Air quality surveillance: trends in selected urban areas.
D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000517:prevention & control*; D006262:Health; D006801:Humans; D013458:Sulfur Dioxide / Q000009:adverse effects; D014504:Urban Health; D014944:World Health Organization / Q000458:organization & administration
D000393:Air Pollutants; D013458:Sulfur Dioxide