CHAP TER
11
Environmental Health
Source: Deglr6328. 2005. Adaptation of NASA. The blue marble. http://commons.wikimedia.org/wiki/File:The_Blue_Marble.jpg. 1972.
In many ways, environmental health is a fitting conclusion to this text. The subject has already come up repeatedly.
In truth, your health is not just a personal issue. Beginning in Chapter 1 you learned that lifestyle and environmental
factors have a much greater influence on your health and longevity than genetics. That theme recurred in all the
chapters on major diseases (infectious diseases, diabetes, cardiovascular disease, and cancer). You learned how your
social environment and the safety of your neighborhood influence health. Family planning, discussed in Chapter
10 has a profound effect on the environment—a concept we’ll expand upon in this chapter. Chapter 3 examined
the environmental impact of agriculture and individual food choices. In [Content Removed: #white_1.0-ch13] you
learned that your body forms an ecosystem, a complex system of interacting organisms and their physical
environment. In this chapter, you’ll learn how our behaviors impact broader ecosystems and how those ecosystems
affect our health.
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The global environment affects us all. The news media are full of ominous reports:
<
2014 Warmest Year in Modern Record[1]
<
World's Largest Ice Sheets Melting at Fastest Rate Ever Recorded[2]
<
Human-Caused Global Warming Contributed to Weather Extremes[3]
<
Researchers Link Syrian Conflict to a Drought Made Worse by Climate Change[4]
<
Coral Bleaching Threatening Reefs in Northern Pacific Due to Global Warming[5]
<
Climate Change Threatens Half of America's Bird Species [6]
This chapter will explore the influence of the local and global environment on human health. It will also address the
power of humans, collectively and individually, to affect the environment and the steps you can take now to
improve planetary health.
In nature nothing exists alone.
- Rachel Carson, scientist, environmentalist, and author of Silent Spring
1. HUMANS AND THE ENVIRONMENT
L E A R N I N G
1.
2.
3.
4.
5.
6.
environment
External surroundings,
including living and nonliving
things.
O B J E C T I V E S
Explain the reciprocal interaction between humans and the environment.
Define environmental health.
Discuss the relevance of population growth to environmental health.
Review common air and water pollutants and discuss ways to reduce your exposure.
Discuss the ways individuals can reduce solid waste.
Understand the impact of artificial lighting and excessive noise on health.
A reciprocal relationship exists between you and your environment—your external surroundings—both living and nonliving. Your actions can dramatically affect the health of the environment.
Likewise, the environment profoundly affects your health. We can’t live without oxygen, water, and soil
rich enough to grow plants and graze animals. The earth provides a host of resources that we use for
food, building materials, and the energy to light and heat our homes and power our machines.
The environment separates into two main components. The natural environment refers to areas
and ecosystems that existed before human influence. The ever-growing human population affects that
natural environment in many ways, from encroaching on wilderness areas and wildlife habitat to changing the chemistry of air and water. In contrast, the built environment refers to manmade structures
such as buildings, parks, transportation systems, and energy networks.
Another categorical division is the local and the global environment. You fit into a local ecosystem
that includes the built and natural environments. As you’ve learned in earlier chapters, a number of
local environmental factors affect your health and well-being: social relationships; neighborhood safety;
access to parks and recreation centers; and the quality of the food, water, soil, and air you breathe. You
can even examine the environment you inhabit on a smaller scale—your living space. You can control
some aspects of your personal environment, such as lighting, heating, sounds, smells, textures, and
sights. You create positive environmental changes by putting a potted plant on the windowsill, hanging
art on the walls, and playing peaceful music. Light a cigarette and you fill the air with toxic chemicals.
Our local environments contribute to the global environment, which affects us all. For example, air
pollutants from Europe and Asia create a perceivable haze over the Arctic.[7] Our actions affect not only
the health of people halfway across the globe but also the health of future generations.
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As a species, humans have had an enormous impact on the planet. For centuries, we have controlled and exploited the natural world in order to grow crops, build cities, extract natural resources,
manufacture goods, and live as safely and as comfortably as possible.
Yet Homo sapiens is one of many species occupying the earth. Our actions have altered multiple
ecosystems, often in ways that ultimately harm us. For instance, we have cut and burned entire forests
to create agricultural fields, pasture land, golf courses, and housing tracts.
Deforestation (loss of forest cover) has many adverse effects. Among their functions, forests
provide habitats for diverse species, filter the water (making it cleaner to drink), retain precipitation,
stabilize the ground to prevent erosion, stabilize snow to inhibit avalanches, provide building materials
and medicinal plants, offer shade and wind blocks, and take up atmospheric carbon dioxide. (Later,
we’ll discuss the role of carbon dioxide in global warming.) As one example of the impact on human
health, removal of trees creates the right mix of sunlight, warmth, and puddles for mosquito breeding.
In the Amazon, a 4 percent increase in deforestation led to a 50 percent rise in malaria.[8]
On a positive note, collective awareness about the relationship between our actions and human
and planetary health has steadily climbed.
Deforestation
The removal of a forest or
stand of trees.
1.1 The Evolution of Environmentalism
While healers have long recognized that our environments affect our health, it took some time for society to recognize that human activities often degrade the natural environment, which, in turn, damages
human health. The story begins with infectious microorganisms. Ancient physician Hippocrates broke
ranks with contemporaries by proposing that environmental factors—as opposed to angry
gods—caused illness. Much later, in the 1880s, scientists such as Robert Koch linked microbes to infectious illnesses.
Public health initiatives led to safe drinking water, sewage treatment, and the organized disposal of
garbage, including hazardous wastes. Such programs to curb infectious diseases marked the beginning
of environmental health, a discipline devoted to addressing the many external factors that can potentially affect health.[9] Initial efforts to prevent the spread of infectious disease expanded to the protection of air, water, and soil from physical, biological, and chemical pollutants and toxins.
The need to more broadly protect the environment arose with increasing migration from the
countryside to cities. Denser populations intensified the challenge of providing clean water and sanitation. Rivers passing through cities became rank with sewage run-off. Smoke from wood and coal fires
thickened the air with soot. Burning coal emitted sulfur dioxide and nitrogen oxides, both of which react with atmospheric water and other chemicals to form acid rain.[10] The acids fell to the ground as
fog, mist, rain, and snow. They became incorporated into dust or smoke, settling onto soil, buildings,
and plants and contributing to deforestation.
Efforts to regulate air pollution occurred as far back as 1306 in London.[11] Around 1760, the Industrial Revolution began in that city, increasing the release of pollutants into water and air. Smog, a
combination of fog and chemical-laden smoke, blanketed the city. In December 1952, poor air quality
led to 4,000 premature deaths, most of them due to respiratory and cardiovascular disease and most of
them affecting the elderly.[12]
Industrialization radically increased use of natural resources such as water (used as a source of
power), minerals (iron, asbestos, aluminum, stone, sand, lead, and mercury) and fossil fuels (coal, oil,
and natural gas). Fossil fuels are those formed millions of years ago as prehistoric plants and animals
became compressed under layers of earth. Because it takes so long to make them, fossil fuels are not renewable (easily replenished).
Furthermore, mining of minerals dramatically altered the landscape and introduced toxic industrial metals into the environment. Mercury, asbestos, and lead are prime examples. In 19th-century England, hats were made from felt (condensed wool), whose production involved mercury. Mercury damages the nervous system, including the brain—hence the expression “As mad as a hatter.”[13] Asbestos
fibers—used in insulation, drywall, concrete, bricks, and pipes—are easily inhaled, leading to lung cancer and other chronic chest diseases. Lead—used in metal alloys, bullets, batteries, ceramic glazes, cosmetics, and paint—damages many body systems, particularly the nervous system.
Industrialization did facilitate the growth of the middle class and a corresponding rise in living
standards. However, increased prosperity correlates with increased consumption of goods, most of
which use natural resources. Improvements in agriculture increased food production, which allowed
the population to swell and further taxed natural resources.
In the mid-1900s, the Green Revolution radically increased food production through the use of
mechanized farm equipment, improved crop varieties and irrigation techniques, pesticides (substances
that destroy organisms such as insects, undesirable plants, and fungi), and synthetic fertilizer. Unfortunately, pesticides and fertilizers added to the pollution problem. For example, the pesticide DDT
© 2013 Flat World Knowledge, Inc. All rights reserved.
environmental health
A discipline that addresses
the many external factors
that can potentially affect
health.
acid rain
The deposition of
atmospheric sulfur and nitric
acids as precipitation or in dry
form (smoke or dust).
Smog
Fog thickened and darkened
by air pollution.
fossil fuels
Energy resources derived
from ancient plants and
animals compressed in the
ground for millions of years.
They include oil (petroleum),
natural gas, and coal.
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304
FIGURE 11.1
London during the Great
Smog of 1952
Source: Stobbs NT. Nelson’s column
in December.
http://commons.wikimedia.org/wiki/
File:Nelson's_Column_during
_the_Great_Smog_of_1952.jpg. 1952.
HEALTH NOW VERSION 2.0.4
effectively controlled crop insects, as well as malaria and typhus. However, it also caused cancer and
killed marine organisms (crayfish, shrimp, fish).[14] Because it thinned eggshells, many bird species became unable to successfully reproduce.
In her 1962 book Silent Spring (which refers to a spring without birdsong), marine biologist Rachel
Carson made the connection between this environmental devastation and DDT, as well as other pesticides. Her work inspired the environmental movement. She moved beyond ecology (the study of the
relationship between organisms and their environment) and conservationism (the preservation of the
natural environment) to environmentalism. Environmentalism extended beyond valuing the natural
environment to regulating potential threats and disciplining polluters.
Environmental stewardship holds that humans have some obligation to preserve and protect natural settings. Motivations for doing so vary. Healthy ecosystems provide us with fertile agricultural soil,
pollination (by insects and birds), and clean water and air.[15] In addition, nature has its own inherent
worth, whether or not humans enjoy it or benefit from it. Proponents of that viewpoint believe we
should protect plant and animal species, regardless of their apparent human value. Furthermore many
people want future generations to inherit a world that retains some natural beauty and natural
resources.
This evolution in attitudes has led to the creation of a number of nonprofit organizations and government agencies focused on the environment. In 1970, the US Environmental Protection Agency
(EPA) was established.[16] The EPA’s function is to research, monitor, set standards, and enforce regulations to protect the environment. April 22 of that same year marked the first Earth Day, a worldwide
event intended to heighten awareness of environmental issues.[17]
Later in this chapter, we’ll review the many ways of protecting the environment by conserving natural resources, reducing pollution and waste, improving energy efficiency, and developing “clean” energy resources.
Nature and Human Health
In addition to their intrinsic value, natural landscapes do us good. However, Americans have become indoor
creatures. The trend toward dwindling outdoor time motivated journalist Richard Louv to write the 2005 book
Last Child in the Woods, which became a New York Times best seller and received an Audubon Medal. In it, he
describes the consequences of “nature-deficit disorder”: diminished creativity, overweight and obesity, attention deficit disorder, and depression.
Sedentary, indoor lifestyles are linked to adult chronic ailments such as cardiovascular disease as well as chronic childhood conditions such as obesity, attention-deficit/hyperactivity disorder, asthma, diabetes, and vitamin
D deficiency.[18]
Spending time outdoors improves health. A Canadian study showed that people who lived in greener neighborhoods got more exercise.[19] A study in children found that physical activity rose by 20 to 27 minutes a
week for each additional hour spent outside.[20] Furthermore, more outdoor time correlates with lower body
weight and less television viewing.[21]
Natural settings help relax us, relieve stress, stimulate the senses, reduce mental fatigue after prolonged concentration, and improve attention.[22] People with access to green spaces are less likely to suffer from depression and anxiety.[23] They also live longer.[24]
Fortunately, a number of organizations are working to increase children’s outdoor time.[25] Louv cofounded
the Children and Nature Network (http://www.childrenandnature.org), which works with health care providers, researchers, educators, organizations, and individual to get kids outdoors. Adults haven’t been left out
of this movement. Doctors are starting to prescribe outdoor activity as a means to maintain health, prevent
disease, and reduce the impact of chronic conditions.
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FIGURE 11.2 World Population Growth
This United States Census Bureau graph depicts world population from 1950 to 2050.
Source: US Census Bureau, International Data Base. World population: 1950–2050. 2012. http://www.census.gov/population/international/data/idb/
worldpopgraph.php.
1.2 Overpopulation: The Crux of the Problem
Overpopulation is the driving force behind environmental degradation. In the beginning, the human
population grew at a slow rate. The hunter-gatherer lifestyle kept the population in check. In 1650,
about half a billion humans walked the planet. Public health improvements, medical advances, and revolutions in agriculture and industry increased life expectancy. Between 1800 and 1930, the population
doubled from 1 to 2 billion.[26] By 1975—a mere forty-five years later—the population had again
doubled.
In October 2011, world population passed the 7 billion mark[27] and continues to swell at a rate of
200,000 people each day.[28] By 2050, over 9 billion people may crowd the planet.[29] The most rapid
development is concentrated in the poorest countries.
Population growth is a function of birth rates and death rates. If birth rates rise and/or death rates
fall, the population grows. If both occur, there will be more people and they will live longer. Crowding
leads to competition for land and water, typically at the expense of other species. Feeding and housing
an increased population leads to deforestation and overfished rivers and oceans. Development pollutes
air, water, and soil and consumes nonrenewable resources. Furthermore, overpopulation increases the
risk of infectious diseases and deepens conditions of poverty and disadvantage.
In short, overpopulation stresses the planet. In most ecosystems, populations control themselves.
When resources become overtaxed, species that depend on them die. Remove wolves and the deer population swells—until food shortages cause some animals to starve. Given that humans have the power
to limit their fertility, we have other options than famine, thirst, and war to control our numbers.
However, fertility rates lower than the "replacement" rate can also create social and economic
problems, in mostly in developed countries, where smaller working-age populations cannot support
the economy and meet the demands for social programs to care for the growing ranks of the elderly.[30]
Population growth depends on several factors:
1. Childhood mortality. In the developing world, parents often have more children, out of concern
that some may die. The motivation is to have enough offspring to work the fields and care for the
older generation. Many children in these countries die before age 5, mainly from infectious
illnesses.[31] Improvements in sanitation and hygiene, access to medical care and vaccinations,
and other factors have allowed more children to survive to adulthood. As child mortality rates
decline, parents may choose to have smaller families.
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2. Education. The most rapid population growth occurs in poor countries where largely uneducated
girls marry and begin bearing children in adolescence.[32] Education increases a woman’s social
status and earning power, allowing her to postpone marriage and childbearing. Although better
educated women tend to have fewer children, those children are more likely to survive because
they’re born into better socioeconomic conditions (less poverty, better hygiene, and increased
medical care).[33]
3. Access to contraceptives. According to Save the Children, an organization dedicated to
improving children’s lives, “222 million women have an unmet need for family planning.”[34]
Many of these women live in poverty in the developing world. While the net effect is reduced
fertility, contraceptive access has 3 effects on population. One, couples have fewer children. Two,
more children survive when births are adequately spaced. Three, fewer women die as a result of
pregnancy.[35] Meeting family planning needs lowers infant mortality an estimated 10 to 20
percent and maternal deaths by 35 percent.[36]
Contraceptives shift population demographics from high birth rate and high death rates toward
lower birth rates and death rates. The latter scenario leads to more stable and economically
prosperous societies. Overall, quality of life improves.
As a solution to overpopulation, Stanford University professor and author of The Population Bomb
Paul Ehrlich cofounded Zero Population Growth, now called the Population Connection. Sustainable
population growth depends on voluntary family-planning programs. To hold the population steady,
the average couple can have two children. For negative population growth, fertility rates need to decline further (assuming death rates stay constant).
Because fertility rates are highest in the developing world, organizations such as the United Nations Population Fund, the Population Connection, and Save the Children work to ensure that women
everywhere have access to affordable birth control. Because of the link between human overpopulation
and the extinction of other species, the Center for Biological Diversity created Endangered Species
Condoms. To see their clever advertising, go to http://www.endangeredspeciescondoms.com.
The United Nations also recognizes that governments need to take action to improve education
and women’s rights.[37] Furthermore, international protocols can commit nations to stabilize population growth.
Progress has been made. Since 1960, the global average birth rate has dropped from 6 children per
woman to 3.[38] As of 2014, birthrates range from 0.8 to 6.89.[39]
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1.3 Water: A Critical Environmental Resource
FIGURE 11.3
The Water Cycle
Source: John Evans/Howard Perlman/USGS. Water cycle. http://water.usgs.gov/edu/watercycle.html. 2005.
All organisms require water. However, the distribution of water on earth is uneven, leaving some areas
with precious little. Water covers 70 percent of the planet. The oceans hold about 96.5 percent of it, and
another 1 percent is also too salty to drink. About 2.5 percent is freshwater, including water held in glaciers and ice caps, underground, in lakes and rivers, and in the atmosphere. Only about 1.2 percent of
all freshwater is surface water, which serves most of life's needs.[40]
Water is constantly moving through the hydrologic (water) cycle. Surface water evaporates into
the atmosphere. Cooling as it rises, water vapor condenses into clouds and eventually returns to the
earth’s surface as precipitation. From there, it may become surface water and be stored in streams,
rivers, lakes, alpine snowpack and glaciers, oceans, manmade reservoirs, and wetlands (marshes, bogs,
swamps). In temperate regions, snowpack and glaciers serve an important reservoir for freshwater,
melting in the warmer months to feed streams and lakes.[41]
Precipitation may also penetrate deeper to become groundwater. Underground reservoirs called
aquifers store groundwater. We tap into aquifers for household, agricultural, and other uses. Of the
available freshwater, 99 percent is stored as groundwater.
Freshwater Shortages
According to the United Nations Environment Programme, 1.4 billion people live in river basins where
water use has outstripped the rate of replenishment.[42] Regions already facing water scarcity include
much of western North America, large regions of Africa, the Middle East, eastern Australia, South Asia,
and the North China Plain—all areas dependent upon irrigated agriculture. Millions of the people
affected are small farmers, who lack the means to move to moister climates.
Population growth and global warming will further strain this precious resource. Experts predict
that by 2025, more than 2.8 million people living in 48 countries will face water stress or scarcity.[43] By
2050, that number could rise to 4 billion people (40 percent of the projected global population).
Changes in temperature and precipitation as a result of global warming, as well as water pollution that
impairs the use of water, are expected to worsen regional water shortages in many parts of the globe.
People in poorer nations bear the brunt of the scarcity of clean fresh water. According to the
World Health Organization (WHO), 1.1 billion people in the developing world lack access to an
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HEALTH NOW VERSION 2.0.4
improved source of safe drinking water.[44] That’s 3.5 times the population of the United States. While
progress is being made under leadership from the United Nations, hundreds of millions of people are
at risk, and millions die each year from diseases attributable to lack of access to safe drinking water and
basic sanitation.[45]
In the United States, a surprising amount of our drinkable water is used to irrigate lawns, parks,
golf courses, and cemeteries. In Los Angeles, landscape irrigation use represents 54 percent of total
single-family water use.[46]
The average American goes through 152 gallons of water a day. Ironically, daily per-person use in
arid but emerald-lawned Phoenix in 2006 was more than 260 gallons. People in other developed countries get by with less. The average European manages on fifty-three to seventy-nine gallons a day.[47] In
contrast, in Mozambique, Africa, the average person has a mere 2.6 gallons a day—the amount that
goes down the drain during a 1-minute shower (with a low-flow showerhead) and one-hundredth of
the per person daily use in Tucson.
Ship lying aground in the former Aral Sea in
Kazakhstan.
Water Management and Conservation
Scientists, conservationists, and city planners are searching for ways to cope with looming water shortages. In Australia, where much of the bone-dry continent has struggled
with drought, the government has mandated restrictions on water use and has subsidized water tanks for homeowners to capture rainwater.
In addition, many Australian cities have spent billions of dollars on desalination
plants, which remove salt from seawater to render it potable (safe to drink).[48]
However, several of these plants has been idled as fresh water supplies have increased.[49] Israel has met its water needs through a heavy reliance on desalination.[50]
Some US cities, particularly in the arid Southwest, are also building desalination plants
in response to extended drought.[51] The process has also been used to improve the
quality of Colorado River water delivered to Mexico.[52] Opponents argue that the process is complicated, costly, harms marine ecosystems, and consumes energy, which further contributes to global warming and, hence, drought.[53]
Source: Staecker. Orphaned ship in former Aral Sea.
Some experts prefer other measures, such as water recycling, which has a smaller
http://commons.wikimedia.org/wiki/File:Aralship2.jpg. 2003.
economic and environmental impact. As described earlier, nature constantly recycles
water. Humans have also long recycled water. For instance, water diverted from creeks
and rivers to irrigate agricultural land eventually returns to surface and ground water systems.
However, that water often contains pesticides, synthetic fertilizers, and salts leached from the soil.
Increasingly, waste water from municipal sewage systems has become a source of water. This reclaimed water can be used to irrigate crops and urban landscapes, flush toilets, and replenish groundwater aquifers. Industries can recycle and reuse water on site. Rapidly evolving treatment technology
removes biological and chemical pollutants to make the water potable (safe to drink).[54] Concerns remain about the ability to remove certain contaminants, such as pharmaceuticals.[55] While no health
problems have been reported, public acceptance has lagged behind the technology.
A different form of recycling is capturing and reusing gray water—water used for bathing,
showers, dishwashing, and clothes washing. This reclaimed water can irrigate outdoor areas. To protect
plants, soap and other personal care products need to be nontoxic and low in sodium.[56]
The city of Tucson, Arizona, has adopted an ordinance requiring that new residential units be
plumbed to divert gray water for irrigation.[57] Using reclaimed water instead of drinking water for irrigation saves enough water every year for more than 60,000 families.[58]
Other Western states such as Colorado and California are taking steps to conserve freshwater.[59]
In April, 2015, the governor of California directed the State Water Resources Control Board to implement mandatory water reductions to reduce urban water usage by 25 percent.[60] Means of accomplishing this goal include restricting lawn watering, adopting tiered water rate structures that increase
the cost per gallon as more water is used, and providing incentives for homeowners to install more efficient plumbing fixtures and drought-tolerant landscaping. Farmers can be encouraged to reduce wasteful flood irrigation and, in some cases, to reduce their water demands and/or temporarily fallow some
irrigated lands.
Conservation works. Boston’s efforts to conserve water (fix leaks in aging pipes, install low-flow
shower heads and toilets) reduced water demands between 1980 and 2009 by a whopping 43 percent.[61]
Assess Yourself: How Can You Conserve Water?
If Europeans can maintain a high standard of living on half the water, we can surely follow suit. Because much
municipal water goes to home use, citizens have the power to conserve this precious resource.
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Examine the following list. Check off the things you’re doing now. Resolve to adopt one new water-conserving
habit. If you live in a dormitory, some goals may have to wait until you have your own place.
____ I turn on the tap only when I really need water. I turn it off while I’m washing dishes, brushing my teeth,
shaving, and soaping up in the shower (and I turn it on only to rinse).
____ When hand-washing dishes, I fill a basin with soapy water and another with rinse water. I don’t leave the
tap running. (Note: Compared to hand washing, dishwashers use a lot less water.)
____ I promptly repair leaky faucets.
____ I shower rather than bathe.
____ I take short (five minutes or less) showers.
____ My showerhead is a low-flow fixture. (Before 1992, fixtures delivered 5.5 gallons a minute. The federal
government has mandated that new fixtures can’t exceed 2.5 gallons a minute.[62] To find out the rate of
yours, time how many minutes it takes to fill a one-gallon bucket.)
____ I have a low-flow toilet. (Toilets account for more than one-third of home water use.[63] Pre-1980 models
use anywhere from 3.5 to 7 gallons per flush. Ultra low-flush toilets use 1.6 gallons per flush. To reduce the
flow of your toilet without buying a new one, drop a few pebbles into an empty liter bottle, fill with water, and
place in the toilet’s tank.[64] )
____ I use a front-loading washing machine (which is water and energy efficient) and a water-efficient
dishwasher.
____ I wait to run the dishwasher and washing machine until I have a full load.
____ I water houseplants with “gray water.”
____ When I landscape, I select plants resistant to drought. (That’s important if you live in an arid region.)
____ I make sure outdoor yard irrigation systems water efficiently (during cooler times of the day with no to
little runoff on pavement).
____ I take my car to a car wash rather than using a hose to wash it myself. (Going to the car wash uses less
water. Municipal car washes are usually required to recycle water.)
____ I eat foods that require less water to produce—more fruits and vegetables, less meat, dairy, and processed foods.
____ I recycle paper, plastic, glass, and metal. (More water is used in creating these materials from their raw
materials than from recycled products.)
1.4 Pollution: Problems and Solutions
Pollution is defined as the introduction into the environment of substances with harmful effects.
Physical, chemical, and biological alteration of air, water, and soil, including the introduction of toxic
substances, can sicken us and other living creatures. Many of the pollutants discussed in this section are
man-made.
Water Pollution
Degradation of water quality is a major concern worldwide. The pollution of freshwater sources and
the oceans from the discharge of human, industrial, and agricultural waste has enormous implications
for human health and the health of natural ecosystems. The absence of sanitation facilities results in the
contamination of drinking water sources around the globe, particularly in Asia and Africa. Microbes in
drinking water cause infectious diseases, mainly diarrheal illness, and represent the number one cause
of death in children under five years old. According to the WHO, “More people die from unsafe water
annually than from all forms of violence, including war.”[65]
Freshwater fish and aquatic insects, plants, and animals are adversely affected by the discharge of
pollutants, warmer water temperatures (often from power plants), and the destruction of wetlands that
naturally filter out contaminants and provide important wildlife habitats. Loss of habitat and changes
in the chemical and biological characteristics of rivers and streams can lead to reduction in species
abundance and diversity. Freshwater species populations have suffered a 76 percent decline in the last
40 years.[66]
Marine life has suffered too. Pollution, warmer water temperatures, and overfishing have stressed
our oceans. Records tracking some 217 species of marine mammals, birds, reptiles, and fish show pronounced declines over the past 4 decades.[67] For a graphic created by the World Wildlife Federation,
go to http://www.unep.org/dewa/vitalwater/article161.html.
© 2013 Flat World Knowledge, Inc. All rights reserved.
Pollution
The introduction into the
environment of toxic
substances (pollutants) that
have adverse effects on living
organisms and natural
resources.
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In 1972, the United States enacted the Clean Water Act, which authorized the EPA to implement
pollution controls. The result of that law and subsequent amendments has been a significant improvement in the quality of surface water sources in the country. However, many challenges remain, including controlling chemicals from urban and agricultural storm water runoff and adequate regulation of
surface and ground water pollution from oil and gas drilling.[68] According to EPA assessments, 54
percent of river and streams are impaired by problems such as microbial pathogens and pollution.[69]
Plastics and Human Health
Plastics are versatile, useful, pervasive, and, in many ways, unhealthy. On and around your own desk you may
have multiple plastic-derived objects: insulation in the computer cables; CDs; the printer ink; the lenses of your
glasses; and the casings of your phone, monitor, mouse, pens, and the keyboard under your fingertips. It’s in
containers that hold food, beverages, personal care products, and cleaning agents. It’s in dental sealants, water
pipes, toys, plastic cutlery, glue, clothes, and building materials.
Derived from natural gas and crude oil (petroleum), plastics are synthetic polymers (long chains of repeating
units made from carbon, hydrogen, and other atoms). Worldwide production of plastics is more than 600 billion pounds and is increasing at a rate of 4 percent per year.[70] More than 5 percent of the world’s crude oil
production goes into the production of plastics.[71]
Certain types of plastic contain endocrine disruptors—substances that alter normal hormonal function. A prime
example is bisphenol A (BPA). Phthalates are plasticizers (substances added to materials to make them more
flexible). Other man-made sources of endocrine disruptors include industrial solvents/lubricants
(polychlorinated biphenyls, polybrominated biphenyls, dioxins), plastics (bisphenol A), plasticisers (phthalates),
pesticides, and some heavy metals (mercury, lead). These chemicals enter our bodies when we ingest them in
food and beverages, inhale them, and apply them to our skin.
Exposure during fetal development and infancy may be particularly detrimental. A study showed that 93 percent of breastfed infants had BPA in their urine.[72] Scientists have raised concerns that endocrine-disrupting
chemicals affect brain and behavior; alter the development of the immune system, hasten the onset of puberty; impair fertility; retard fetal growth; and raise the risk for obesity and some cancers.[73] [74] [75] [76]
Here’s how you can reduce your exposure harmful chemicals in plastics:
<
Avoid these products:
<
<
<
<
<
<
<
<
<
<
plastic containers marked on the bottom with “7” or “PC” (for polycarbonate), which contain
BPA
hard, clear plastic containers not labeled as BPA-free
plastic-wrapped foods such as deli meats and cheeses
Choose canned foods labeled BPA-free. (BPA is often used to line the inside of cans.)
Drink beverages in glass or steel containers.
Store food in ceramic or glass containers.
Microwave food in ceramic or glass containers, not plastic.
Wash plastic beverage and food containers by hand in lukewarm water rather than in the dishwasher.
Use wood rather than plastic cutting boards.
Use plant-derived fragrances. Synthetic fragrances usually are phthalates.
If you have a baby, use glass bottles with nipples that don’t contain phthalates. Don’t accept hand-me-downs
that may contain them. The same is true for toys marked with a “3” or “PVC,” which stands for polyvinyl chloride. In 2012, the Food and Drug Administration banned BPA from baby bottles and “sippy cups.”[77] The FDA's
position is that at current levels of exposure, BPA is safe in food containers such as cans and water bottles.[78]
[79]
For more ideas, check out “Eat like a Mennonite,” a New York Times personal essay on avoiding BPA and phthalates (http://www.nytimes.com/2013/01/19/opinion/eat-like-a-mennonite.html?ref=opinion&_r=0).
Air Pollution
The atmosphere enveloping the earth is divided into five layers. This chapter will focus on the first two:
the troposphere and the stratosphere. The troposphere begins at sea level and extends upward seven
miles, becoming cooler and thinner in water vapor and life-sustaining gases as it rises. Only the bottom
third—just over 2 miles—is breathable.[80] What we call “weather” occurs in the troposphere.
Parallel to the junction between the troposphere and the stratosphere are strong wind currents
called jet streams. The predominant wind direction is west to east. The jet streams influence weather
and airplane travel. The outer edge of the stratosphere contains ozone, a gas formed from the
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interaction of the sun’s ultraviolet rays and oxygen. Stratospheric ozone shields life on earth’s surface
from the harmful effects of ultraviolet radiation. As we’ll soon discuss, depletion of stratospheric ozone
and excess tropospheric ozone damage health.
Sources of air pollutants are both natural and man-made. Natural causes include forest fires, volcanic eruptions, dust storms, decaying organic matter in swamps, fungal spores, and pollen blooms.
Most of the time, these natural air pollutants are minor in comparison to human-generated sources. All
of our modes of transportation—train, car, truck, airplane—produce pollution from the combustion of
fossil fuels. Power plants, industrial facilities, and modern agriculture also release particles and gases
that are harmful to humans. Tobacco smoke and wood smoke from fireplaces pollute indoor and local
outdoor air.
According to the WHO, indoor air pollution causes 2 million premature deaths a year; urban outdoor air pollution leads to 1.3 million deaths a year.[81] Respiratory illnesses account for many of these
deaths.[82] Children, older adults, and people with lung disease are most vulnerable.
Air pollution is especially a problem in India and China, where rapid economic development has
increased the use of fossil fuels such as coal for generating electricity, heating homes, and powering industrial plants.[83] Air pollution in one region can affect the entire planet because winds transport pollutants to distant locations.
In 1963, the US government enacted the Clean Air Act, which originally funded research into
techniques for monitoring and controlling air pollution. Major amendments to the Act in 1977 and
1990 strengthened the role of the EPA to monitor and enforce regulations on air pollutants. The EPA
calculates outdoor air quality using the Air Quality Index (AQI) for the 5 major air pollutants: particulate matter, sulfur dioxide, nitrogen oxide, ozone, and carbon monoxide. The Clean Air Act regulates
these pollutants, and the EPA establishes standards to protect public health. AQI values run from 0 to
500. The lower the number, the better the air quality.
TABLE 11.1 Air Quality Index (AQI)
Air quality index (AQI) range
Air quality condition
Color
0–50
Good
Green
51–100
Moderate
Yellow
101–150
Unhealthy for sensitive groups
Orange
151–200
Unhealthy
Red
201–300
Very unhealthy
Purple
301–500
Hazardous
Maroon
Note: The EPA divides AQI values into six categories, ranging from good to hazardous air quality. The
category called “Unhealthy for Sensitive Groups” refers to children, older adults, and people with heart
and lung disease.
Source: AIRNow/Environmental Protection Agency. Air Quality Index (AQI): a guide to air quality and your health. http://www.airnow.gov/
index.cfm?action=aqibasics.aqi. 2011.
The 4 Most Damaging Air Pollutants
Particulate matter is made of small particles suspended in the air in dry form or mixed with liquid
droplets. Natural sources include dust, sea salt spray, smoke from wildfires, volcanic ash, pollen, fungal
spores, and airborne bacteria and viruses. Man-made sources include aerosols and chemical fumes.
These fine particles make the air hazy, reducing visibility. They stain and corrode statues, monuments, and other structures. Wind carries suspended particles long distances. Eventually they settle to
the ground, damaging plants and polluting soil and water.
The tiniest particles (those less than ten microns in diameter) can be inhaled into the lungs to irritate the airways, leading to bronchitis, asthma attacks, decreased lung function, irregular heartbeat, and
premature death.[84] Chronic exposure contributes to cardiovascular and respiratory diseases, including lung cancer.
Sulfur dioxide is a colorless gas that smells like a burnt match. In the presence of water vapor, it
turns into a mist of sulfuric acid.[85] Manmade sources stem from the combustion of fossil fuels in
power plants, iron and steel mills, pulp and paper mills, and petroleum refineries. Exposure irritates the
eyes and inflames and narrows respiratory passages, triggering coughing and asthma symptoms. Sulfur
dioxide can also react with other compounds to form small particles that can damage the lungs. When
combined with water vapor, it forms sulfuric acid, leading to acid rain.
Nitrogen oxides are formed from nitrogen and oxygen. Nitrogen dioxide is the predominant
chemical. This reddish-brown, strong-smelling gas arises from combusting fuels to generate power,
heat homes, and run motorized vehicles. People who live or work near roadways are at particular risk
for exposure. This gas inflames the eyes, nose, throat, and respiratory tract. Long-term exposure reduces lung function and triggers airway inflammation, especially in asthmatic children.[86] Like sulfur
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oxides, nitrogen oxides can become acidic components of particulate matter, thereby contributing to
acid rain.
Ozone is an unstable molecule made of three oxygen atoms. This gas is colorless and odorless. In
the troposphere, ozone results primarily from chemical reactions involving sunlight and gases generated by the burning of fossil fuels: nitrogen oxides, carbon monoxide, methane, and other hydrocarbons (compounds made of hydrogen and carbon).[87] Ground-level ozone levels tend to peak in cities
on hot, sunny days. Ozone irritates respiratory linings, triggering asthma and causing sore throat,
coughing, pain upon deep inhalation, and shortness of breath.[88] It also damages plants and reduces
crop yields, further challenging the ability to feed the world’s growing population.[89] Between the
1860s and the 2000s, ground-level ozone increased fourfold.
FIGURE 11.4 Antarctic Ozone Hole on
July 16, 2015
Ozone Hole Changes
Stratospheric ozone shields earth’s inhabitants
from the sun’s ultraviolet light. Use of
compounds called chlorofluorocarbons has
thinned the ozone over the South Pole. Purple
and blue colors represent areas of the least
ozone.
The size and shape of the ozone hole is constantly changing. Watch this animation showing
the ozone hole changes from July 1 to December 31, 2014:
Source: National Aeronautics and Space Administration
Goddard Space Flight Center.
http://ozonewatch.gsfc.nasa.gov/Scripts/
big_image.php?date=2015-07-16&hem=S. Published with
permission.
ozone hole
A region of marked thinning
in stratospheric ozone.
http://ozonewatch.gsfc.nasa.gov/ozone_maps/movies/
OZONE_D2014-07-01%P1D_G^1280X720.MMERRA_LSH.mp4.
Stratospheric Ozone Depletion: The Ozone Hole
Ozone levels have increased in the troposphere, where at ground level this gas causes
serious health problems. In the stratosphere, where it shields us from ultraviolet light,
ozone has been depleted. The main culprit is chlorofluorocarbons (CFCs), compounds
made of carbon, chlorine, hydrogen, and fluorine. They were invented in the 1920s for
use in propellants (including aerosol sprays), refrigerants, cleaning solvents, and foaming agents.[90] In the 1970s, scientists established a link between CFCs and ozone depletion. An expanding region of marked thinning over Antarctica was called the ozone
hole. (A smaller ozone hole exists over the North Pole.) By 1984, about 40 percent of
the stratospheric ozone had been lost.[91]
Consequences of depleted ozone stem from an increase in ultraviolet (UV) light
reaching the ground and oceans. Scientists are concerned about damage to terrestrial
plants and phytoplankton, which supports marine life.[92] [93] Excess UV radiation also
decreases the productivity of terrestrial plants. In humans, increased exposure to UV
rays suppresses immune function and heightens the risk of sunburn, skin cancer, and
cataracts (vision-impairing cloudiness in the eye’s lens). Because they live under the
ozone hole, Australians have the highest rates of skin cancer.[94]
Beginning in the late 1980s, international protocols such as the Montreal Protocol
were established to reduce and eventually ban the production of CFCs. Since then, stratospheric concentrations of ozone-depleting chemicals have steadily declined.
Indoor Air Pollution
In addition to air pollutants that enter buildings through doors and windows, other
sources can pollute indoor air. Common examples include wood and coal-burning stoves, furnaces,
lead, tobacco smoke, radon, mold spores, cleaning products, and off-gassing building materials.
The most prevalent indoor pollutant is tobacco smoke. It contains hundreds of toxic chemicals, including poisonous gases (carbon monoxide, hydrogen cyanide, ammonia, butane, toluene), carcinogens (formaldehyde, benzene, vinyl chloride), and toxic metals (arsenic, lead, and cadmium).[95]
Carbon monoxide is a colorless, odorless gas formed from incomplete combustion of natural gas,
oil, coal, wood, tobacco, and other carbon-containing materials. Each molecule is made of one carbon
and one oxygen atom (CO). (Carbon dioxide, on the other hand, contains two oxygen atoms.) Carbon
monoxide binds tightly to hemoglobin, a protein in red blood cells that normally transports oxygen to
tissues. The result is reduced oxygen delivery. Carbon monoxide poisoning causes headache, dizziness,
fatigue, weakness, nausea, vomiting, and eventually death. The skin and mucous membranes redden.
Proper ventilation reduces exposure. Living spaces should have carbon monoxide detectors that set
off an alarm when at critical levels. If yours goes off, go outside and breathe fresh air. Leave windows
open until you can get a professional inspection. Never leave your car idling in a garage or other poorly
ventilated space.
In addition to carbon monoxide, formaldehyde pollutes indoor air when released by materials
such as carpets, particleboard, plywood, furniture, and adhesives. Workers in industries making these
products are most at risk. Short-term effects include nausea; skin irritation; and burning of the eyes,
nose, and throat. Long-term exposure has been associated with some types of cancer.[96]
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Lead, a naturally occurring metal, can contaminate air as well as water and soil. Sources include
plants that process ores and metals and make lead-acid batteries. In the past, motor vehicles fueled by
leaded gasoline were a major source of atmospheric lead. Homes built before 1978 may have lead-based
paint.[97] Over time, the paint chips away, turns to dust, and settles onto floors and outdoor soil.
Nonplastic plumbing installed before 1986 also contained lead. Corroded pipes then release lead.
The EPA recommends that, if the tap hasn’t been turned on for six hours or more, run the water until
it becomes cold.[98] Because lead is used in ceramic glazes, imported pottery is another source. For
more information about protecting yourself from lead, consult the EPA website (http://www.epa.gov/
lead/parents.html#soil).
Lead enters the body when inhaled, ingested, or applied to the skin. It damages the nervous system, blood, kidneys, and other tissues.[99] Children are especially vulnerable to impaired brain development.[100] For that reason, use of lead in paint, in plumbing, in shotgun pellets (for hunting fowl), and
as an additive to gasoline was eventually banned.
Radon is a naturally occurring odorless, colorless, tasteless, radioactive gas that comes from
breakdown of uranium. Indoor radon ranks second to tobacco smoke as a cause for lung cancer and
results in over 21,000 lung cancer deaths a year.[101] Sources include soil, rock, and, less often, well water. Radon in the ground under buildings or in building materials seeps into indoor air where it can be
inhaled. People may also ingest it in contaminated water. The only way to determine whether this gas is
in your home or workplace is to test the levels. You can find kits at hardware stores. Sealing cracks in
foundations, basement floors, and walls can reduce radon. If it doesn’t, ventilation systems may be
needed.
Asbestos is another cancer-causing substance that can contaminate indoor air. This mineral fiber,
which occurs naturally in rock and soil, has been used for insulation and as a fire retardant. It’s found
in products such as heat-resistant fabrics, building materials (shingles, vermiculite insulation, ceiling
and floor tiles, walls and floors around wood-burning stoves, some cement products), and motor
vehicle parts (breaks, transmission, clutch).[102] If asbestos was used in cement water mains, it can decay into drinking water.
When asbestos-containing products are disturbed (during installation or demolition), fibers can be
released into the air. People who inhale the fibers may eventually develop lung cancer, mesothelioma
(cancer of the lining of the chest organs), and asbestosis (a noncancerous, chronic lung disease). Many
asbestos products and uses are prohibited in the United States, but others are still permitted.[103]
If you suspect you have asbestos in your home, find out how to protect yourself on the EPA website (http://www.epa.gov/asbestos/protect-your-family.html).
Radon
A naturally occurring
odorless, colorless, tasteless,
radioactive gas derived from
the breakdown of uranium.
Asbestos
A natural mineral fiber that
was used for insulation and
as a fire retardant. If inhaled,
the fibers can eventually
cause lung cancer and other
chest diseases.
What You Can Do to Reduce Air Pollution
Granted, a lot of air pollution comes from power plants and other industrial sources. But individual actions,
such as driving automobiles and heating homes, also play a powerful role. Here’s what you can do:
<
<
<
<
<
<
<
<
<
Keep your car well-maintained and use it only when necessary.
Avoid idling your car (unless you’re waiting at a traffic light).
Support the production of electricity that’s not generated by coal-fired plants, which are a major
source of air pollution. Some utilities offer programs in which ratepayers can elect to purchase energy
from renewable sources.
Test your home for radon. The EPA website has information about testing for radon and reducing
home levels of this gas at http://www.epa.gov/radon/index.html.
Don’t smoke!
Use water-based paints, stains, and paint strippers. Avoid those high in toxic volatile organic
compounds (“VOCs”—toxic solvents that evaporate into the air).
Use carpets and other building materials that are low in VOCs.
Conserve energy. While the contribution from renewable sources is increasing, the United States still
relies largely on fossil fuels for energy. So when you use electricity, you’re contributing to the burning
of fossil fuels.
Consider the life-cycle energy cost of products that you buy, including processing, packaging, and
transportation that consume energy and release pollutants.
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HEALTH NOW VERSION 2.0.4
Land Pollution and Solid Waste
Much household solid waste ends up in
landfills, disposal sites where trash is buried
between layers of dirt.
Source: Ashley Felton. Active tipping area of an operating
Some pollutants are first introduced into the environment on the land. For instance,
synthetic pesticides and fertilizers applied to crops also contaminate the soil. Precipitation carries those pollutants into surface and groundwater. Soil pollutants may also become incorporated into dust, which becomes airborne when blown by the wind and is
redeposited elsewhere on the earth or in the oceans. Air pollutants from industries and
vehicle exhaust will also eventually settle to the surface.
In addition, most of our municipal solid waste (trash) ends up in landfills. In a
single year, Americans throw away about 254 million tons of trash.[104] Containers and
packaging constitute one-third of solid waste.
Although we dump most of our trash in landfills, we’re getting better at reducing
that waste. Nearly 12 percent of solid waste is combusted for energy. About 34 percent
is recycled or composted, a number that has crept steadily upward thanks to
heightened public awareness, increased infrastructure, and a growing market demand
for recycled materials.
FIGURE 11.5 Enormous opportunities for recycling and composting
landfill in Perth, Western Australia.
http://commons.wikimedia.org/wiki/File:Landfill_face.JPG.
2006.
Source: Adapted from Environmental Protection Agency. What happens to the stuff we throw away. Recycling Basics. http://www2.epa.gov/recycle/
recycling-basics.
The EPA defines recycling as “the recovery of useful materials, such as paper, glass, plastic, and metals,
from the trash to use to make new products, reducing the amount of virgin raw materials needed.”[105]
Composting involves collecting organic waste (e.g., food scraps and yard clippings) and storing it under conditions that promote the breakdown of the material. Once the process is completed, compost
can be used as a rich fertilizer.
Americans are best at recycling paper (a rate of 67 percent) and worst at recycling plastic containers and packaging (overall 9 percent).[106] About 34 percent of metals (aluminum, steel, and mixed
metals) are recycled.
The benefits of recycling and composting are multiple and include the following:
less waste taxing our landfill capacity
< conservation of the raw materials from which these products are composed
< reduced energy consumption and pollution involved in collecting and processing raw materials
(A total of 87 million tons of solid waste recycled in 2012 reduced carbon dioxide emissions by
168 million metric tons, equivalent to removing 33 million cars from the road.[107] A 2009
mandatory recycling and composting ordinance in San Francisco led to a 12 percent reduction in
the city’s carbon emissions compared to 1990;[108] it plans to be a zero-waste city by 2020.)
<
<
job creation in recycling and manufacturing industries[109]
Two other strategies help us conserve resources and protect the environment: reduce and reuse. A
good way to minimize your environmental impact is to buy fewer goods. Consider sharing with friends
and neighbors large items such as lawn mowers, power tools, clothes washers, and cars. Rent rather
than buy infrequently used goods. Choose products with less packaging.
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In addition to reducing your use of resources, you can reuse products already in circulation. Bring
fabric bags to stores. Buy used goods. Donate items so others can reuse them. Repair items rather than
tossing and replacing them. Build using refurbished materials. Buy products made from recycled materials, which supports the market for recycling.
Video Clip 17.1
Making Music on Recycled Materials
Landfill Harmonic is a 2014 documentary about Cateura, Paraguay, a town built on a landfill. To keep kids away
from gangs and drugs, a school music program was started, using instruments made from recycled materials.
View the video online at: http://www.youtube.com/v/fXynrsrTKbI
Assess Yourself: Do You Reduce, Reuse, and Recycle?
Are you doing all you can to conserve valuable resources? Check off the things you’re already doing and
identify at least one new habit you could adopt.
____ I buy goods that last.
____ I buy reusable rather than disposable items (e.g., pens, razors, silverware, cups).
____ I recycle aluminum, glass, plastic, paper, batteries, and electronic equipment.
____ I carry beverages in reusable containers and bring my own cup to coffee shops.
____ I bring reusable bags when shopping.
____ I shop for minimally packaged products (or choose packaging made from recycled materials).
____ I shop for products made from recycled materials.
____ I repair items such as shoes, clothes, cars, and appliances so that they last longer.
____ When possible, I buy durable goods that are gently used rather than new. (The manufacture of new
goods consumes energy and water.)
____ I donate my used books, clothing, furniture, and electronics.
____ I buy rechargeable batteries for devices I use frequently.
____ I compost organic matter—food waste, lawn clippings, leaves. (To learn how, go to
http://howtocompost.org.)
In addition to the relatively nontoxic items we routinely toss, there are also hazardous wastes, those
capable of harming humans and the environment. Household materials that qualify include batteries,
motor oil, gasoline, antifreeze, paint, paint thinner and other solvents, and compact fluorescent bulbs
(which save energy but contain small amounts of mercury). Some industrial materials are highly toxic,
such as radioactive materials used in medicine and nuclear power plants.
One approach is to minimize your use of toxic products. For instance, you can buy paints lower in
toxic chemicals and cleaning products made from biodegradable (decomposed by bacteria), nontoxic
materials. You should also take batteries, electronic equipment, and other hazardous materials to collection centers for disposal. Do not dispose of hazardous wastes down the sink, into storm sewers, onto
the ground, or in the trash. Doing so pollutes soil, water, and air. Your municipal recycling center can
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tell you where to take them. To find out more about recycling of nonhazardous and hazardous materials, consult Earth911.com or http://www.epa.gov/epawaste/basic-hazard.htm.
Light and Noise Pollution
FIGURE 11.6
The city lights, such as those in Spain and Portugal, can disrupt daily rhythms in humans and animals.
Source: NASA. Iberian Peninsula at night—NASA Earth Observatory. http://commons.wikimedia.org/wiki/
File:Iberian_Peninsula_at_Night_-_NASA_Earth_ Observatory.jpg. 2011.
When we talk about pollution, most people think of harsh chemicals. However, light and sound also
have profound effects on living creatures.
Light pollution is excessive or intrusive amounts of light. Recall from Chapter 6 that darkness
helps us sleep. Light, even small amounts emitted by electronic devices, inhibit the nighttime rise in
melatonin, a hormone that regulates many cycles, including sleep. Breast cancer risk has been reported
to be higher among women who work night shifts and live in communities where artificial lighting is
bright enough to read outdoors at night.[110] Urban lights also obscure our view of the night sky. Just
think about how much better you see stars and planets when you’re far from a city.[111]
Plants and animals are also affected by artificial light. It can hinder the normal adaptation of trees’
and other plants’ seasonal variations in natural light. In animals, artificial light can interfere with normal daily rhythms, nighttime navigation, breeding cycles, and foraging behaviors.[112]
Outside lights, especially those that point sideways and upward, are the main causes of light pollution. A solution is to install lights that angle downward or that are activated by motion (turning on
only as someone approaches your home).
Noise pollution involves the production of sounds loud enough to adversely affect the health of
humans and other animals. If you live in an urban area (or even in a college dormitory), you understand that loud music, construction, honking cars, and sirens can be more than an annoyance. Loud
noises disrupt sleep, fracture concentration, shatter peace of mind, generate stress (which is particularly hard on the cardiovascular system), and impair hearing.
A 2011 WHO report stated that environmental noise was second to air pollution in causing human disease, death, and disability.[113] Listening to MP3 players at high volumes has led to hearing loss
in many teens and young adults. Earbud-style earphones increase the decibel (sound level) exposure.
Fifteen percent of college graduates have hearing loss on par or worse than that of their parents.[114]
Many land animals use sound to communicate, navigate, and find food.[115] Our noise can disrupt
these processes. The ocean has also become a noisy place due to underwater blasts, sonar and seismic
surveys, shipping, and oil and gas industry activity. Marine mammals (whales, dolphins, and porpoises) that navigate and communicate using sound have been most adversely affected.[116]
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Here’s some sound advice: take care of your ears. Prolonged exposure to loud noises leads to tinnitus (ringing or buzzing in the ears) and permanent hearing loss. If you use a head set when listening
to music and movies, use the kind that goes over your ears instead of earbuds. Keep the volume at a
moderate level. Rather than turning up the tunes to drown out the noise around you, listen to lowervolume music with noise-canceling headphones. Wear ear protection (ear plugs, ear muffs, noise-reducing headset) when exposed to loud noises: attending loud concerts, riding or working on a motorcycle, or operating power equipment (chainsaw, jackhammer, lawnmower).
TABLE 11.2 How Loud Is Too Loud?
Decibels
Sound source
150
Firecracker
120
Ambulance siren
110
Chain saw, rock concert
105
Personal stereo system at maximum level
100
Wood shop, snowmobile
95
Motorcycle
90
Power mower
85
Heavy city traffic
60
Normal conversation
40
Refrigerator humming
30
Whispered voice
0
Threshold of normal hearing
Note: The National Institute on Deafness and Other Communication Disorders provides a scale of noise
levels. Sound intensity is measured in decibels. Prolonged exposure to sounds at 85 decibels leads to
hearing loss. Higher decibel levels more quickly damage hearing. Only one minute at 110 decibels can
permanently impair hearing.
Source: National Institute on Deafness and Other Communication Disorders (NIDCD). How loud is too loud? http://www.nidcd.nih.gov/health/
hearing/pages/ruler.aspx.
K E Y
<
<
<
<
<
<
<
T A K E A W A Y S
Environmental health began in an attempt to reduce exposure to infectious diseases. The field has since
broadened to include all external factors (chemical, biological, and physical) that can potentially affect
health.
Industrialization and rapid population growth accelerated the use of natural resources and the release of
toxic compounds into the environment. Governments subsequently have enacted legislation to regulate
pollution.
Controlling population growth is critical to solving environmental problems.
Freshwater is a limited resource. Looming water shortages make water conservation critical.
Byproducts from burning fossil fuel are largely responsible for outdoor air pollution. Indoor air pollutants
include tobacco smoke, chemicals in building materials, solvents, cleaning products, and radon.
People can minimize solid waste production by buying fewer consumer goods, recycling, and reusing
materials. Doing so also reduces pollution and consumption of natural resources.
Light and noise pollution, though under-recognized, have a significant impact on health.
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D I S C U S S I O N
Q U E S T I O N S
1. Modern humans spend little time in natural environments. What does “being in nature” mean to you?
How much time do you currently spend outside each week? Describe what you do. Do you ever go
outside as a study break? If yes, how do you feel afterward? Is there a qualitative difference between being
in an urban green space (a backyard or park) and a wilder natural setting (national park, wilderness area,
ocean)?
2. Consider the concept of environmental stewardship. Some people dismiss the concept as speciesist
(discriminates based on species) or anthropocentric (assumes humans are the most important species).
Others insist that we humans, who have so degraded the environment, have moral and ethical obligations
to lessen the damage and protect nature.
What do you think? What does environmental stewardship mean to you? Should we protect natural
environments? For whom? Future generations of humans or all future life forms? Should we preserve
species even if doing so might threaten human interests? (Examples include large predators.)
3. Go to this National Geographic website: http://environment.nationalgeographic.com/environment/
freshwater/water-footprint-calculator. Calculate your “water footprint.” View the tips. What did you learn?
Can you reduce your water use? How will you accomplish that goal? (Note: when you finish the
calculation, click the link at the bottom that takes you to “Water Footprint Calculator Methodology and
Tips.”)
4. Go to the AIRNow website (http://airnow.gov). In the forecast tab, do you see any American cities with an
air quality index worse than moderate? Click on the map over your region for more detailed information.
How is your air quality today?
5. Go to http://www.epa.gov/aircompare/index.htm. Click on “County Comparisons.” Compare the county in
which you live to another city you suspect might have worse air quality. How did your county stack up?
6. In addition to being a potent source of indoor air pollution, tobacco has other environment downsides.
Go to this World Health Organization website: http://www.who.int/tobacco/research/economics/
rationale/environment/en/. Summarize what you learned about the environment degradation associated
with growing and producing tobacco products.
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2. CLIMATE CHANGE: CAUSES AND CONSEQUENCES
L E A R N I N G
1.
2.
3.
4.
O B J E C T I V E S
Explain the greenhouse effect.
Differentiate between renewable and nonrenewable energy resources.
Review the evidence for climate change and the consequences of global warming.
Examine ways groups and individuals can reduce greenhouse gas emissions.
FIGURE 11.7 How the Earth’s Greenhouse Effect Works
Source: Adapted from NOAA; Conway T, Belnay L. How the earth’s greenhouse effect works. http://www.esrl.noaa.gov/gsd/outreach/education/
climgraph/CG_Figure_16.gif.html.
Life as we know it depends on the temperature of the land, air, and oceans. Temperature variations
affect the range of plants and animals. They also shape weather patterns. The source of warmth is the
sun. After it penetrates the atmosphere, some of the sun’s energy is absorbed by the earth and some is
radiated back into space.
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Greenhouse gases
Gases that absorb heat
energy in the atmosphere.
These include carbon dioxide,
methane, and water vapor.
greenhouse effect
The phenomenon whereby
atmospheric gases such as
water vapor, carbon dioxide,
and methane trap solar
radiation and consequently
warm the earth’s surface.
global warming
Increase in the earth’s
temperature.
carbon cycle
A combination of processes
by which carbon-containing
compounds move between
different reservoirs—the
atmosphere, oceans, and
living organisms.
HEALTH NOW VERSION 2.0.4
Greenhouse gases absorb heat energy in the atmosphere. Without them, the earth would be a
frozen, inhospitable place. Prime examples include carbon dioxide (CO2), methane, and water vapor,
which trap heat much as the glass does in a manmade greenhouse. The atmospheric concentration of
these gases changes the temperature of the planet through a complex mechanism known as the greenhouse effect.
A net increase in these gases enhances the greenhouse effect. The end result is global warming, a
term describing the increase in the earth’s temperature. The other term for this phenomenon is climate
change. (Climate refers to average weather patterns over a long period of time.)
Carbon dioxide is the greenhouse gas that contributes to most of the enhanced greenhouse effect.
Historically, carbon dioxide levels were fairly stable (barring the occasional volcano). Then came the
Industrial Revolution, after which carbon dioxide levels have risen from 285 to more than 400 parts
per million.[117] [118] (Scientists measure these gases in the atmosphere. To determine levels in earlier
periods, they assay carbon contained in tree rings and in bubbles trapped in ice cores.)
Carbon dioxide is a part of a complex process called the carbon cycle. All life forms derive from
carbon. Our bodies, our food, our clothes, and many of our building materials are carbon based. The
carbon cycle describes how carbon moves from one “reservoir” to another. The main reservoirs of carbon are living land organisms, fossil fuels, the oceans, and the atmosphere. Some reservoirs release carbon into the atmosphere; others act as carbon sinks, removing carbon dioxide from the atmosphere.
FIGURE 11.8 The Carbon Cycle
This diagram of the fast carbon cycle shows the movement of carbon between land, atmosphere, and oceans.
Yellow numbers are natural fluxes, and red are human contributions in gigatons of carbon per year. White numbers
indicate stored carbon. A balance between carbon storage and carbon release into the atmosphere holds
temperatures fairly steady.
Source: US Department of Energy, Biological and Environmental Research Information System. Climate placemat: energy-climate nexus.
http://earthobservatory.nasa.gov/Features/CarbonCycle/. 2008.
All organisms act as both sources and sinks for carbon. While living, plants, animals, and microorganisms tie up carbon in their cells. All organisms also break down carbon-based nutrients to create energy. This process, called cellular respiration, releases carbon dioxide. Every time you exhale, carbon dioxide leaves your body. Decomposition and combustion of organic matter also release carbon dioxide.
The burning of fossil fuels has generated a steadily increasing amount of atmospheric carbon dioxide.
Through photosynthesis, plants, ocean-dwelling plankton, algae, and some bacteria harness light
energy to convert water and carbon dioxide into carbohydrates and oxygen. Fast-growing trees are especially good at removing atmospheric carbon dioxide. Undisturbed biomass (e.g., old-growth forests),
soil, and sediments layering the ocean floor sequester carbon, meaning they act as reservoirs for carbon.
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Clear-cutting or burning a forest or generating energy from fossil fuels leads to a net increase in atmospheric carbon because an important carbon sink is lost and the stored carbon is released.
A longer-term cycle deposits atmospheric carbon in rocks such as limestone and
releases it when volcanoes erupt.[119] Carbon-containing rocks that undergo millions of FIGURE 11.9 Photosynthesis and
years of heat and pressure eventually become shale. In the same way, pressurized or- Carbon Capture
ganic material (dead plants and animals) becomes crude oil and natural gas. All are Plants take in water and atmospheric carbon
reservoirs of sequestered carbon. Additionally, the ocean absorbs carbon dioxide, dioxide and, using energy from sunlight, create
which dissolves and is eventually released again as a gas.
carbohydrates and oxygen, which is released
For hundreds of thousands of years, the carbon cycle remained fairly steady. A
massive phytoplankton bloom might remove extra carbon. The occasional volcanic into the air. The net effect is that atmospheric
eruption released large amounts carbon dioxide. Climate varied with such fluctuations carbon is removed and captured in the plant
in carbon dioxide levels; the temperature rose and fell in tandem with levels of carbon until the plant decomposes or burns.
dioxide.
In addition to carbon dioxide, other important greenhouse gases include water vapor, methane, nitrous oxide, and sulfur hexafluoride. Water vapor, the most abundant
of the greenhouse gases, is simply aerosolized water. Scientists are more concerned with
the other gases because human activities are largely responsible for their increase,
which means we have some ability to control their levels.
Methane, like carbon dioxide, is a colorless, odorless gas. The main constituent of
natural gas, methane can be combusted. Because decomposition of organic plant and
animal matter releases methane, swamps, marshes, and oceans are sources. Ruminants
(hoofed, cud-chewing animals such cattle, sheep, goats, bison, deer, and elk) release
methane from their intestinal tracts. Humans liberate this gas through mining for fossil
fuels and transporting natural gas.[120] As a greenhouse gas, methane is more than
twenty times more powerful than carbon dioxide.
Nitrous oxide is colorless and nonflammable. Oceans and rainforests release it.
Human sources include the use of fertilizers, the burning of fossil fuels, nylon production, and automobile catalytic converters.[121]
Sulfur hexafluoride is an extremely strong greenhouse gas and one that persists in
the atmosphere for more than a thousand years.[122] Electric power plants are the main
source.
As a result of population growth and economic development, humans have altered
the carbon cycle by increasing the concentration of greenhouse gases in the atmosphere. The principal human activities responsible for this change are the combustion
of fossil fuels, which emits carbon dioxide, and removing forests that would otherwise Source: At09kg. The scientific process of photosynthesis.
absorb carbon dioxide from the atmosphere. Since the Industrial Revolution, levels of http://commons.wikimedia.org/wiki/File:Photosynthesis.gif.
greenhouse gases and average temperatures have increased in tandem. From 1990 to 2011.
2013, the total warming effect from greenhouse gases added by humans to the Earth’s
atmosphere increased by 34 percent. In fact, the pace of climate change is accelerating.
Each of the last 3 decades has been successively warmer at the Earth’s surface than any preceding decade since 1850.[123]
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FIGURE 11.10 The Relationship between Greenhouse Gases and Global Temperatures
Rising Global Temperatures and CO2
Source: http://www.climatecentral.org/gallery/graphics/co2-and-rising-global-temperatures.
In 1988, the United Nations Environment Programme and the World Meteorological Association created the Intergovernmental Panel on Climate Change (IPCC) to provide a clear scientific view on climate change and its potential environmental and socio-economic impacts.[124] In 2014, the IPCC’s
Fifth Assessment Report concluded that human influence is 95 percent certain to have been the main
cause of the observed warming since the mid-20th century.[125] Those activities include fossil fuel combustion, which releases greenhouse gases into the atmosphere, as well as deforestation, which reduces
the ability of the planet to absorb carbon dioxide. While a few skeptics remain, NASA’s review of multiple studies published in peer-reviewed scientific journals indicates that 97 percent or more of actively
publishing climate scientists agree that climate-warming trends over the past century are very likely
due to human activities.[126]
2.1 Energy Production and Greenhouse Gases
nonrenewable energy
resources
Energy resources that natural
processes either do not
replenish or are replaced over
a long period of time.
As discussed in the preceding section, human activities are the main cause of the increased greenhouse
gas emissions since the mid-20th century. That’s because we rely primarily on nonrenewable energy
resources, those that natural processes don’t replenished or do so very slowly. Fossil fuels and nuclear
power are nonrenewable energy resources.
Combusion of fossil fuels to generate energy for electricity, heating and cooling, industrial processes, and transportation accounts for over 80 percent of greenhouse gas emissions. (Combustion is a
chemical reaction wherein atmospheric oxygen reacts with carbon and hydrogen in fuel, creating carbon dioxide, water vapor, and energy in the form of heat and light.
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FIGURE 11.11 Human-caused CO2 Emissions
Annual global anthropogenic (human-caused) carbon dioxide (CO2) emissions (gigatonne of CO2-equivalent per
year, GtCO2/yr) from fossil fuel combustion, cement production and flaring, and forestry and other land uses
(FOLU), 1750–2011. Cumulative emissions and their uncertainties are shown as bars and whiskers, respectively, on
the right-hand side.
Source: Intergovernmental Panel on Climate Change, 2014. Climate Change 2014: Synthesis Report. Figure 1.5, p. 45. Contribution of Working
Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A.
Meyer (eds.)]. http://www.ipcc.ch/pdf/assessment-report/ar5/syr/SYR_AR5_FINAL_full.pdf.
The energy-related carbon emissions result from the generation of electric power, principally with oil,
coal and natural gas; use of gasoline, diesel, and aviation fuels for transportation; and combustion of a
variety of fossil fuels for heating and cooling of residential and commercial buildings and in industrial
processes. The following chart shows the distribution of CO2 emissions among these energy sectors.
FIGURE 11.12 US Energy-Related CO2 Emissions
US energy-related carbon-dioxide emissions by sector, 2009.
Source: US Energy Information Administration. Available at: http://www.eia.gov/environment/emissions/ghg_report/ghg_overview.cfm.
Coal is the most carbon-intensive fossil fuel. Its use for generation of electric power has rapidly increased in recent years, particularly in developing countries such as China and India, reversing the
long-standing trend of gradual decarbonization (i.e., reducing the carbon intensity of energy) of the
world’s energy supply.[127]
The term carbon footprint refers to the amount of greenhouse gases, particularly carbon dioxide,
that a person, group, or product emits. Due to our appetite for fossil fuels, the United States is the
biggest producer of greenhouse gases. While Americans represent less than 5 percent of the world’s
population, we emit 14 percent of the carbon dioxide–a total of 16.1 tons per capita per year. Citizens
of the European Union, despite their high standard of living, produce 6.7 tons per capita per year–less
than half of the carbon dioxide that Americans do.[128]
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FIGURE 11.13 Energy-Related Carbon Dioxide Emissions by Country
Total Carbon Dioxide Emissions from the Consumption of Energy in 2011, by Country.
Source: Union of Concerned Scientists. http://www.ucsusa.org/global_warming/science_and_impacts/science/each-countrys-share-ofco2.html#.VYXc1kYuwgQ. Last Revised: November 18, 2014.
renewable energy
resources
Energy resources that natural
processes readily replace.
Other sources of energy are available that emit considerably fewer greenhouse gases than fossil fuels.
Nuclear energy, which is used to generate electricity, involves atomic fission (the splitting of atoms) to
create a heat-releasing chain reaction. Uranium is usually used in these reactions. Fission takes place in
nuclear reactors, which are designed with a number of safety mechanisms to keep the reaction from
getting out of control. Aside from the industrial processes required to mine, process, enrich, and transport uranium, nuclear energy does not generate carbon emissions.
The main disadvantage is the production of toxic radioactive waste material. A permanent solution to radioactive waste disposal has not been found. Moreover, while modern nuclear plants are designed to protect against radiation leaks, those measures can fail. For example, after a tsunami hit Japan
in 2011, a meltdown at the Fukushima Daiichi nuclear plant released radioactive materials into the environment. This and other nuclear plant failures have cast doubt on the safety of nuclear power facilities, causing several countries to announce that they plan to reduce their use of nuclear power.[129]
Renewable energy resources are readily replaced in nature. Examples include solar, wind, wave,
and geothermal power. Because they don’t produce greenhouse gases, they provide a solution to climate change. Furthermore, these resources are sustainable, meaning they allow people to maintain a
good-quality standard of living without compromising the health and energy needs of future
generations.
Solar power utilizes light or heat energy from sunlight. Solar thermal (heat) technologies take advantage of the sun’s warmth. A simple example is using the sun’s energy to warm water for household
use. More complicated technology concentrates solar energy to create steam, which operates a turbine.
Solar energy can also be converted directly into electricity using photovoltaic cells. In this case, sunlight
striking photosensitive materials produces an electric current.
Wind power indirectly stems from solar energy. When the sun heats the earth’s surface and the
oceans irregularly, cooler air (which is heavier) displaces warmer air, resulting in global and regional
wind currents. Sailors have long harnessed the wind for transportation; farmers developed windmills to
pump water and grind grain. Modern-day wind turbines are used to generate electricity.
Like wind, moving water is a type of kinetic energy made possible by the sun. For centuries, humans used running water to turn wheels to grind grain, lift water onto fields, and do other work. More
recently, hydroelectric power plants used the energy of water running down rivers or released from
dams to turn turbines that generate electricity. The energy of waves can be used in a similar fashion. In
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addition, the gravitational pull of the moon creates a steady source of tidal energy that can be harnessed
to generate electricity.
Geothermal power makes use of the warmer temperatures in the earth’s core. Rather than generating heat, the earth’s heat is moved. Warm air and water can be used to regulate heat in buildings. In
some areas, geothermal energy is relatively close to the surface, making it accessible to produce steam
to run a turbine.
Plants store the sun’s energy as chemical energy (carbohydrates). Living and recently living plants
form biomass, which can serve as a source of energy (biofuel). Woody plants (trees), plants high in sugar (corn), grasses, agricultural waste, and household garbage can all serve as biofuel. As long as the
plant grows relatively quickly and is sustainably harvested, biomass counts as a renewal source of
energy.
However, biomass combustion does release greenhouse gases and particulate matter. Furthermore,
the net energy efficiency of biomass can be reduced if the crops are grown with synthetic fertilizers and
planted, harvested, and transported using fuel-burning machines.[130]
Video Clip 17.2
This 2007 National Geographic video explains the basics of global warming, its causes, and its consequences.
Note that, since this video was made, average temperatures have climbed further.
View the video online at: http://www.youtube.com/embed/oJAbATJCugs?rel=0
2.2 Consequences of Climate Change
Climate change creates a wide range of risks to human health and well-being as well as the long-term
survival of many other species.
The most direct result is higher average temperatures on the land surface and in the oceans and
atmosphere. As shown in Figure 17.10, average temperatures have already risen by more than 2°F since
1880, at an average rate of 0.14°F per decade. The National Oceanic and Atmospheric Administration
(NOAA) reported that, in 2014, the combined land and ocean surface temperature was 1.24°F (0.69°C)
above the 20th century average, making the year the warmest since records began in 1880. Five months
set new records for warmth: May, June, August, September, and December.[131] While short-term variations are normal, global climate change underlies this marked and consistent alteration.
The most recent climate change assessment by the IPCC forecasts potential temperature increases
during the 21st century from 0.5°F (0.3°C) to 8.6°F (4.8°C), depending on how successfully the global
community can limit future greenhouse gas emissions. Additional variables include the extent to which
surface warming enhances other drivers of change, such as carbon and methane emissions from thawing permafrost, the melting of polar ice that would otherwise reflect incoming solar energy, and the loss
of carbon-absorbing vegetative cover from desertification.
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HEALTH NOW VERSION 2.0.4
FIGURE 11.14
Observed and projected changes in global average temperature under three emissions scenarios. The shaded areas
show the likely ranges while the lines show the central projections from a set of climate models. A wider range of
model types shows outcomes from 2 to 11.5°F. Changes are relative to the 1960-1979 average.
Source: United States Environmental Protection Agency. http://www.epa.gov/climatechange/science/future.html.
An important consequence of global warming is more extreme, unpredictable weather: some areas
will experience more heat waves and drought; other regions will see more precipitation and storms. In
a report released in the Bulletin of the American Meteorological Society (BAMS) and organized by
NOAA, 20 different groups of scientists determined that human influence on climate, particularly the
burning of fossil fuels, amplified certain temperature-related events in 2013, including 5 heat waves
across the globe.[132] However, the relationship between warming and extreme climate is itself unpredictable; the study did not find a link between human-induced warming and several extreme precipitation events that year.
Another study reported that human emissions are responsible for about 75 percent of especially
hot days and 18 percent of unusually heavy precipitation.[133] A 2015 report in the British medical
journal The Lancet concluded that exposure of people to extreme rainfall will more than quadruple and
the exposure to drought will triple over the next century.[134]
Hot, dry weather creates tinder for wildfires. In the United States in the summer of 2012, wildfires
scorched nearly 10 million acres.[135] Produce prices soared. As grasslands parched and the cost of hay
and grain soared, ranchers were forced to cull their herds. In the Southern Hemisphere in 2013, Australia and Tasmania suffered record-breaking heat, drought, and widespread fires.[136] A 2015 report
by the EPA estimated that global mitigation of climate change could prevent up to 7.9 million acres of
wildland fires in the United States alone and avoid up to $1.4 billion in firefighting costs in the year
2100.[137]
Warmer temperatures result in increased melting of polar ice. In the summer of 2012, the rate of
loss of Arctic sea ice was 50 percent higher than expected.[138] On February 25, 2015, Arctic sea ice extent appeared to have reached its earliest and lowest annual maximum extent ever recorded.[139] Increased melting of polar ice and glaciers leads to rising sea levels. Sea level elevation is compounded by
oceanic warming, because water expands as it warms.
Over the period 1901 to 2010, global mean sea level rose by 0.64 feet (0.19 meters). The IPCC
identifies several foreseeable scenarios for continued sea level rise over the next century, depending on
levels of greenhouse gas emissions and other factors, ranging from 0.85 feet (.25 meters) to 2.7 feet
(0.82 meters) by the year 2100.[140] The results of sea level rise include the loss of coastal wetlands and
mangroves, contamination of aquifers and agricultural land, larger storm surges, massive damage to
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property from coastal flooding, and displaced populations. If the Antarctic ice sheet begins to collapse—and there is some evidence that it is—more severe consequences may occur.[141]
A Disappearing Glacier
The Earth Vision Institute documented the dramatic retreat of the Mendenhall Glacier in Juneau, Alaska from
May 20, 2007 to March 13, 2014. To watch the time-lapse video, go to http://earthvisioninstitute.org/
share-this/mendenhall-glacier-alaska/.
Water shortages will become more widespread in a warming environment. A shift in rainfall patterns
will increase regional aridity. Declining winter snowfall and earlier spring thaws diminish the mountain snowpack. Since 1970, Northern Hemisphere snow cover has steadily declined.[142] Reduced
snowpack and earlier spring runoff means that, during the summer months, less water is available to
sustain rivers and streams. Diminished irrigation water lowers agricultural yields.
In addition, higher temperatures increase surface evaporation and transpiration (the water absorbed by plants and evaporated into the atmosphere). This factor, combined with changes in precipitation, will increase water shortages in areas such as the southwestern United States.[143] By 2050, the retreat of Himalayan glaciers is estimated to endanger the food security of 70 million people.[144]
Temperatures in permafrost (ground that remains frozen all year) have steadily risen. Animals and
plants adapted to the permafrost have lost habitats. In parts of Alaska, highways, airstrips, and buildings have begun to crack and crumble where the ground now thaws in summer.[145]
Unfortunately, loss of snow and ice amplifies global warming. Snow and ice reflect sunlight back
into space, which minimizes the absorption of heat by the planet. Particulate matter from dust storms,
fires, and urban pollution can travel thousands of miles on wind currents and settle on snowfields,
darkening them and causing them to absorb more of the sun’s energy. The heat increases melting. Bare
ground and unfrozen oceans absorb even more energy. Melting permafrost emits significant amounts
of methane and carbon dioxide. These positive feedback mechanisms lead to a vicious cycle of
warming.
Climate change will disrupt ecosystems and push many species toward extinction unless they can
adapt or migrate. The timing for seasonal events has already altered. Trees and plants flower and leaf
earlier in the spring, disrupting the timing of their availability to species that depend on them. Migration patterns for animals are shifting. Rising sea levels have jeopardized animals such as sea turtles that
breed on low-lying beaches and waterfowl that rely on marshes. Warming waterways and oceans disrupt riparian (river) and marine life. Ocean acidification and progressively lower oxygen levels will further jeopardize marine organisms. Coral reefs are particularly vulnerable. A loss of biodiversity resulting from the impairment of habitat for susceptible species will have long-term implications for the development of new food sources and medicines.
Some animal species can move to find more suitable habitats—the major exceptions being polar
animals such as penguins and polar bears who have simply run out of icy habitats and others whose
habitat has been constrained by human settlements. Since plants don’t migrate easily, many species
may become extinct before they can adapt. Pests such as the pine beetle have infested and heat-stressed
trees, blighting landscapes and creating dry tinder for forest fires.
The impacts on human populations are multiple, and poorer populations that lack resources, infrastructure, and essential services will be the most vulnerable. The rise of the oceans presents one of
the most serious threats to human societies from climate change. Millions of people living in areas subject to inundation and cyclical flooding will be displaced. This will exacerbate population pressures in
other parts of the world, with the attendant issues of political instability, food insecurity, and disease.
The increase in extreme weather events and long-term changes in precipitation patterns will also
affect public health, with risks ranging from localized storm damage to drought and flooding that
render land unsuitable for agriculture. Crop failures and loss of pastureland will increase food insecurity and outright famine. According to the World Bank, the world needs to produce at least 50 percent
more food to feed 9 billion people by 2050, but climate change could cut crop yields by more than 25
percent.[146] Compounding the problem is the decline in seafood due to overfishing and ocean warming, pollution, and acidification (from increased uptake of carbon dioxide). Malnutrition increases susceptibility to infections and other illnesses.
Climate change can indirectly increase risks of violent conflict, as in the case of food and water
shortages and resettlement of displaced populations. A recent extreme drought in Syria was attributed
to climate change and reported to be a factor in a violent uprising.[147]
A warmer world means more heat-related illness and death, particularly in the elderly and in
those with underlying heart and lung diseases.[148] Increased surface temperatures are already having
deadly consequences. From mid-April till the end of May, 2015, a heat wave in India killed nearly 2,200
people. India’s Minister of Science and Technology and Earth Sciences blamed the heat-related deaths
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squarely on climate change. In June 2015, more than 1,000 people died in a heat wave affecting
Pakistan's largest city, Karachi.[149] In the United States, the EPA warns that increases in summertime
temperature variability may increase the risk of heat-related death for the elderly and other vulnerable
populations, such as young children and people with cardiovascular and respiratory illnesses.[150] The
EPA has determined that climate change mitigation could prevent 12,000 deaths from heat-related illnesses in 49 major US cities in the year 2100.[151]
Infectious diseases will likely increase. Flooding can contaminate water with microbes, leading to
diarrheal illnesses such as cholera and typhoid. Flooding and excessive precipitation from storms allow
disease-causing fungi to proliferate. Water scarcity results in poorer sanitation and hygiene.[152]
Infectious diseases previously limited to the tropics have already spread into northern latitudes,
and that trend is expected to continue with a warming climate and related migration, malnutrition, and
poor sanitation and health care. For example, the mosquito-borne West Nile virus can adversely affect
the nervous system. The virus, which is common in Africa, West Asia, and the Middle East, was first
detected in the United States in 1999. Dengue fever, another mosquito-borne infectious disease, has
also spread.[153] Disease-carrying ticks have migrated northward. However, regions that become drier
could see reduced mosquito survival and a consequent decrease in mosquito-borne infections.
The earlier onset of spring and higher carbon dioxide levels (which will stimulate the growth of
plants such as ragweed) increase pollen counts, aggravating respiratory allergies and asthma.[154]
Video Clip 17.4
Climate Change Is Not a Partisan Issue
Unfortunately, global warming has become a polarizing political issue. However, the response to global
warming, a scientifically proven phenomenon, requires bipartisan cooperation. Watch “It’s Time to Find
Common Ground,” a speed-drawn video featuring the opinions of two scientists, one a Republican, the other a
Democrat.
View the video online at: http://www.youtube.com/v/TLg3B1Vi3XI
Source: Union of Concerned Scientists.
2.3 Responding to Climate Change
Carbon dioxide persists for a very long time in the atmosphere—as much as 40 percent of the carbon
dioxide emitted will remain for at least 1,000 years.[155] That means we can’t halt, much less reverse,
global warming in our lifetimes. However, we can immediately take action to mitigate the long-term
impacts on future generations. The only solution is a ...
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