The Pearl River Delta (PRD) is an area of rapid development in South China . In addition to the shared air space of Guangdong , Zhuhai and Hong Kong , the inter-connectedness of the region is rapidly increasing with the proposed new network of roads and bridges designed to span the delta.
From time series studies the largest average excess risks per 10 µg/m 3 of pollutant with current ambient levels of pollution are 3.3% for primary care respiratory consultations (PM 10); 1.36% for all causes mortality (SO 2), (0.5% for traffic related pollution (NO 2)), and 3.0% for hospital admissions (NO 2), with the highest values in cool seasons. In Hong Kong at the end of the 1980’s, annual average levels (µg/m 3) of the four criteria pollutants were 18.5 (O 3), 44.2 (SO 2), 54.7 (NO 2) and 59.8 (PM 10). Childhood (8-10y) respiratory symptoms and doctor consultations showed excess risks of 35% between higher and lower polluted districts. On 1 st July 1990 the Environmental Protection Department introduced legislation restricting the sulfur content of fuel to 0.5% by weight. SO 2 levels fell by 80% in the most polluted areas and by 53% over the whole territory (approx 1100 km 2). There were also sharp reductions in annual ambient concentrations of Vanadium and Nickel. There were no sustained reductions in PM 10, NO 2, and O 3. The immediate effects of this modest restriction in fuel sulfur included large reductions in the risks of bronchial hyper-responsiveness and bronchitic symptoms in primary school children. In the first cool season after the intervention the expected seasonal mortality peak was markedly attenuated. The acute reduction in deaths was in middle life and older people (mid 40y+) and specific for cardiopulmonary disease, but not other indicator conditions such as cancer or gastrointestinal conditions. Over the five years post-intervention we estimated an average reduction in all causes mortality of 2.2% per year equivalent to 600 deaths per year, or 10,000 person-years of life gained. This analysis demonstrates the independent effect of one criteria pollutant and the large health gains from even modest air quality interventions.
Further reductions in fuel sulfur down to 0.005% have been made since 1990 but trends in average annual concentrations of PM 10, NO 2, and O 3 continued to show an increase in the 1990’s. The introduction of cleaner fuels (LPG) and engines and other technology in Hong Kong since 2000 has mitigated ambient and roadside levels of PM 10 and NO 2, but mean concentrations remain high and future trends are uncertain. Recently in the PRD the consumption of Bunker C fuel (which is illegal in Hong Kong ), rich in sulfur and metals, has increased sharply in response to economic upturn and energy shortages. The effects are reflected in an increase in low visibility days throughout the Delta and are now likely to negate some of the health and economic gains from local restrictions in fuel sulfur. Continuing increases in vehicular traffic in the PRD and demands for energy will probably outweigh slower moves to cleaner fuels, engines and enforcement.
Epidemiological research on health effects, health care utilization, linked to economic appraisal, are essential elements of strategies to promote clean air policies in the Asia Pacific region.
References
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