POLLUTION is hindering urban progress and the key to solving the problem is balanced development, a top Chinese environment official said yesterday. Five out of the world's seven most polluted cities are in Asia, and China is host to the majority of these, said Dr Qu Geping, chairman of the Environmental Protection Committee of the National People's Congress. He was speaking to the week-long World Congress on Urban Growth and the Environment which opened yesterday in Hong Kong. Inadequate infrastructure for environmental protection, a lack of urban planning and an inefficient urban management system had caused the problem to worsen, Dr Qu said. 'The environmental quality of most Chinese cities is still poor compared to most of their counterparts in developed countries,' he said, adding that a 'sustainable development' was needed. Since the second half of the 1980s, both the number of cities and the urban population had mushroomed. The number of Chinese cities has more than doubled during the past 13 years. Meanwhile, urban population has grown from 191,400,000 in 1980 to 333,570,000 last year. Dr Qu said China had already formulated a policy to control the population of big cities while also focusing on the development of small and medium-sized cities. Surplus rural labour could be directed towards smaller nearby cities, he said. He said the setting up of functional zones within cities was another 'positive' way to solve the conflicts of development and environmental protection.