Ensuring clean air will no longer be the task of a single city - it will be the responsibility of a cluster of cities whose pollutants affect each other, according to a plan being finalized by the government.

The plan is likely to include regional emission caps, Zhang Lijun, vice-minister of environment, told reporters.

He said the plans, which are being drafted, are expected to take effect from the beginning of the 12th Five Year Plan (2011-15).

Zhou said the three regions will take the lead because "they see concentrated air pollutant emissions, and suffer heavy air pollution".

According to ministry figures, the three regions occupy only 6.3 percent of the country's area but consume 40 percent of the country's coal and produce half of its steel. They are also home to at least 200 million people.

"However, because air pollutants are transient, the current plans of individual cities do not solve the problem," Zhou said.

A report from the National People' Congress' Environmental and Resources Protection Committee released yesterday shows about 30 percent of air pollutants in Beijing are from other places.

It also says acid rain, ozone and small particles occur more densely in these city groups than other parts of the country.

The Yangtze River Delta and the Beijing-Tianjin-Hebei region see heavy photochemical presence, a severe and dangerous pollution created as nitrogen oxides and hydrocarbons react to sunlight.

And the Pearl River Delta is suffering rising dust haze pollution, according to the report. It says the region saw more than 100 days of haze last year.

"Given the situation, air pollution controls based on a single city are costly and ineffective," Pu Haiqing, vice-chairman of the committee, said. "It's imperative for cities to join hands."

Zhang said the successful regional air pollution control measures adopted during last year's Olympic Games will be valuable experience for planning.

Beijing and neighboring municipality Tianjin as well as Hebei, Inner Mongolia, Shanxi and Shandong cut emissions to ensure clean air for the Games. The plan also covered the control of dust, automobile and industrial emissions, and coal consumption.

But Zhang Jianyu, China program head of the US-based Environmental Defense Fund, said temporary measures taken during the Games, such as traffic controls in Tianjin, could not be long-term solutions.

"Regional plans are obviously a step forward," he said. "But to ensure implementation, administrative measures alone cannot work."

Zhang said balancing the interests of different cities could be hard, so they must be accompanied by economic incentives or even legislation.

Meanwhile, at least two indices - ozone and particles less than 2.5 microns (PM2.5) - will be part of the air quality evaluation system to offer people a clearer picture of air quality.

The current evaluation system includes only three indices: Sulfur dioxide, carbon dioxide and particles less than 10 microns (PM10), but they do not reflect true air quality, the environment minister said.