When Li Jiangnan left his apartment on April 16 to get into his car, he was shocked to discover its color had changed overnight.

The Blue Sky Project, launched in 1998 in Beijing, have helped to visibly improve air quality in the past few years by reducing pollutants released into the city's skies.

The dark green vehicle had become yellowish a victim of the severe sandstorm from the Inner Mongolia Autonomous Region that hit the capital, which dumped 400,000 tons of dust.

Li, who has lived in Beijing for more than 20 years, said he had never seen such a heavy sandstorm before.

"I couldn't breathe," he said. "My nose was full of dust."

Bad weather conditions, including smog, have dented the authorities' efforts to improve air quality.

The Blue Sky Project, as it was dubbed by local media when it was launched in 1998, aims to address these problems. Initiatives taken under the project have helped to visibly improve air quality in the past few years by reducing pollutants released into the city's skies, said Tang Xiaoyan, a professor at Peking University who is also an adviser to the project.

The project has formulated an air quality index on three national standards: SO2 (sulphur dioxide), NO2 (nitrogen dioxide) and PM10 (particulate matter of 10 microns or less).

In short, if Beijing's pollution index is less than 100 in a day less than 150 milligrams/cubic millimeter of SO2; less than 100 milligrams/cubic millimeter of NO2 and less than 300 milligrams/cubic millimeter of PM10 it is considered a "blue sky day," according to the municipal environmental protection bureau.

The city met the goal of blue sky days at 234 in 2005, up from 177 in 2000. This year the target is 238.

But now, Tang said, the city has reached a critical point.

There were only nine blue sky days last month, and pollution levels were at their highest for four years.

From January 1 to April 17, Beijing reported 56 blue sky days, 16 fewer than the same period last year.

What is more, with Beijing's windy and dry spring comes dust caused by hundreds of construction sites in the city.

"I believe the sandstorm was a result of climate change," Tang said. "But we should try our best to reduce the polluting sources in the city."

Therefore, how to maintain the progress already made in Beijing is a priority on the government's agenda.

"But given its climate and geographical conditions, it is very difficult for Beijing to have even 5 percent more days of good air quality than it already has," said Zhai Xiaohui, spokeswoman for the bureau.

For about 40 days every year, particular weather conditions mean that pollutants cannot be diffused, and its location is like a dustpan, a natural habitat for sand and dust, Zhai explained.

But the municipal government remained determined to realize its goal, Beijing Party Secretary Liu Qi said at a televised conference last month. "No matter how difficult the task will be, there is no bargaining on the number of blue sky days in Beijing," he said.

The task in reducing pollutants varies from season to season. In spring and autumn, strict monitoring and supervision of construction sites and the transportation of waste is required in the city.

Liu has urged all construction sites in Beijing to cover the areas being worked on, press loose dirt into the ground and wash the wheels of vehicles when exiting the sites.

"We recently sent out all our staff to check the construction sites, and issued warnings and penalties to those who violated the regulations," said Li Rugang, director of the supervision team of the Beijing Municipal Law Enforcement Bureau of City Comprehensive Administration.

The monitoring task is enormous, with about 9,000 construction sites in the city. Samples have been taken at 280 sites in recent weeks, and 59 were found to have excessive levels of dust, Li said.

In total, about one-third of all construction sites in Beijing have been ordered to take remedial action recently.

"Some sites were found not to have b een covered, or that loose dirt had not been compressed," Li said.

Xuanwu District has set up 40 video surveillance monitors at construction sites to expand its own level of supervision.

The district's Environmental Protection Bureau said that 11 special environmental monitors have also been installed to monitor excessive outbreaks of pollution.

"Staff analyze the information 24 hours a day to locate the pollution sources," according to Li.

One of the major causes of pollution in Beijing comes from vehicles. It becomes an even graver issue in the summer time, when outdoor activities are at their peak.

Vehicle emissions account for 23 percent of the city's total air pollutants due to the rising number of cars in the capital, said Feng Yuqiao, director of the Vehicle Emission Department of the Municipal Environmental Protection Bureau.

To combat the problem, 7,100 old diesel buses and 35,000 ageing taxis were taken off the city's roads from 2000 to 2005. About 2,700 buses, which run on natural gas, were also introduced.

This year, Beijing Municipal Committee of Communication plans to take a further 8,000 taxis and 2,000 buses out of service.

But Tang said the city was not removing the worst polluting vehicles quickly enough.

In a survey last year, almost 30 percent of vehicles in Beijing's streets failed to meet the city's current exhaust release standards.

Feng said stricter emission standards on new vehicles and better control on the emissions of older cars was vital.

At the end of last year, the city upgraded its exhaust standard for vehicles from Euro II to Euro III, to make them cleaner.

"The new standard that bars polluting cars will help reduce the accumulation of pollutants in the city," Feng said, but added more still needed to be done.

Beijing has the largest number of vehicles on its roads in the country.

During winter, authorities face new challenges, when the burning of coal and gas becomes the biggest cause of air pollutants.

Large factories are the major culprits. In response, the municipal government restructured the city's industries and relocated some power plants to the outskirts of the city.

Some heavily polluting enterprises were even ordered to suspend production.

In further measures that have been taken, coal factories and coal processors are required to cover their manufacturing facilities to prevent dust from rising.

Apart from reinforcing pollution control, the use of innovative cleaner energy has been encouraged to replace standard coal for industrial use and heating systems.

Nowadays, of 16,000 large industrial boilers that used to burn coal in the city, more than 80 percent now use cleaner energy. According to the city's plan, by this October 1,400 more boilers will adopt cleaner energy.

It was Tang who proposed the Blue Sky Project in 1997 to the Beijing Municipal Environmental Protection Bureau.

And she still has a strong belief that the city will have more and more blue sky days in the coming years, including for the 2008 Olympic Games.

(China Daily May 12, 2006)