SHANGHAI - China's largest metropolis has suffered from high levels of pollution since early November, with pollution index figures far higher than those recorded during the six months of the World Expo.

As of Wednesday, the city has witnessed its air pollution index passing 100 for eight days this month, the worst readings in the past five years.

China's environmental standards rate a reading below 50 as "excellent", from 50 to 100 as "good" and above 100 as "polluted".