| Air Pollution in Mega cities |
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| Thursday, 14 February 2008 | |
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The freshness of the air in one's environment has a most fundamental and direct impact on the quality and length of one's life. Air is more a necessity of life than either food or water. Imagine you live in a city where a gray-brown noxious haze of smog permeates the streets in your district. Imagine that these streets are filled with jam-packed traffic, a slow moving assembly of automobiles which blow out unhealthy exhaust fumes of carbon monoxide and other harmful chemicals. You cover your nose and mouth with a handkerchief to avoid excess exposure to dust and chemical particulates in the air. The air is not pleasant to inhale in deeply, and it gives you breathing trouble, making you co ugh and wheeze. In addition, your eyes water, your nose runs, and you have headaches and irritated eyes regularly when you are outdoors. As you walk on a street in this particular city on a weekday afternoon, a jogger passes by you wearing a face mask, an d you observe children playing in a nearby school, inside a giant glass bubble to shield them from the city air. 
Over one million of the 18 million Mexico City residents suffer permanent breathing difficulties, headaches, coughs and eye irritations. New studies suggest that children living in neighborhoods with the worst air could suffer permanent alterations to cel ls in their nose and throat linings which could lead to cancer later in life. In 1974 the Global Environment Monitoring System (GEMS) was created by the World Health Organization and The United Nations Environment Programme (UNEP) to monitor air pollution in large cities of the world. Indeed, urban air pollution could become a public health and environmental problem of crisis proportion early in the next century, if this is not already the case. The network monitors levels of suspended particulate matter concentration, lead, carbon monoxide, nitrogen dioxide, sulfur dioxide, and oz one in the air. Although air pollution is only one of the many environmental hazards in urban centers of the world, along with water contamination, hazardous wastes, overcrowding, congestion, and so on, it is a unique problem as it affects every resident, it is seen by e very resident, and is caused by nearly every resident. Of foremost concern in monitoring air quality in large cities is the health and well-being of urban residents. The concentration of ambient air pollutants in many of the cities are high enough to cause increased mortality, disease prevalence, deficits in pulmonary function and cardiovascular and neurobehavioral effects. Indoor sources of air pollution, such as cooking fires and tobacco smoking, have contributed toward general human exposure as well. Air pollution is seriously damaging also to the material resources of cities, such as buildings and various works of art. Its impact on vegetation is also of concern. The most recent WHO/UNEP report on air quality in 1992 focused on 20 of the 24 megacities of the world. Megacities were defined for the purpose of the study as urban agglomerations with current or projected populations of 10 million or more by the year 20 00. The urban areas chosen include cities in all parts of the world _ two in North America (Los Angeles, New York), four in Central and South America (Rio de Janeiro, Sao Paulo, Buenos Aires, Mexico City), one in Africa (Cairo), 11 in Asia (Bangkok, Beiji ng, Bombay, Calcutta, Delhi, Jakarta, Karachi, Manila, Seoul, Shanghai, Tokyo) and two in Europe (London, Moscow). The UN estimates that by 2000 there will be 59 "supercities" having over five million population and many of these will reach megacity status by the next century. The study of air pollution problems in the 20 megacities is intended to guide efforts to so lve and prevent some of these problems from occurring in emerging megacities. Preventing pollution problems before they occur is usually the most cost-effective method for dealing with air pollution. The first observation made by the report is that air pollution is widespread across the megacities and is often most severe in cities in developing countries. In developed countries, such as in the US or UK, health norms are exceeded to a much lesser degree. The worst group of the megacities in terms of air pollution consists of Beijing, Cairo, Jakarta, Los Angeles, Mexico City, Moscow and Sao Paulo. In these cities three or more of the five substances listed earlier exceed WHO guidelines by more than a f actor or two. Five of these seven cities, it might be noted, are present in the Pacific basin. The suspended particulate concentration of the air has a significant impact on one's health. Recent US studies show mortality correlation with SPM at low levels of SPM. Hence there is the concern that more serious SPM-related mortality exists at similar S PM levels in developing countries where the delivery of medical care is much less proficient than in the US. The effects of high SPM as often difficulties with breathing as well as more serious respiratory problems. There are only three megacities in which suspended particulate matter concentration is by-and-large within WHO prescribed limits: Tokyo, New York, and London. These are the three most developed megacities in the world. Concentrations of suspended particulate matter indeed present serious problems in the Pacific Basin. Bus drivers have the highest prevalence of chronic respiratory problems in the Philippines in the Pacific Rim. In Manila, Philippines, the Asian Developme nt Bank (AsDB) found levels of suspended particulate matter in the air to be 200-400 per cent above guideline levels. Air-borne lead is an important air pollutant where leaded petrol is still sold. In high concentrations it is known to impair liver and kidney functions and is associated with reduced mental development of infants and children. Although lead is emitted b y vehicles as small particles, it can agglomerate into large particles that circulate through wind and traffic. For the cities surveyed, high levels of lead were recorded in the air of Cairo and Karachi and, to a lesser extent, in Bangkok, Jakarta, Manila and Mexico city. In most of the other megacities lead levels are low or have been completely eliminated. Lead is now banned in petrol in countries like the US, Japan, and Sweden. In most EU countries the permissible amount of lead in petrol is highly limited. In other countries such as Africa, Latin America, and much of Asia, however, there are fewer restrictions and the situation is much different. Lead levels in African cities like Cairo, Cape Town and Lagos, or are up to ten times those of the typical Europ ean cities. This is an unfortunate fact, given the fact that the US Public Health Service maintains that concentrations of lead in the blood of children over 100 um per liter causes "measurable and irreversible" damages, with a 2 to 4-point average IQ deficit for eac h increase of 100 to 150 um per liter in blood lead. Given this, imagine the extreme hazards faced by children in Bangkok, who in the 1990 study had typical blood-lead levels of 400 um per liter. A downward trend for sulfur dioxide is evident in Asian and Latin American countries such as Bangkok, Bombay, Sao Paulo and Seoul. This is due to the fact that coal and high sulfur oil have been replaced by cleaner fuels such as natural gas which contains less ash and less sulfur. Along with this changeover have come reductions in air pollution with regard to sulfur dioxide in many megacities of the world. Motor vehicle traffic is a major source of air pollution in the megacities. In half of them it is the single most important source. It is a major source of four of the six major air pollutants -- carbon monoxide, nitrogen oxides, hydrocarbons and lead - and contributes to the SPM concentration as well. Within the next twenty to thirty years, the number of vehicles in the world, a number which has grown tenfold since 1950, is likely to double from its present total of 630 million vehicles, according to the WHO/UNEP study. As cities expand into megacities , more people will drive more vehicles greater distances and for longer times. In the absence of controls, the automotive emissions will likewise increase. Even in cities where a substantial proportion of the motor vehicle fleet is (much cleaner) diesel-powered there are additional problems of black smoke and greater particulate emissions. The need for automotive emissions controls is paramount, considering the already high concentrations of air pollutants, the rapid increase in motor vehicle traffic, and the long time it takes for controls to take effect. The GEMS study concluded that from a review of the trends in air quality in different cities it is quite evident that "history repeats itself." The experience of the current megacities in the developed countries is now being repeated in the developing cou ntries. Based on the study, WHO/UNEP (1992) made several recommendations for developing countries to follow to address the problems of urbanization and air pollution: 1) Air quality management should be implemented urgently. Such efforts are needed in well over half of the megacities studied 2) More attention should be given to short-term, realistic approaches to begin to reduce some of the air pollution. Steps which can be taken include energy conservation, institution of motor vehicle inspection programs and phasing out lead in petrol. Pro motion of the use of mass transit and finding alternatives to open burning of refuse provide some other opportunities for reducing air pollution in the near term 3) In the longer term, preventive measures must be incorporated in new industrial and urban developments. Proper urban and transportation planning can achieve significant improvements in air quality, as can the introduction of clean modern technology.
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| Last Updated ( Thursday, 03 July 2008 ) |
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