China censors US embassy pollution data during APEC summit
A woman walks with her child on a street as schools were closed due to the heavy smog in China's Jilin province on October 22, 2013 (AFP)

Authorities have ordered one of China's most popular air pollution-reporting apps to remove data provided by the US embassy, a company spokesman said Tuesday, as Beijing hosts a high-profile gathering of world leaders.

The Chinese capital is periodically hit by choking, acrid haze, with particulate levels soaring far beyond recommended limits and public anger mounting over the issue.

While the city government provides its own air pollution data, a separate reading by the US embassy in Beijing is widely considered more reliable.

Beijing and neighbouring areas have sought to tamp down on pollution for the two-day Asia-Pacific Economic Cooperation summit by imposing tight limits on car use, ordering factories to close and giving public-sector employees holidays.

The gathering, which has seen 21 world leaders including US President Barack Obama and his Russian counterpart Vladimir Putin descend on Beijing, is the biggest event yet hosted by Chinese President Xi Jinping, who took office last year.

Vice Premier Zhang Gaoli had said before APEC that cleaning up the air was the "priority of priorities," according to the official Xinhua News Agency.

But Fresh-Ideas Studio, the developer of a widely-used pollution tracking app, told AFP on Tuesday that Beijing city officials had demanded US embassy data be removed from the app.

"We cannot continue to show air quality data released by the US embassy in our software," a representative of Fresh-Ideas Studio wrote in an e-mail. "We hope you can understand."

On Tuesday, the data was still accessible in China on the US State Department's website.

China had intended to cut pollution in the capital by as much as 40 percent during the APEC meeting. Xi even acknowledged the air quality issue at the summit's opening gala on Monday.

But pollution levels on Tuesday were still more than 10 times the World Health Organization's recommended level for 24-hour exposure.

"These days the first thing I do in the morning is to check the air quality in Beijing, hoping that the smog won't be too bad so that our distinguished guests will be more comfortable while you are here," Xi said at a welcome banquet for leaders and spouses.

It wasn't clear whether he was referring to official government air quality numbers or those of the US embassy.

"My hope is that every day we will see a blue sky, green mountains and clear rivers" throughout China, he added.

By the end of the dinner, pollution had hit levels considered "Very Unhealthy," according to US embassy figures.