THE WATER CONTAMINATION CRISIS IN LANZHOU is drawing to a close, but the psychological shadow it has cast, not only over the city itself but also other parts of the country, will take longer to fade away.

Oil leaks from a petrochemical plant in the vicinity of a water transport canal in 1987 and 2002 were said to be the culprits for the contamination. This has increased many people's doubts about how safe the tap water they drink every day can be.

If oil leaks a long time ago can contaminate a city's drinking water, what about the sewage many cities discharged directly into rivers or even ditches without being treated and the pollutants industrial enterprises have dumped wherever they considered it convenient?