22.2 Effects of Air Pollution.
Lesson Objectives
- Describe the damage that is being done by smog.
- Discuss how acid rain is formed and the damage it does.
- Discus how chlorofluorocarbons destroy the ozone layer.
Introduction
People in developing countries often do not have laws to protect the air that they breathe.
The World Health Organization estimates that 22 million people die each year from compli-
cations due to air pollution. Even in the United States, more than 120 million Americans
live in areas where the air is considered unhealthy. This lesson looks at the human health
and environmental problems caused by different types of air pollution.
Smog
Allairpollutantscausesomedamagetolivingcreaturesandtheenvironment. Differenttypes
of pollutants cause different types of harm. Particulates reduce visibility. For example, in
the western United States, people can now ordinarily see only about 100 to 150 kilometers
(60 to 90 miles), which is one-half to two-thirds the natural (pre-pollution) range on a clear
day. In the East, visibility is worse. People can only see about 40 to 60 kilometers (25-35
miles), which is one-fifth the distance they could see without any air pollution.
Particulates reduce the amount of sunshine that reaches the ground. Since plants also
receive less sunlight, there may be less photosynthesis. Particulates also form the nucleus
for raindrops, snowflakes or other forms of precipitation. An increase in particles in the
air seems to increase the number of raindrops, but often decreases their size. By reducing
sunshine, particulates can also alter air temperature. In the three days after the terrorists
attacks on September 11, 2001, jet airplanes did not fly over the United States. Without the
gases from jet contrails blocking sunlight, air temperature increased 1°C (1.8°F) across the
U.S (Figure22.6). Imagine how much all of the sources of particulates combine to reduce
temperatures.
Ozone damages some plants. Since ozone effects accumulate, plants that live a long time
show the most damage. Some species of trees appear to be the most susceptible. If a forest
contains ozone-sensitive trees, they may die out and be replaced by species that are not as
easily harmed. This can change an entire ecosystem, since animals and plants may not be
able to survive without the habitats created by the native trees.
Some crop plants show ozone damage. When exposed to ozone, spinach leaves become