Wen Shi, a 51-year-old worker at a carwash in the eastern suburbs of Chengdu, the capital of Sichuan Province, felt exhausted yesterday.

"A long queue of over 100 cars was waiting for us to give them a thorough cleaning. But the station only has six staff," he said.

Almost all the cars were covered with gray and black dust. Even after being cleaned, a car would be covered with a thin layer of dust five minutes after it left the carwash.

Zhao Wu, a 36-year-old taxi driver who was waiting to have his car washed, said that a heavy rain that fell on the city early Wednesday morning was to blame.

After the rain, as Zhao was about to start work, he noticed his recently washed car was covered with a gray, slushy substance.

Looking around, he found all the other seven cars parked in the courtyard looked the same as if they had just come back from a desert, he said. Zhao called the city's environmental protection bureau, which said that many local residents had reported the same experience.

The environmental protection bureau staff rushed to the area, and found that trees, flowers and buildings in many streets were covered with gray, black slurry.

Ruling out the possibility of acid rain or a sandstorm, the bureau suspected that the nearby Jialing Thermal Power Plant was the culprit.

After an investigation at the plant, the bureau found that the coal used as fuel was substandard, causing dusting equipment in the boiler to malfunction, sending out an excessive amount of soot.

The soot mixed with rain and formed "black rain," according to an employee at the bureau.

(China Daily October 22, 2005)