If current trends continue, auto emissions are bound to rise. The number of vehicles on Beijing's roads quadrupled between 1986 and 1996 and 177,000 new vehicles hit the city's jammed streets between January and November last year. For at least five months last year, the air pollution index was reported at ''level four'' - severe enough to endanger heart and lung patients and to cause healthy people to develop symptoms such as coughing and sore throats. Last spring, the state-run news media began publishing weekly air quality reports. As the air grew progressively dirtier throughout the autumn, those reports vanished or were buried in tiny columns in local newspapers.
Weather is partly to blame.
Last year was unusually warm and the winds that usually sweep the skies clear in spring and autumn were unusually calm. Frequent temperature inversions trapped smog over the city, which is ringed on three sides by mountains. Only on windy days do Beijingers see the purple mountain ranges to the west. Most nights, the skies are rosy-gray. City lights glow dimly through a thick haze.