GUANGZHOU - Deteriorating air quality and more smoggy weather are troubling Guangzhou residents.

Guangzhou registered substandard air quality for only five days last year. However, in the first 91 days of this year there were six such days, according to the Guangzhou Bureau of Environmental Protection.

Yang Liu, deputy director of the bureau, said the weather is to blame.

"The average daily emission of pollutants in the first three months of 2012 was almost the same as during the same period in 2011," Yang told China Daily. "But the succession of cloudy days and rainy days increased the humidity and the lack of wind also made it difficult for the pollutants to diffuse."

The bureau released data on Guangzhou's environmental quality in 2011 and the first three months of 2012 on Monday.

The report shows that the average concentration of sulfur dioxide and nitrogen dioxide during the first three months of 2012 decreased by 25.9 percent and 5.6 percent respectively, compared to 2011.

The concentration of particulate matter 10 (PM 10, particulate matter with a diameter of less than 10 micrometers) increased by 10. 8 percent, a "slight" increase according to Yang.

Guangzhou was the first city in the country to publish real-time data for PM 2.5, starting on March 8.

The Canton Public Opinion Research Center conducted a survey of more than 1,012 Guangzhou residents concerning the government's monitoring of PM 2.5 in March and published the results on Monday.

Only 13 percent of the respondents said they thought that the data published by the government reflected their feelings about the air quality.

Many people complained that they felt that the air was dusty even when the data showed that the concentration of PM 2.5 was below the limit.

Chai Fahe, deputy director of the Chinese Research Academy of Environmental Sciences, pointed out that it is easier for cities in southern China to experience dusty air than cities in northern areas because of greater humidity.

"In cities in southern China, the air can become dusty when the concentration of PM 2.5 is higher than 30 micrograms per cubic meter. In northern cities, the concentration of PM 2.5 has to be higher than 75 micrograms per cubic meter," Chai explained at a seminar in Guangzhou on April 10.

In order to control air pollutants, the Guangzhou government has focused on cutting vehicle emissions.

The government inspected 715,000 vehicles during the last seven months of last year in order to detect heavy polluters. It also expanded the area where vehicles with heavy emissions are banned from 260 square kilometers to 353 square kilometers, beginning in October 2011.

Yang Liu told China Daily that the bureau is planning to add 8 to 10 new supervision sites for PM 2.5 in Guangzhou this year.

"In the coming 15 days, we will sample public opinion about the locations of these new sites," he added.