Visualizing Environmental Science

Effects of Air Pollution 201

breathlessness and wheezy breathing. Chronic bronchitis is

a disease in which the air passages (bronchi) of the lungs

become permanently inflamed, causing breathlessness

and chronic coughing.

Urban Air Pollution

Air pollution in urban areas is often called smog. The term

smog was coined at the beginning of the 20th century for

the smoky fog prevalent in London because of coal com-

bustion. Traditional London-type smog—that is, smoke pol-

lution—is sometimes called industrial smog. The principal

pollutants in industrial smog are sulfur oxides and particu-

late matter. The worst episodes of industrial smog typically

occur during winter months, when combustion of house-

hold fuel such as heating oil or coal is high. Because of air

quality laws and pollution-control devices, industrial smog

is generally not a significant problem in highly developed

countries today, but it can be severe in developing countries.

Another important type of smog is photochemical

smog. First noted in Los Angeles in the 1940s, photo-

chemical smog is generally worst

during the summer months. Both

nitrogen oxides and hydrocar-

bons are involved in its formation.

A photochemical reaction occurs

among nitrogen oxides, largely

from automobile exhaust; volatile

1. Relate, in general terms, the adverse health
   effects of air pollutants.


2. Describe industrial smog, photochemical smog,
   temperature inversions, urban heat islands, and
   dust domes.

A

ir pollution injures organisms, reduces visibil-
ity, and attacks and corrodes materials such
as metals, plastics, rubber, and fabrics. Air
pollutants harm the respiratory tracts of ani-
mals, including humans, and can worsen existing medical
conditions, such as chronic lung disease, pneumonia, and
cardiovascular problems. Most forms of air pollution re-
duce the overall productivity of crop plants. Air pollution
is involved in acid deposition, global warming, and strato-
spheric ozone depletion (all discussed in Chapter 9).

Air Pollution and Human Health

Generally speaking, exposure to low levels of pollutants
leads to irritation of the eyes and inflammation of the
respiratory tract (Table 8.1). Many air pollutants also
suppress the immune system, increasing susceptibility to
infection. In addition, exposure to air pollution during
respiratory illnesses may result in the development later
in life of chronic respiratory diseases, such as emphysema
and chronic bronchitis. In emphysema, the air sacs (alveoli)
in the lungs become irreversibly distended, causing

Effects of Air Pollution

LEARNING OBJECTIVES

photochemical

smog A brownish-

orange haze formed

by chemical reactions

involving sunlight,

nitrogen oxides, and

hydrocarbons.

(EALTHEFFECTSOFSEVERALMAJORAIRPOLLUTANTS sTable 8.1

Pollutant Source Effects

Particulate matter Industries, motor vehicles Aggravates respiratory illnesses; long-term exposure may cause chronic

conditions such as bronchitis

Sulfur oxides Electric power plants, Irritate respiratory tract; same effects as particulates

industries

Nitrogen oxides Motor vehicles, industries, Irritate respiratory tract; aggravate respiratory conditions such as asthma

heavily fertilized farmland and chronic bronchitis

Carbon monoxide Motor vehicles, industries Reduces blood’s ability to transport oxygen; causes headache and fatigue at

low levels; mental impairment or death at high levels

Ozone Formed in atmosphere Irritates eyes; irritates respiratory tract; produces chest discomfort;

(secondary air pollutant) aggravates respiratory conditions such as asthma and chronic bronchitis