In most European and North American cities, the concentrations of so2 and

Suspended Particulate Matter (SPM includes dust, fumes, mists and smoke — SO2

and troposphere ozone) have decreased substantially in recent years. However, in the US every second person has a car, about 170 million cars with the population of 280 million people; high concentration of industry and transportation turned the US into one of the biggest air polluters in the world, even though the number is decreasing. The US account for 26% of the total air pollution in the world.

The problem is not only in developed countries. In many developing countries,

rapid urbanization has resulted in increasing air pollution in many cities. WHO air quality guidelines are often not met and, in mega cities such as Beijing, Calcutta, Mexico City and Rio de Janeiro, high levels of Suspended Particulate Matter (SPM) prevail. The result of air and water pollution is chronic and infectious respiratory disease; water borne diseases; increased mortality rates, particularly among children; and premature deaths – the highest rate being among the poor. In Cairo, the leading polluted city, there are about 10.6 million people with respiratory disorder (SEI 1999). Air pollution is not only the cause of lung disease, but also has become the cause of heard attacks, birth defects and cancer.

In developing countries, transportation is not the main source of air pollution.

For example China and India together have about 600 million bicycles and much,

much fewer cars. If in the US every second person has a car, in China only every 79th person has a car, so the sources of pollution are different. People move from rural to urban areas to find better job and a better life, so many cities in China have a housing problem. Because the citycan’t offer decent housing, people live in small self-built shelters andusually heating and cooking is done by burning a very low quality coal, because it is the only cheap source of energy.

Beijing is one of the air polluted cities in the world and because of air pollution they have a desert problem.

All green plants around the city are dead and any efforts to plant new

trees and grass have had a miserable result. The geographical location plays not last role in the determination of air pollution of cities. For example, some cities in South America, which are located in high mountains have natural problem with free flow of air movement that removes polluted air. Besides, the low oxygen concentration in high mountain areas causes the partial burn of the fuel, which simply worsens the situation. For example Mexico city, the second largest city in the world, has a big problem with smog – dry, smoky fogs, which consist of carbon dioxide and nitrogen dioxide. Sometimes the smog stays for few days in the city

without any movement, causing enormous harm to the health of citizens of

Mexico city.

2.2.Water pollution

Water pollution problems vary in severity around the world, depending on

population densities, the types and amounts of industrial and agricultural development, and the number and efficiency of waste treatment systems that are used.

For a millennia, people have used water as a convenient sink into which to dump wastes. The pollution comes from many sources, including untreated sewage, chemical discharges, petroleum leaks and spills, and agricultural chemicals that are washed off or seep downward from farm fields. In one area after another, the amounts and types of waste discharged have outstripped nature's ability to break them down into less harmful elements. Pollution spoils large quantities of water which then cannot be used, or at best can be used for restricted purposes only. A growing number of regions face increasing water stresses because more people are both polluting and demanding more water for all uses from a renewable but finite resource. They are thus suffering from scarcities caused by failure to adapt to the amount of water that is regularly made available by rain and snowfall. Water demands are so high that a number of large rivers decrease in volume as they flow downstream, with the result that downstream users face shortages, and ecosystems suffer, both in the rivers and in adjacent coastal areas.

Many underground water resources, known as groundwater, are being drained

faster than nature can replenish them. Intensive and misuse of underground water leads to drainage of water recourses around the city, deserting the big areas beyond the cities boundaries. In some cases, groundwater depletion results in the land above aquifers sinking. Land subsidence caused by high water withdrawals has been recorded in many countries, including Mexico, the United States, Japan, China and Thailand, with the land sinking from 1 to 10 meters. South and Southeast Asia are facing severe water pollution problems.

Rivers such as the Yellow (China), Ganges (India), and Amu and Syr Darya (Central Asia) top the list of the world’s most polluted rivers. In cities in the developing countries of the region, most water bodies are now heavily polluted with domestic sewage, industrial effluents, chemicals and solid wastes. Most rivers in Nepal’s urban areas have been polluted and their waters are now unfit for human use, while drinking water in Katmandu is contaminated with coliform bacteria, iron, ammonia and other contaminants. There are estimates that in developing countries, which often lack the resources to build and maintain sewage treatment a system, 90 per cent of waste water is discharged without treatment. A UN study found that in Latin America, virtually all domestic sewage and industrial waste is discharged untreated into the nearest streams. In most areas, domestic sewage volumes are far higher than those of industrial discharges. There were similar findings from West Africa, where there were signs of shallow aquifers being contaminated by the seepage of human wastes.

2.3.Waste management

Some estimates show that New York wastes round 24’000 ton material everyday.

It contains metal, glass, plastics, paper, food and etc. It also includes dangerous substances like mercury from battery, phosphate from bulbs and other different type of toxic waste from paintings, detergents, home cleaners and etc. The sad fact is that wealthy city tends to use more energy and produce more waste than similar developing country’s cities. Developing countries trash about 2-3 times less waste than developed country. To satisfy an average costumer, for example, a company uses more packaging than it needed or more advertisements than it requires, which in other words mean more waste. Among the nations, the US produces the highest waste per person – 520 kg waste per person a year; in comparison Norway, Spain, Nederland – 200-300 kg, African cities – much less.

Depending on the country and its economic stand, there are different approaches to the waste management. Rich and developed countries or countries with scarce land supply use high tech processes to handle the waste. But on opposite side, poor and developing countries are still using the simple methods of waste discharge.