BY 2020, more than 30 million people living in just four Asian cities could be reeling under sulphur pollution levels far in excess of WHO safety limits. But efforts to cut sulphur emissions could cost an astounding $87 billion a year.
Asia is urbanising rapidly. By 2025, approximately 3 billion people are expected to be living in urban areas, fuelling demand for power plants, cars, domestic heating, and small-scale industries 鈥� all of which spew sulphur dioxide into the atmosphere.
To determine current levels of sulphur pollution, Gregory Carmichael at the University of Iowa鈥檚 Center for Global and Regional Environmental Research and his colleagues drew upon an extensive database called the Regional Air Pollution Integration and Simulation project, which holds data on fuel and energy usage, power plants and transportation for about 100 Asian cities, prefectures and states. They used it to calculate the amount of sulphur dioxide the regions emitted from 1975 to 2000 and compared it with emissions from all sources, including volcanoes and shipping.
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They found that pollution from cities in the Indian subcontinent and South-East Asia nearly quadrupled in 25 years. Chinese cities were even more polluted.
To study the likely impact of continued urbanisation, the team modelled two future scenarios. One, called 鈥淏usiness as Usual鈥�, assumed that emissions and fuel controls remain unchanged. The other, called the 鈥淢aximum Feasible SO2 Emission Control鈥� (MAXF), assumed a realistic degree of implementation of a raft of pollution controls. These included using low-sulphur fuels for transportation, and flue gas desulphurisation for power plants. Current pollution controls in Asia run the gamut from modern technology in newer power plants to plants that don鈥檛 even wash coal to remove sulphur before using it.
The 鈥淏usiness as Usual鈥� model predicts that by 2020 sulphur pollution levels will have tripled in and around cities on the Indian subcontinent, including Karachi and Kolkata. The researchers then zoomed in on four cities, Shanghai, Chongqing in eastern China, Seoul in South Korea and Mumbai (formerly Bombay). They found that peak SO2 concentrations would reach 248 micrograms per cubic metre in Shanghai, 288 in Chongqing, 82 in Seoul, and 226 in Mumbai 鈥� all way over the WHO maximum safe limit of 60 micrograms per cubic metre in residential areas (Atmospheric Environment, vol 37, p 11). This, says Carmichael, puts over 30 million people at risk of respiratory and cardiac problems in these cities alone. 鈥淚t paints a very, very bleak scenario.鈥�
Fortunately, the MAXF model shows that most cities can reduce sulphur pollution to less than 60 per cent of 2000 levels. While achieving MAXF levels would cost Asia $87 billion a year, a clampdown could be worth the money. The World Bank estimates that sulphur pollution already costs China alone nearly $45 billion each year in lost productivity, health care and damage to forests and crops.
Veerabhadran Ramanathan, a pollution expert at the University of California, San Diego, says, 鈥淏oth as scientists and policy makers, we should definitely pay heed to this study.鈥�