of fuels in power plants to generate electricity, in factories to make machinery run, in stoves
and furnaces for heating, in various modes of transportation, and in waste facilities to burn
waste. Even before the use of fossil fuels since the Industrial Revolution, wood was burned
for heat and cooking in fireplaces and campfires, and vegetation was burned for agriculture
and land management.
In addition to the burning of fossil fuels, other sources of human-caused (anthropogenic)
air pollution are agriculture, such as cattle ranching, fertilizers, herbicides and pesticides,
and erosion; industry, such as production of solvents, plastics, refrigerants, and aerosols;
nuclear power and defense; landfills; mining; and biological warfare.
Environmental Effects of Outdoor Air Pollution
Manyoutdoorairpollutantsmayimpairthehealthofplantsandanimals(includinghumans).
There are many specific problems caused by the burning of fossil fuels. For example, sulfur
oxides from coal-fired power plants and nitrogen oxides from motor vehicle exhaust cause
acid rain(Figure25.5) (precipitation or deposits with a low pH). This has adverse effects
on forests, freshwater habitats, and soils, killing insects and aquatic life.
Figure 25.5: A forest in the Jizera Mountains of the Czech Republic shows effects attributed
to acid rain. At higher altitudes, effects of acid rain on soils combines with increased pre-
cipitation and fog to directly affect foliage. ( 9 )
Global warming(an increase in the earth’s temperature) is thought to be caused mostly
by the increase ofgreenhouse gases(water vapor, carbon dioxide, methane, ozone, chlo-
rofluorocarbons (CFCs), nitrous oxide, hydrofluorocarbons, and perfluorocarbons) via the
greenhouse effect(the atmosphere’s trapping of heat energy radiated from the Earth’s
surface).