SHANGHAI - The air quality in Shanghai was "good" or "fair" on more than 98 percent of the days between May 1 and Aug 31, the best ever, all thanks to the environmental protection initiatives taken before and during the Expo 2010 Shanghai.

The average concentrations of sulfur dioxide (SO2), nitrogen dioxide (NO2) and PM10, or particles smaller than 10 microns, were reduced by 27.6, 8.9 and 13.9 percent respectively compared with the same period last year, according to the Shanghai Environmental Protection Bureau.

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Figures show that the quality of air on more than 95 percent of the days in the first eight months of this year was recorded as "good" or "fair", meaning the city's air quality index reached grade II or better.

The city has so far lived up to its aim of witnessing more than 95 percent of days with "fair" air quality this year.

Since the Expo kicked off on May 1, the municipal government has prohibited the burning of straws in suburban and rural areas, which is considered a major reason for the improved air quality.

Farmers used to burn redundant straws, releasing huge amounts of SO2 and carbon dioxide (CO2), two major air pollutants.

This year, the Shanghai Environmental Monitoring Center has used a satellite remote sensing technology to monitor and control the burning of straws.

Only 19 such cases were detected in May and June - the peak season to burn straws.

Air quality in the city proper has also improved significantly due to the reduction in automobile exhaust gas.

Statistics show that the tail gas of 9,000 out of the 16,000 buses in Shanghai have reached national standard III, the second highest in the four-level evaluation system, while the remaining 7,000 reached national standard II.

In addition, 90 percent of the 50,000 taxis in the city have reached national standard III.

However, dark smoke released by long-distance buses is still a common phenomenon.

According to the environmental monitoring authority, about 10 percent of long-distance buses release dark smoke.

All long-distance bus companies in Shanghai have been required to use the national standard IV oil, which helps reduce exhaust gas, in all their buses.

The city's environmental protection authority has also cooperated with its counterparts in the Yangtze River Delta to monitor buses that are still letting out dark smoke.

The Shanghai Environmental Protection Bureau has ordered diesel trucks with a load capacity of more than 3.5 tons to reach national standard IV by Jan 1, 2011, and all others by July 1, 2011.

"We will maintain the air quality even after the Expo comes to a close by continuous cooperation with other cities in the Yangtze River Delta and reducing the practice of burning straws," Zhang Quan, director of the bureau, said.

"I can feel the improvement in Shanghai's air quality this year," said Conny Feng, who works in a human resource outsourcing company.

"But I hope I can see more greenery in the city," she added.

"Trees and grass help purify the air in a more natural way. Besides, they also add to the beauty of a city," she said.