17THMILLER/SPOOLMAN

LIVING IN THE ENVIRONMENT

Chapter 17Environmental Hazards and Human Health

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.

Human Chemical Exposure

• We are exposed to numerous chemicals every day:• environmental sources such as air and water pollution• pesticides• cleaning products• food additives

• Some of these chemicals are threats to human health, but tracing exposures and determining what levels of risk they pose is a painstaking process. • How do harmful substances enter the body, and how do they damage

cells?• In this chapter, we learn how dangers are assessed, what kind of

regulations we use to reduce exposures, and how we manage associated human health risks.

Science: Risk Assessment and Risk Management

Fig. 17-2, p. 437

Risk assessment and risk management are used to estimate the seriousness of various risks and how to reduce such risks. Question: What is an example of how you have applied this process today?

We Face Many Types of Hazards

1. Biological:Pathogens are organisms that causes disease in other organisms.

2. Chemical

3. Physical

4. Cultural

5. Lifestyle choices

Write down two examples of each.

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.

Some Diseases Can Spread from One Person to Another, Others Cannot

• Infectious disease• Pathogen invades the body and multiplies

• Transmissible disease • Contagious or communicable disease• Infectious disease transmitted between people• Flu, tuberculosis, measles

• Nontransmissible disease• Not caused by living organisms• Heart disease, most cancers, diabetes

Which of theseare communicable?HIVMalariaAsthmaEbolaFlu

• Since 1950, death from infectious diseases have declined due to:• Better health care• Better sanitation• Antibiotics• Vaccines

Vast Improvements…

However … Infectious Diseases AreStill 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 (CDC, 2005)

From the Centers for Disease Control and Prevention (CDC) (Current)

What are the major causes of death from infectious diseases in the world?

Major Causes of Death from Infectious Diseases in the World, 2007

Fig. 17-4, p. 439

Current Event and W.H.O. Information Blitz

• Homework (About 2 nights worth):• Readings for Harkness on Thursday, Ebola.• Active reading establishes your base score.• Prompt for discussion already written.

• Read Core Case Study, p. 436; Science Focus, p. 442• Review Questions 2 and 3, p. 463• Reading as appropriate

Flu

Asthma

Case Study: Malaria — The Spread of a Deadly Parasite (1)

• Malaria• Caused by Plasmodium sp. carried by Anopheles

mosquitoes • Tropical and subtropical regions• Africa• Central and South America• Southeast Asia

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

• DDT effective against mosquitoes but banned in U.S.• DDT (dichlorodiphenyltrichloroethane) is a colorless,

crystalline, tasteless and almost odorless organochloride known for its insecticidal properties.

Global Outlook: Distribution of Malaria

Fig. 17-6, p. 444

Ebola

Science Focus: Genetic Resistance to Antibiotics Is Increasing (1)

• Bacteria: rapid reproduction, easily spread• Overuse of antibiotics• Overuse of pesticides

• Widespread use of pesticides or antibiotics eliminates the weaker individuals in a rapidly reproducing population.

• This causes an increase in the frequency of individuals in the population who have genetic resistance to pesticides or antibiotics because they are the ones left to rapidly reproduce.

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

Lung Tissue Destroyed by Tuberculosis

Fig. 17-5, p. 440

Science Focus (p. 442) Ecological Medicine: How Humans Get Infectious

Diseases from Animals

• Human practices that encourage the spread of diseases from animals to humans

• Emerging infections• HIV• Ebola virus• Avian flu• Hepatitis B• Lyme virus

A Boy in Brazil’s Amazon Sleeps Under an Insecticide-Treated Mosquito Net

Fig. 17-7, p. 445

This boy, who lives in Brazil’s Amazon Basin, is sleeping under an insecticide-treated mosquito netto reduce his risk of being bitten by malaria-carrying mosquitoes. Such nets cost about $5 each ancan be donated through groups such as www.MalariaNoMore.org.

We Can Reduce the Incidence ofInfectious Diseases

• Good news• Vaccinations on the rise• Oral rehydration therapy

• Bad news• More money needed for medical research in

developing countries

Solutions: Infectious Diseases

Fig. 17-8, p. 445

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.

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

Top 5 Toxic Substances—Human and Environmental Health

• Arsenic• Lead• Mercury• Vinyl chloride• Used to make PVC plastics

• Polychlorinated biphenyls• PCBs

Case Study: PCBs Are Everywhere—A Legacy from the Past

• Polychlorinated Biphenyl (PCB)--Class of chlorine-containing compounds• Very stable• Nonflammable• Break down slowly in the environment• Travel long distances in the air• Fat soluble

• Bioaccumulation• Biomagnification• Food chains and webs

• Banned, but found everywhere

Case Study: PCBs Are Everywhere—A Legacy from the Past

• PCBs belong to a broad family of man-made organic chemicals known as chlorinated hydrocarbons. PCBs were domestically manufactured from 1929 until their manufacture was banned in 1979.

• PCBs were used in hundreds of industrial and commercial applications including electrical, heat transfer, and hydraulic equipment; as plasticizers in paints, plastics, and rubber products; in pigments, dyes, and carbonless copy paper; and many other industrial applications.

PCBs

• Once in the environment, PCBs do not readily break down and therefore may remain for long periods of time cycling between air, water, and soil. PCBs can be carried long distances and have been found in snow and sea water in areas far away from where they were released into the environment. As a consequence, PCBs are found all over the world.

• PCBs can accumulate in the leaves and above-ground parts of plants and food crops. They are also taken up into the bodies of small organisms and fish. As a result, people who ingest fish may be exposed to PCBs that have bioaccumulated in the fish they are ingesting.

• PCBs have been demonstrated to cause cancer, as well as a variety of other adverse health effects on the immune system, reproductive system, nervous system, and endocrine system.

Potential Pathways on Which Toxic Chemicals Move Through the Environment

Fig. 17-9, p. 447

PCBs and other persistent toxic chemicals can move through th living and nonliving environment on a number of pathways.

Bioaccumulation and Biomagnification• Bioaccumulation: Organisms that consume toxic materials that do not break down

will eventually excrete or store these chemicals in their fatty tissues (fat soluble) over time; organisms can have a build up of toxins/chemicals.

• Biomagnification: The increased concentration of toxins in the tissues of organisms that are in higher levels of the food web/chain.

• Example: DDT (dichlorodiphenyltrichloroethane) is a colorless, crystalline, tasteless and almost odorless organochloride known for its insecticidal properties. • Found in tissues of different organisms within an aquatic ecosystem:• DDT in a water system- 0.00005 ppm• Water is consumed by algae, and the toxin is concentrated to 0.04 ppm.• Algae are consumed by primary consumers—shrimp—and the toxin is

concentrated to 0.16 ppm.• Shrimp are consumed by Secondary Consumers, eels, and the toxin is

concentrated to 0.28 ppm.• Eels are consumed by the Tertiary Consumers, the ring-billed gull, and the

toxin is concentrated to 75.5 ppm.

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• Hormones

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

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 methylmercury

Under certain conditions in aquatic environments, bacteria can convert inorganic mercury compounds to highly toxic methylmercury, which can be biomagnified in food chains/webs.

3. 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

Superfund Act

• Comprehensive Environmental Response, Compensation & Liability Act (CERCLA): Otherwise known as the Superfund Act- calls for a rapid cleanup of abandoned dumpsites containing toxic waste.

Video: Hazardous Chemicals inUrban Environments

• Habitable Planet

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.

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

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

• 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

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?

Hypothetical Dose-Response Curve Showing Determination of the LD50 (median lethal dose)

Fig. 17-13, p. 453* LD50 is the dose required to be lethal for 50% of the test population.

Toxicity Ratings and Average Lethal Doses for Humans

Table 17-1, p. 453

Science: Two Types of Dose-Response Curves

Fig. 17-14, p. 454

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?• Cannot be used for new hazards

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?

Some Potentially Harmful Chemicals Found in Most Homes

Fig. 17-15, p. 455

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 andthe 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

• 2000: global treaty to ban or phase out the dirty dozen persistent organic pollutants (POPs)

• 2007 REACH program in the European Union

Individuals Matter: Ray Turner and His Refrigerator

• 1974: Ozone layer being depleted by chlorofluorocarbons (CFCs)

• 1992: International agreement to phase out CFCs and other ozone-destroying chemicals

• Ray Turner: citrus-based solvents to clean circuit boards

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 by becoming informed, thinking critically about risks, and making careful choices.

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. 458

Comparison of Risks People Face in Terms of Shorter Average Life Span

Fig. 17-17, p. 459

Case Study: Death from Smoking (1)

• Most preventable major cause of suffering and premature death• Premature death of 5.4 million per year globally and

442,000 in the United States• Could be linked to increased dementia and

Alzheimer’s disease

• Nicotine: additive

• Effects of passive smoking (secondhand smoke)

Case Study: Death from Smoking (2)

• How to reduce smoking• Taxes• Classify and regulate nicotine• Bans on smoking in public places• Education

Normal Lung and Emphysema Lung

Fig. 17-18, p. 459

Annual Deaths in the U.S. from Tobacco Use and Other Causes

Fig. 17-19, p. 460

Most People Do a Poor Job ofEvaluating 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.

Three Big Ideas

3. Becoming informed, thinking critically about risks, and making careful choices can reduce the major risks we face.