Idea Transcript
CHAPTER SIX
INTRODUCTION The composition of the atmosphere has been gradually changing over the past millions of years, it is only during the last two to three hundred years, since the beginning of the industrial revolution in Europe and North America, however, that man has begun to affect this change. The process has accelerated over the past 50 years as more countries have also embarked on rapid economic development. This chapter reviews some of the important trends dealing with local air quality and regional concerns such as haze and acid rain, as well as the regional contributions to, and implications of, global climate change and stratospheric ozone depletion. The policies and response strategies that are being formulated or implemented in the Asian and Pacific Region to address these concerns are also discussed.
AIR POLLUTION Types of Air Pollution-Indoor and Outdoor While this chapter deals with the issues of pollution to the atmosphere and climate locally, regionally and globally, it is also important to note the significant hazards posed by indoor air pollution. For example, where a large part of the population still depends on traditional biomass fuels for cooking and heating, indoor air pollution may be a larger health hazard than outdoor pollution. The burning of such fuels in a confined space usually produces high levels of smoke and other pollutants. Estimates (for the Asian and Pacific Region) indicate that the concentrations of particulates may exceed WHO guidelines by factors of ten or more (WHO 1997) in many households, particularly in South Asia. The data in Table 6.1 suggest that tens of millions of people in Asia and the Pacific are being exposed to indoor levels of air pollution comparable to the notorious outdoor levels during the “London smog” of 1952, in which about 4 000 deaths occurred due to respiratory diseases.
The number of vehicles in Asian cities has been growing exponentially over the last two decades. In Delhi and Manila, for example, they have been doubling every 7 years (ADB 1999). A large portion of vehicles in most Asian cities use diesel fuel, and contribute greatly to the emissions of particulates, especially those that are less than 10 microns in size and are respirable (PM10). Several countries, including India, Pakistan, and the Philippines, still subsidize diesel fuels. In many countries, transportation fuels contain lead and high amounts of sulphur and use older engine designs that emit more pollution than modern ones. Since vehicles in developing countries are typically kept for longer periods than in the industrialized countries, they continue to contribute a substantial share of the air pollution in urban areas as their engines become increasingly less efficient. The situation is compounded by the region’s reliance on motor cycles and three-wheel vehicles which frequently use two stroke engines and consequently produce up to 10 times more hydrocarbons than normal 4-stroke engines (ADB 1999).
A.
B.
Sources of Air Pollution The combustion of fossil fuels (coal, oil, and natural gas) is the principal source of air pollution in all urban areas, along with the burning of biomass such as firewood, agricultural wastes and animal wastes in rural areas and some cities. Most of the combustion of fossil fuels takes place in industries, homes, for transportation, and for the generation of electricity. However, in the vast majority of Asian cities, transportation is the largest source of air pollution.
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Table 6.1
Indoor Concentrations of Particulate Matter due to Biomass Combustion
Location
Number of Studies
PR China Pacific South Asia
Source:
C.
Duration
Concentration
8
Various
2 600-2 900
All
2
12 hours
1 300-5 200
All
Cooking Cooking period Non-cooking 24 hours Various Urban infants, 24th
630-820 850-4 400
All