Washington, May 14 : A new study has determined that in spite of the 2008 Olympic Games in sight, Beijing has not yet met the expected national air quality standards.

Professor Wang Wen-Xing and his team from the Chinese Research Academy of Environmental Sciences in Beijing carried out the study.

The purpose of their study was to inform measures to improve the air quality of the capital, in anticipation of the Olympic Games.

Wen-Xing and colleagues measured the concentrations of well-known air pollutants in Beijing in August and September 2007, the same summer period the Olympic Games will be taking place this year, in order to get a picture of the likely air quality during the games.

They compared their results against The National Ambient Air Quality Standard.

The researchers found that average daily concentrations of sulphur dioxide and carbon monoxide were lower than the National Ambient Air Quality Standard for China.

itrogen dioxide levels met the Standard, whereas concentrations of ozone and inhalable particles were higher than the Standard. The concentrations of air pollutants were also higher at night than during the day.

According to the researchers, the main causes of this air pollution are vehicle emissions.

Since the 1980s, the rapid industrial development, urbanization and increase in traffic have resulted in severe air pollution in Beijing. In recent years, the number of cars in Beijing has increased sharply at a rate of 10-20% a year.

This has resulted in weather conditions like dry air and lack of rain, which hinder the diffusion and deposition of pollutants.

A series of measures such as reducing vehicle emissions, encouraging the use of public transport, eliminating polluting factories, and improving fuel quality have been in place since 1998 to reduce the emissions and concentrations of air pollutants in Beijing.

These measures have already significantly reduced air pollution in the Chinese capital.

However, in comparison to other Olympic sites around the world, including Helsinki and Los Angeles, Beijing's air quality needs to improve, according to Wen-Xing.