemical (2)
• Response• Acute effect: immediate or rapid• Chronic effect: permanent or long-lasting
Science: Estimating Human Exposure to Chemicals and Measuring Their Effects
Fig. 17-12, p. 452
Case Study: Protecting Children from Toxic Chemicals
• 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
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
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?
Toxicity Ratings and Average Lethal Doses for Humans
Table 17-1, p. 453
Are Trace Levels of Toxic Chemicals Harmful?
• Insufficient data for most chemicals
• We are all exposed to toxic chemicals
• Are the dangers increasing or are the tests just more sensitive?
Why Do We Know So Little about the Harmful Effects of Chemicals?
• Severe limitations estimating toxicity levels and risks
• Only 2% of 100,000 chemicals have been adequately tested
• 99.5% of chemicals used in the United States are not supervised by government
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
The Greatest Health Risks Come from Poverty, Gender, and Lifestyle Choices• Risk analysis • Risk assessment• Risk management• Risk communication
• Greatest health risks• Poverty• Gender• Lifestyle choices
Global Outlook: Number of Deaths per Year in the World from Various Causes
Fig. 17-16, p. 458Numbers in parentheses represent death tolls in terms of the number of fully loaded 200-passenger jet airplanes crashing every day of the year with no survivors.
Comparison of Risks People Face in Terms of Shorter Average Life Span
Fig. 17-17, p. 459
Most People Do a Poor Job of Evaluating Risks
1. Fear
2. Degree of control
3. Whether a risk is catastrophic or chronic
4. Optimism bias
5. Want instant gratification without thinking of future harm
Several Principles Can Help Us to Evaluate and Reduce Risk
1. Compare risks
2. Determine how much you are willing to accept
3. Determine the actual risk involved
4. Concentrate on evaluating and carefully making important lifestyle choices
Three Big Ideas
1. We face significant hazards from infectious diseases, malaria, and tuberculosis, and from exposure to chemicals that can cause cancers and birth defects, and disrupt the human immune, nervous, and endocrine systems.
2. Because of the difficulty in evaluating the harm caused by exposure to chemicals, many health scientists call for much greater emphasis on pollution prevention.
3. Becoming informed, thinking critically about risks, and making careful choices can reduce the major risks we face.