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.