Physical problems of cities include substandard housing, pollution, and traffic congestion. The term substandard housing refers to poorly constructed, run-down, unsanitary, or overcrowded dwellings. In developing nations, millions of people live in crude shacks or other dwellings that barely provide shelter. The people of advanced nations are better off. Even so, some housing in advanced nations is also substandard. Many governments have set up programs to improve housing for needy families. However, population growth, lack of funds, the high cost of construction, and other factors continue to cause a worldwide housing crisis.

Motor vehicles, factories, and other sources pollute the air with fumes that endanger the health of the people in cities. Urban wastes pollute waterways. City residents and industries produce extraordinary amounts of refuse. A government might want to end pollution by eliminating sources of contamination. But the government would need to close factories and prohibit almost all automobiles to do so, thus crippling the economy and inconveniencing the people.

Instead, citizens, governments, industry, scientists, and business people must work together to gradually reduce pollution. For example, most cities have introduced recycling programs, which cut down on refuse and the space needed to store it. Residents separate recyclable products from garbage, and city governments provide drop-off sites or pick up the products from homes.

Excerpt from the "City" article, The World Book Encyclopedia © 1999