Air Pollution - Environmental Science - page 350

Air Pollution in the Past: The Bad Old Days

Modern civiliza-
tion did not invent
air pollution. It
probably began
when humans dis-
covered fire, began
to burn wood in
poorly ventilated caves for warmth
and cooking, and inhaled unhealthy
smoke and soot.
During the Middle Ages, a haze
of wood smoke hung over densely
packed urban areas. The Industrial
Revolution brought even worse air
pollution as coal was burned to
power factories and heat homes.
By the 1850s, London had be-
come famous for its “pea soup”
fog—a mixture of coal smoke and
fog that blanketed the city. In 1880,
a prolonged coal fog killed an esti-
mated 2,200 people. Another in 1911
killed more than 1,100 Londoners.
The authors of a report on this dis-
aster coined the word smog to de-
scribe the deadly mixture of smoke
and fog that enveloped the city.
In 1952, an even worse yellow
fog lasted for 5 days and killed
4,000-12,000 Londoners, prompting
Parliament to pass the Clean Air Act
of 1956. Air pollution disasters in
1956, 1957, and 1962 killed 2,500
more people. Because of strong air
pollution laws, London's air today

is much cleaner, and “pea soup”
fogs are a thing of the past. Instead,
the major threat comes from air pol-
lutants emitted by motor vehicles.
The Industrial Revolution, pow-
ered by coal-burning factories and
homes, brought air pollution to the
United States. Large industrial cities
such as Pittsburgh, Pennsylvania,
and St. Louis, Missouri, were notori-
ous for their smoky air. By the 1940s,
the air over some cities was so pol-
luted that people had to use their au-
tomobile headlights during the day.
The first documented air pollu-
tion disaster in the United States
occurred on October 29, 1948, at the
small industrial town of Donora in
Pennsylvania's Monongahela River
Valley. Pollutants from the area's
coal-burning industries became
trapped in a dense fog that stag-
nated over the valley for 5 days.
About 6,000 of the town's 14,000 in-
habitants became sick, and 22 of
them died. This killer fog resulted
from a combination of mountain-
ous terrain surrounding the valley
and weather conditions that
trapped and concentrated deadly
pollutants emitted by the commu-
nity's steel mill, zinc smelter, and
sulfuric acid plant.
In 1963, high concentrations of
air pollutants accumulated in the

air over New York City, killing
about 300 people and injuring thou-
sands. Other episodes in New York,
Los Angeles, and other large cities
in the 1960s resulted in much
stronger air pollution control pro-
grams in the 1970s.
In 1952, Oregon became the
first state to pass a law controlling
air pollution. The U.S. Congress
passed the original version of the
Clean Air Act in 1963. It did not
have much effect until a stronger
version was enacted in 1970 and the
Environmental Protection Agency
(EPA) was created and empowered
to set and enforce national air pol-
lution standards. Even stricter emis-
sion standards were imposed by
amendments to the Clean Air Act in
1977 and 1990. Mostly as a result of
these laws and actions by states and
local areas, air quality has dramati-
cally improved throughout the
United States.

SCIENCE
SPOTLIGHT

Critical Thinking
Explain why you agree or disagree
with the following statement: “Air
pollution in the United States is no
longer a major concern because of
the significant progress made in
reducing outdoor air pollution
since 1970.”

produce photochemical smog—a mixture of ozone, ni-
tric acid, aldehydes, peroxyacyl nitrates (PANs), and
other secondary pollutants.
Hotter days lead to higher levels of ozone and
other components of smog. As traffic increases on a
sunny day, photochemical smog (dominated by O 3 )
usually builds up to peak levels by early afternoon, ir-
ritating people's eyes and respiratory tracts.
All modern cities suffer from some photochemical
smog, but it is much more common in cities with
sunny, warm, dry climates and lots of motor vehi-
cles—for example, Los Angeles, Denver, and Salt Lake
City in the United States; Sydney, Australia; São
Paulo, Brazil; Buenos Aires, Argentina; and Mexico
City, Mexico (Figure 15-4). According to a 1999 study,
if 400 million people in China drive gasoline-powered
cars by 2050 as projected, the resulting photochemical

smog could cover the entire western Pacific with

ozone, extending to the United States.

See how photochemical smog forms and how it affects us at
Environmental ScienceNow.

Science: Industrial Smog
Industrial smog is a mixture of sulfur dioxide,
droplets of sulfuric acid, and suspended solid
particles emitted by burning coal and oil.
Fifty years ago, cities such as London, England, and
Chicago and Pittsburgh in the United States burned
large amounts of coal and heavy oil (which contain
sulfur impurities) in power plants and factories and
for heating homes and cooking food. During winter,