Urban air pollution has three main components: industrial and vehicle exhausts and domestic heating. The concentrations of air pollutants depend not only on the quantities emitted by also on the ability of the atmosphere either to absorb or disperse them. That is why in each individual case, so much hinges on meteorological and topographic factors. The actual siting of settlements is also of great importance. Clearly, there is a difference between a housing complex situated in a "green belt" away from industrial locations or busy motorways, and one surrounded by heavy industry enterprises and waste disposal sites. Energy generation adds considerably to the overall levels of urban air pollution, its emission greatly contributing to the intricate photochemical conversions leading both to smog and acid rain.
Many environmental problems reinforce one another in small, densely-populated areas. Air pollution, garbage, hazardous wastes, noise and water contamination turn these areas into environmental hot spots. Children are the most vulnerable to the inevitable health risks. Some 30-60 per cent of the urban population in low-income countries still lack adequate housing with sanitary facilities, drainage systems and piping for clean water. Continuing urbanization and industrialization, combined with a lack of resources and expertise, are increasing the severity of the problem.
[Developing countries] Spectacular economic growth in Southeast Asia has led to sharp increases in consumption of energy and consequently in emissions of sulphur dioxide and other pollutants. Energy consumption has been doubling every 12 years. Local air pollution problems are already severe: 12 of the 15 most polluted cities of the world (i.e. highest levels of particulate matter) are in Asia. Less than one percent of 500 Chinese cities have clean air. Respiratory disease is the leading cause of death in China. Airborne particulate matter increased five-fold in some districts of Mexico City during the decade of the 1980s. Because of the air pollution, it is compulsory for employees at the Japanese Chamber of Commerce in Mexico City to spend 45 days a year on vacations outside the city. WHO estimates that in Latin America alone, more than 24,000 lives are lost every year through permanent exposure to high air pollution in cities.
[Former socialist countries] Communist development has favoured heavy industry like steel and chemicals, which produce copious toxic waste. Lacking price signals, the planned economies became highly inefficient users of energy, other source of pollution. The main fuel is also the dirtiest: coal, especially brown coal or lignite. Besides, there were or are no pressure from the public on the planners to heed the consequences of pollution. The industrial fallout levels in eastern Europe are 10 to 20 times greater than in western Europe.
In 1992, there were 84 towns in Russia where the air pollution was more than 10 times the permissible levels. Moscow was one of them.