What is the purpose of special economic zones in china?

Special economic zones in China, India and other developing nations are an advantage to these nations. Despite much progress in the countries mentioned above, highly industrialized nations such as Japan, the USA, and in Western Europe as example, are expected to decrease pollutants produced domestically by the use of advanced technology. There is a cost factor involved that lesser developed nations do not have to pay. Special "economic zones" in the developing nations are exempt from the constraints that the more highly developed nations are. This is said with the knowledge that these special zones are being decreased in nations that are showing dramatic economic growth. China, as example produces more air pollutants from its city of Shanghai, despite cleaner production costs there. One only needs to examine the GDP & GNP of China and other countries to see that they are still far below the "West". In fact, reliable data from China is not easy to verify.