CHAPTER 14
ENVIRONMENTAL HAZARDS AND HUMAN HEALTH
Outline
14-1 What major health hazards do we face?
A. Risks are usually expressed as probabilities.
1. A risk is the probability of suffering harm from a hazard that can cause injury, disease, death,
economic loss, or damage.
a. Probability—a mathematical statement about the likelihood that harm will be suffered from a
hazard.
i. “The lifetime probability of developing lung cancer from smoking one pack of cigarettes
per day is 1 in 250.” This means that 1 of every 250 people who smoke a pack of
c. Risk management involves deciding whether or how to reduce a particular risk to a certain
degree.
i. Comparative risk analysis.
B. We face many types of hazards.
1. Biological hazards from more than 1,400 pathogens that can infect humans.
a. A pathogen is an organism that can cause disease in another organism.
i. Bacteria.
2. Chemical hazards from harmful chemicals in air, water, soil, food, and human-made products.
3. Natural hazards such as fire, earthquakes, volcanic eruptions, floods, and storms.
5. Lifestyle choices such as smoking, making poor food choices, drinking too much alcohol, and
having unsafe sex.
14-2 What types of biological hazards do we face?
A. Some diseases can spread from one person to another.
1. An infectious disease is caused when a pathogen such as a bacterium, virus, or parasite invades the
2. Bacteria are singe-cell organisms that are found everywhere. Most are harmless or beneficial. A
bacterial disease results from an infection as the bacteria multiply and spread throughout the body.
3. Viruses are smaller than bacteria and work by invading a cell and taking over its genetic
4. A transmissible disease (also called a contagious or communicable disease) is an infectious
5. A nontransmissible disease is caused by something other than a living organism and does not
6. In 1900, infectious disease was the leading cause of death in the world.
7. Greatly reduced by a combination of better health care, the use of antibiotics to treat infectious
diseases caused by bacteria, and the development of vaccines.
B. Infectious diseases are still major health threats.
2. Spread through air, water, food, and body fluids such as feces, urine, blood, and droplets sprayed
by sneezing and coughing, and by pets, livestock, wild animals and insects.
4. A global epidemic such as tuberculosis or AIDS is called a pandemic.
5. Many disease-carrying bacteria have developed genetic immunity to widely used antibiotics and
6. CASE STUDY: The Growing Global Threat from Tuberculosis.
a. Since 1990, one of the world’s most underreported stories has been the rapid spread of
tuberculosis (TB). About 33% of the people on the planet are infected with the TB bacterium
and 10% of them will eventually become sick with active TB.
b. This highly infectious bacterial disease strikes about 9.3 million people per year and kills 1.3
million—about 84% of them in developing countries.
c. Several factors account for the recent spread of TB.
d. Efforts to develop more effective antibiotics and vaccines are being undertaken by
governments and private groups.
e. Researchers are developing new and easier ways to detect TB in its victims.
i. INDIVIDUALS MATTER: Three College Students Have Saved Thousands of Lives. In
7. SCIENCE FOCUS: Genetic Resistance to Antibiotics Is Increasing
a. Antibiotics are chemicals that can kill bacteria. Due to a high reproductive rate, bacteria can
become genetically resistant to antibiotics through natural selection.
b. Other factors that can promote genetic resistance are:
i. The spread of bacteria around the globe by human travel and international trade.
ii. The overuse of pesticides, which increases populations of pesticide-resistant carriers of
bacterial diseases.
vii. The growing use of antibacterial hand soaps and other antibacterial cleansers.
c. Every major disease-causing bacterium has now developed strains that resist at least one
antibiotic.
d. MRSA (methicillin-resistant staphylococcus aureus) is resistant to most antibiotics and can
Chapter 14: Environmental Hazards and Human Health
C. Viral diseases and parasites kill large numbers of people.
1. Viruses evolve quickly, are not affected by antibiotics, and can kill large numbers of people.
a. The biggest killer is the influenza, or flu, virus, which is transmitted by the body fluids or
airborne emissions of an infected person.
1. Emergent diseases are illnesses that were previously unknown or were absent in human
2. Greatly reduce your chances of getting infectious diseases by practicing good, old-fashioned
hygiene.
3. CASE STUDY: The Global HIV/AIDS Epidemic.
a. The global spread of acquired immune deficiency syndrome (AIDS), caused by infection
with the human immunodeficiency virus (HIV), is a major global health threat.
i. In 2009, a total of about 33 million people worldwide (1.1 million in the
United States) are living with HIV.
b. Currently, there is no vaccine to prevent HIV infection and no cure for AIDS.
4. CASE STUDY: Malaria—Death by Parasite-Carrying Mosquitoes.
a. Almost half of the world’s people are at risk from malaria, as is anyone traveling to malaria-
prone areas, because there is no vaccine that can prevent this disease.
b. More than 80% of malaria’s victims live in sub-Saharan Africa.
c. Malaria is caused by a parasite that is spread by the bites of certain mosquito species.
d. Infects and destroys red blood cells, causing intense fever, chills, drenching sweats, anemia,
severe abdominal pain, headaches, vomiting, extreme weakness, and greater susceptibility to
other diseases.
j. CONNECTIONS: Deforestation and Malaria
a. Clearing and developing tropical forests has led to the local spread of malaria. A 5%
loss of tree cover in one part of Brazil’s Amazon forest led to a 50% increase in malaria
in that study area. Deforestation may create pools of water that make ideal breeding
ponds for malaria-carrying mosquitoes.
D. We can reduce the incidence of infectious diseases
1. The percentage of global death rate from infectious diseases decreased from 35% to 17%
between 1970 and 2006, and is projected to drop to 16% by 2015.
2. From 1971-2006, the percentage of children in developing countries who were immunized
3. An important breakthrough has been the development of simple oral rehydration therapy—
administering a simple solution of boiled water, salt, and sugar or rice.
4. CONNECTIONS: Drinking Water, Latrines, and Infectious Diseases.
a. More than a third of the world’s people do not have sanitary bathroom facilities, and
5. Philanthropists including Bill and Melinda Gates and Warren E. Buffet have donated billions
14-3 What types of chemical hazards do we face?
A. Some chemicals can cause cancers, mutations, and birth defects.
1. A toxic chemical is one that can cause temporary or permanent harm or death to humans and
animals.
2. In 2004, the U.S. Environmental Protection Agency listed arsenic, lead, mercury, vinyl chloride
3. There are three major types of potentially toxic agents.
a. Carcinogens are chemicals, types of radiation, or certain viruses that can cause or promote
cancer.
i. Examples are arsenic, benzene, formaldehyde, gamma radiation, PCBs, radon, certain
chemicals in tobacco smoke, ultraviolet (UV) radiation, and vinyl chloride.
b. Mutagens are chemicals or forms of radiation that cause mutations, or changes, in the DNA
molecules found in cells, or that increase the frequency of such changes.
i. Nitrous acid (HNO2), formed by the digestion of nitrite (NO2 –) preservatives in foods,
can cause mutations linked to increases in stomach cancer in people who consume large
B. Some chemicals may affect our immune and nervous systems.
1. Our body’s immune system protects us against disease and harmful substances by forming
antibodies that render invading agents harmless, but some chemicals interfere with this process.
2. Some natural and synthetic chemicals in the environment, called neurotoxins, can harm the human
nervous system, causing the following effects.
3. Examples of neurotoxins.
a. PCBs.
4. SCIENCE FOCUS: Mercury’s Toxic Effects.
a. High levels of mercury can damage the human nervous system, kidneys, and lungs. Low
levels of mercury can also harm fetuses and cause birth defects.
b. Natural sources account for about one-third of the mercury reaching the atmosphere.
c. Remaining two-thirds come from human activities.
i. Primarily from the smokestacks of coal-burning power plants and coal-burning industrial
facilities.
8. The EPA estimates that about one of every 12 women of childbearing age in the United States has
enough mercury in her blood to harm a developing fetus.
d. The greatest risk from exposure to low levels of methylmercury is brain damage in fetuses
and young children.
e. Methylmercury may also harm the heart, kidneys, and immune system of adults.
f. EPA advised nursing mothers, pregnant women, and women who may become pregnant not
C. Some chemicals affect the human endocrine system.
a. The endocrine system is a complex network of glands that release tiny amounts of hormones that
regulate human:
i. Reproduction.
ii. Growth.
b. Hormonally active agents (HAA) are synthetic chemicals that disrupt the endocrine system in
humans and some other animals.
i. Examples include aluminum, Atrazine™ and several other herbicides, DDT, PCBs,
mercury, phthalates, and bisphenol A (BPA).
ii. Some disrupt the endocrine system by attaching to estrogen receptor molecules.
iii. Thyroid disrupters cause growth, weight, brain, and behavioral disorders.
iv. BPA is found in plastic water bottles, baby bottles and the plastic resins line food
containers.
2. Studies funded by the chemical industry found no evidence or only weak evidence,
for adverse effects from low-level exposure to BPA in test animals.
4. In 2010, Canada classified BPA as a toxic chemical and banned its use in baby
bottles, and the European Union voted to ban the sale of plastic baby bottles that
1. Phthalates cause cancer and other health problems in laboratory animals.
14-4 How can we evaluate chemical hazards?
A. Many factors determine the harmful health effects of chemicals.
1. Toxicology is the study of the harmful effects of chemicals on humans and other organisms.
a. Toxicity is a measure of the harmfulness of a substance.
b. Any synthetic or natural chemical can be harmful if ingested in a large enough quantity.
c. The dose is the amount of a harmful chemical that a person has ingested, inhaled, or absorbed
through the skin.
d. Many variables can affect the level of harm caused by a chemical.
i. Toxic chemicals usually have a greater effect on fetuses, infants, and children than on
adults.
2. The damage to health resulting from exposure to a chemical is called the response.
a. Acute effect is an immediate or rapid harmful reaction ranging from dizziness and nausea to
3. CASE STUDY: Protecting Children from Toxic Chemicals.
a. In 2005, the Environmental Working Group analyzed umbilical cord blood from 10 randomly
selected newborns in U.S. hospitals.
i. 287 chemicals detected, 180 cause cancers in humans or animals, 217 damage the brain
B. Scientists use live laboratory animals and non-animal tests to estimate toxicity.
1. The most widely used method for determining toxicity is to expose a population of live laboratory
animals to measured doses of a specific substance under controlled conditions.
2. Laboratory-bred mice and rats are widely used because, as mammals, their systems function
somewhat like human systems.
a. Results plotted in a dose-response curve.
b. Determine the lethal dose—the dose that will kill an animal.
Chapter 14: Environmental Hazards and Human Health
C. There are other ways to estimate the harmful effects of chemicals.
1. Case reports, usually made by physicians, provide information about people suffering some
adverse health effect or death after exposure to a chemical.
2. Epidemiological studies, which compare the health of people exposed to a particular chemical (the
experimental group) with the health of a similar group of people not exposed to the agent (the
control group), but limited by:
a. Too few people have been exposed to high enough levels of a toxic agent to detect statistically
been exposed.
D. Are trace levels of toxic chemicals harmful?
1. Almost everyone is now exposed to potentially harmful chemicals that have built up to trace
levels in their blood and in other parts of their bodies.
2. In most cases, we do not know if we should be concerned about trace amounts of various synthetic
3. Possible potential long-term effects on the human immune, nervous, and endocrine systems.
4. The risks from trace levels may be minor.
E. Why do we know so little about the harmful effects of chemicals?
1. All methods for estimating toxicity levels and risks have serious limitations.
2. Only 10% of the more than 80,000 registered synthetic chemicals in commercial use have been
3. Because of insufficient data and the high costs of regulation, federal and state governments do not
supervise the use of nearly 99.5% of the commercially available chemicals in the United States.
F. How far should we go in using pollution prevention and the precautionary principle?
1. Some are pushing for much greater emphasis on pollution prevention.
2. Do not release into the environment chemicals that we know or suspect can cause significant
3. The precautionary principle advocates when there is reasonable but incomplete scientific evidence
of significant or irreversible harm to humans or the environment from a proposed or existing
4. In 2000, a global treaty banned or phased out the use of 12 of the most notorious persistent organic
5. In 2007, the European Union enacted regulations known as REACH (for registration, evaluation,
and authorization of chemicals) that put more of the burden on industry to show that chemicals are
6. Individuals Matter: Ray Turner and His Refrigerator
a. In 1992, most of the world’s nations signed an agreement to phase out the use of
14-5 How do we perceive risks and how can we avoid the worst of them?
A. The greatest health risks come from poverty, gender, and lifestyle choices.
1. Risk analysis involves identifying hazards and evaluating their associated risks.
a. Risk assessment.
2. The greatest risk by far is poverty.
3. The second greatest risk is gender.
4. The best ways to reduce one’s risk of premature death and serious health problems are to:
a. avoid smoking and exposure to smoke
b. lose excess weight
5. CASE STUDY: Death from Smoking.
a. Cigarette smoking kills an average of about 14,800 people every day.
b. Cigarette smoking is the world’s most preventable major cause of suffering and premature
death among adults.
c. Tobacco contributes to the premature deaths of at least 5.4 million people annually from 25
illnesses, including:
i. Heart disease.
d. In 2009, the CDC estimated that smoking kills about 443,000 Americans per year prematurely.
e. Nicotine inhaled in tobacco smoke is highly addictive.
f. Passive smoking, or breathing secondhand smoke, poses health hazards.
B. Estimating risks from technologies is not easy.
1. The more complex a technological system, and the more people needed to design and run it, the
more difficult it is to estimate the risks of using the system.
2. The overall reliability or the probability (expressed as a percentage) that a person, device, or
complex technological system will complete a task without failing is the product of:
1. Many people deny or shrug off the high-risk chances of death (or injury) from voluntary activities
they enjoy, such as:
2. Some of these same people may be terrified about their chances of being killed by:
a. A gun (1 in 28,000 in the United States).
b. Flu (1 in 130,000).
3. Five factors can cause people to be being more or less risky than experts judge.
a. Fear.
D. Several principles can help us evaluate and reduce risk.
2. Determine how much risk you are willing to accept.
4. Concentrate on evaluating and carefully making important lifestyle choices.
E. Three big ideas for this chapter:
1. We face significant hazards from infectious diseases such as flu, AIDS, diarrheal diseases,
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.
Objectives
14-1 What major health hazards do we face?
CONCEPT 14-1 We face health hazards from biological, chemical, physical, and cultural factors, and from the
lifestyle choices we make.
1. Define risk, risk assessment, and risk management. List the five classes of common hazards and give
two examples of each.
14-2 What types of biological hazards do we face?
CONCEPT 14-2 The most serious biological hazards we face are infectious diseases such as flu, AIDS,
tuberculosis, diarrheal diseases, and malaria.
1. Define pathogen, bacteria and viruses. Distinguish among infectious, transmissible and
nontransmissible diseases. List ways that infectious diseases are spread. Define epidemic and
14-3 What types of chemical hazards do we face?
CONCEPT 14-3 There is growing concern about chemicals in the environment that can cause cancers and birth
defects, and disrupt the human immune, nervous, and endocrine systems.
1. Define toxic chemical, carcinogen, mutagen and teratogen and give two examples of each. Distinguish
between chemicals that can cause cancers and birth defects and those that disrupt the human immune,
nervous, and endocrine systems. What effects do BPA and mercury have? List several products that
14-4 How can we evaluate chemical hazards?
CONCEPT 14-4A Scientists use live laboratory animals, case reports of poisonings, and epidemiological
studies to estimate the toxicity of chemicals, but these methods have limitations.
CONCEPT 14-4B Many health scientists call for much greater emphasis on pollution prevention to reduce our
exposure to potentially harmful chemicals.
1. Define toxicology, toxicity and dose. Distinguish between acute and chronic effect. List several factors
2. Establish the relationship between pollution prevention and the precautionary principle.
14-5 How do we perceive risks and how can we avoid the worst of them?
CONCEPT 14-5 We can reduce the major risks we face by becoming informed, thinking critically about risks,
and making careful choices.
1. Define risk analysis. List the top three risks. List 5 ways to reduce one’s risk of premature death and
Key Terms
bacteria
carcinogens
dose
dose-response curve
pathogen
precautionary principle
response
risk
scientific principles of
sustainability
teratogens
toxic chemical
Teaching Tips
Many students on American college campuses are not as concerned about the AIDS epidemic as one might
hope. The instructor can introduce this chapter by asking students whether they thought WWII was the
worst human disaster in recent memory.
• Follow that up by asking them whether they know what the death toll was—40 million deaths.
• Ask them if they think this might be on the same level as the AIDS epidemic.
Diseases can travel very quickly. Go to a website that tracks the flu, and look at how quickly it spreads.
Chapter 14: Environmental Hazards and Human Health
• Prepare a coin with a yeast solution. Then, ask your students to pass it around then swab their
Discussion Topics
1. What are several environmental risks? How can these risks be minimized?
2. What lifestyle risks do people take and how dangerous are these practices?
3. What are several transmissible disease risks and their history of infection and prevention?
Activities and Projects
1. Have local public health officials discuss with your class the types and frequency of diseases in the
local area, and describe efforts for disease control.
2. Invite a spokesperson for the American Cancer Society to address your class on the subject of
“nonsmokers’ rights.” What specific things can a person do to minimize his or her passive exposure to
4. Assign several students to visit a store that specializes in organically grown and “natural” foods. Have
them describe the advertising claims made on behalf of natural foods.
5. Have your students obtain mortality and morbidity data for people living in poor and affluent sections
6. What occupational health hazards are prevalent in your community? What is being done to protect
workers from these on-the-job hazards? Have some students investigate this subject and report the
results to the class.
Attitude and Values Assessment
1. What kinds of risks do you take every day? Do you consider these to be significant risks?
2. What kinds of risks from the natural environment occur in your area?
3. What kinds of risks are you exposed to each day over which you have no control?
4. Do you feel that societal risks should be distributed equally among all citizens?
Laboratory Skills
Wells, Edward. Lab Manual for Environmental Science. 2009. Lab #4: Biomagnification Through a Food
Chain.
Wells, Edward. Lab Manual for Environmental Science. 2009. Lab #16: Human Health Risk Assessment.
News Videos
Who Pays the Price for Technology?, The Brooks/Cole Environmental Science Video Library 2009,
©2011, DVD ISBN-13: 978-0-538-73355-7
Additional Video Resources
We all Live Downstream (Documentary, 1991)
A look at pollution in the Mississippi River and the effects on human health.