CAUSES

Meteorological experts with the country's National Meteorological Station said relatively high humidity, low winds and a lack of cold fronts had contributed to the recent foggy weather in many parts of China.

"But the fog holds no pollution itself. The problem is the discharge of a huge amount of pollutants into the air each day," said Yu Jianhua, an official with the Beijing Municipal Environmental Protection Bureau.

Beijing has a permanent population of around 20 million and some 5.2 million vehicles, with the number of private cars on the rise.

Like many other built-up areas, the growth of its economy, population and energy demands has brought more pressure to its pollution control.

Pollutants, some of which came from vehicle exhausts, have gradually accumulated in recent windless days in Beijing which is bordered by mountains to the north and west, Yu said.

Zhu Tong, an expert on environmental studies at Peking University, said no obvious improvement could be felt after one or two measures due to the accumulated pollutants in such large-scale smoggy weather.

"The heavy air pollution emergency response plan, which Beijing promulgated at the end of 2012, must be implemented strictly and in a timely way," Zhu added. "If the implementation is too late, the effects would be weakened."

The response plan stipulates measures based on the degree of pollution. For example, if the pollution reaches the worst level, earth and stone-related construction projects should be suspended and major polluting chemical companies should reduce their emissions by 30 percent via cutting production.

Meanwhile, environmental protection awareness must start with everyone taking concrete action to reduce pollution, experts believe.

"People should choose more public transport. Drivers should cut their engines after parking," said Zhu. "We should draw a lesson from the serious, lasting pollution."

China has invested heavily in reducing polluting emissions in recent years. It pledged in its 12th Five-Year Plan to cut energy consumption per unit of GDP by 16 percent while slashing carbon emissions by 17 percent in the five years to 2015.

"Adjusting industrial and energy structures is a must," said Wang Jinnan, chief engineer with the Chinese Academy for Environmental Planning.

"We need to realize the long and complicated process of PM2.5 treatment."

Beijing is aiming to cut emissions of major pollutants including sulfur dioxide, nitrogen oxides and ammonia nitrogen, by 2 percent from levels recorded last year.