China’s top environmental official said today that the nation is still plagued by serious environmental degradation, though continuing efforts are being made to keep it in check. China, which is home to nine of the world’s 10 most polluted cities, is instituting a plan that requires 49 cities to reduce their air pollution to 1995 levels by 2000, or factories in those cities will be shut down. The government has already closed about 65,200 small factories across the country. China’s environment agency is gaining political influence in the central government, but still lacks enough power to implement significant changes. The World Bank estimates that the costs of pollution in China — including workers’ sick days, health care for pollution-induced ailments, and loss of forests and farmland — could be as high as 8 percent of the nation’s GDP, effectively canceling out the country’s economic growth.