Compared with plastic, bags of other materials, including those made of paper and cloth, do not have the same advantages. And they could also cause environmental problems. Paper is made from trees; papermaking and textile are both industries producing huge amounts of sewage, which might pollute rivers and seas.

Moreover, paper and cloth bags are not easy to carry around. Convenience is an important element to change consumers' preference, which is why supermarkets have largely replaced the traditional retail outlets.

It is hard to imagine customers walking out of supermarkets or small shops with hands full of grocery items. Nor is it realistic to expect people take cloth or paper bags every time they go shopping. Moreover, the cloth bags need to be washed now and then, while the paper bags cannot be used to carry heavy things.

There is a view that the State ban against plastic bags goes beyond reducing the number of plastic bags, and actually advocates conservation of resources, natural lifestyle and environmental protection.

It is true that everyone wishes to live in a good environment. However, it is also necessary to stress that economic development, public welfare and environmental protection have a complex relationship among themselves.

Most of our manufacturing and consumption, such as papermaking and automobiles, have environmental influences.

Most people condemn pollutant producers in ethical terms. But the polluters did not produce just to destroy the environment, but to satisfy the demand of consumers. In a sense, the environment is an indispensable input for economic development.

The consumers should also realize that pollution is inevitable, though the degree differs, when they require the industries to produce certain commodities they need.

A renowned economist said that tolerance to dirtiness is a precondition for getting rich. It is true. When the economy develops to a relatively high level, people become less tolerant to environment problems and are more ready to pay the costs of protecting environment.

This process is what we call "pollute first and treat later". Definitely, it is not economical, but the experiences from economic development across the world prove it is hard, or even impossible, to avoid.

The environment protection has a close relationship with economic development and it could not go beyond the latter.

By now, several developed countries have restrictions about production and distribution of plastic bags, but few have the same harsh stipulations as that in China. Do they not worry about the environment risk of plastic bags? They did not ban the bags as we did for they found their alternatives might be even more costly.

It is reported that the Chinese consumers use 3 billion plastic bags every year, which need 13,000 tons of crude oil to produce. If this oil was saved from producing plastic bags, how could they be used? As fuel for automobiles? Is this change less threatening to the environment or is it more decent in ethical terms? As long as it is spent to boost consumer interests or public welfare, the oil has not been wasted.

As a national law, the plastic bag ban should be abided by in metropolises as well as in small towns. But the supervision over its full implementation might be difficult. If those violating the rule in cities are punished while those in remote areas are not, it would obviously harm the authority of the law.

Reducing the use of plastic bags is, of course, an environment-friendly move, but it should be carried out with proper arrangements. It would have been more convenient to consumers if the ban had been issued after practical alternatives to plastic bags were made easy to get and substantial improvement was made in recycling plastic bags.

About two decades ago, it was proposed that disposable chopsticks should not be used in order to protect the forests. And several rules and regulations were issued to support it. However, disposable chopsticks are everywhere to be seen even now. Let us wait and see whether the plastic bag ban would be better observed.

The author is deputy director of the Center for Financial Research, Beijing University of Aeronautics and Astronautics

(China Daily June 18, 2008)