"However, before the Olympics or during the process of the Olympics, we will conduct strict management on the air quality in Beijing," said Sui, without elaborating.

It is estimated that there are more than one million migrant workers in the city and that that 300,000 figures involved in Olympic venue construction.

To ease worker's concerns about welfare, the city's municipal government has also taken measures to ensure wages are paid on time by sub-contractors involved in venue construction, according to Sui.

"Great importance has been attached to this issue, and construction projects have been inspected to check whether salaries have been paid or not," he said.

Beijing's skyline is dotted with thousands of construction cranes, and Olympic construction is just a small slice of the city's makeover.

Beijing plans to build or refurbish 31 venues in the city for the Games, which will take place from August 8-24, 2008.