People may think the air quality is worse, now that data based on stricter standards are released. But air quality may, in fact, be the same as in the past, when there was no official data to indicate such serious levels of pollution, according to Zhu.

"I think one of the things that's good to see is that the Chinese government, itself, has decided to monitor smog levels and publicize the results. So, that's a significant start in terms of taking care of the health and welfare of their own people on this issue," U.S. State Department spokeswoman Victoria Nuland said in a daily press briefing on Monday.

She said China being transparent to the Chinese public is a good step, as well as a positive response to the people's requests for more information. She also said the U.S. Embassy in China will continue to monitor the air quality and publish the results.

The Chinese government enacted new air quality standards in February last year, which included indices for ozone and PM2.5. The new standards came in response to fierce public debate that was stirred in 2011, when people took notice of the huge discrepancies between the air quality data published by the U.S. Embassy in Beijing and that of local environmental agencies.

According to media reports, the U.S. Embassy in Beijing generally published worse results than Beijing's weather forecasting station due to different measuring standards for PM2.5.

Starting Jan. 1, 74 major Chinese cities began issuing real-time PM2.5 readings and other air quality monitoring data.

But just releasing data is not enough, said Zhu.

To speed up the eradication of heavy pollution and avoid the recurrence of smoggy days, Zhu hopes the country will mete out stricter measures to limit coal burning and reduce emissions of pollutants, which are believed to be the main reason for the lingering fog.

Jimmy Green, an American who has been working in social media in China for three years, said he was happy about China's transparency in releasing environmental data and the rising monitoring standards.

"Although I, myself, still suffer from the terrible fog, I can feel the government's resolution to change," he added.