Authorities Guangzhou, capital city of southern China's Guangdong province, are facing a tough job to ensure better air quality during the upcoming Asian Games, as the event comes at a time of year that has been "relatively bad" for air quality in the city's history.

Sources with the Guangdong provincial environmental protection department said that Guangzhou reported "bad air quality" in October and November in the past four consecutive years.

Guangdong Water Sports Centre [File?photo]

The 16th Asian Games, the world's second largest sports event, will be held in this city on Nov 12 to 27 this year.

From October to December, every year for the past four years, 34 to 51 percent of the days have registered level III or lower level air quality in the city, official sources said.

The China Environmental Monitoring Center classifies air quality in urban areas into five levels, ranging from level I or excellent, level III or slightly polluted, to level V or hazardous.

Major pollutants included PM10 (particulate matter), PM2.5 and O3 (ozone), sources said.

"We should develop a long-term effective system in the Pearl River Delta cities to ensure better air quality," Lin Musheng, vice governor of Guangdong, was quoted as saying by Wednesday's China Daily as saying.

According to Lin, the Pearl River Delta region still reports heavy acid rains, although major air pollutants have decreased in many delta cities in the past several years.

Public concerns about air quality before this year's Asian Games have grown stronger after the city reported days of heavy haze and dust at the end of last year.

The city reported up to five consecutive days of haze and dust at the end of November, the heaviest in the past decade, sources with the weather authority in Guangdong said.

But provincial environmental authority officials said the air quality has improved in recent years, with haze and dust days reduced from 96 in the first half of 2008 to 46 in the same period of last year.

"Officials do not explain why we experienced poor air quality last year. How can they say the air quality has improved?" Huang Yunwen, a 63-year-old resident, said in an earlier interview with China Daily.

The local government has pledged to ensure at least 96 percent of days have better air quality this year ahead of the upcoming Asian Games.

"But it remains a hard job for the government to realize the goal if no prompt and effective measures are taken before the Games," Huang said.