China's health watchdog has vowed to expand the scope of air quality monitoring and invest more in researching the health impact of smog, as Beijing retains a pollution alert.

"The commission will strive for more financial support from the central government to expand air monitoring coverage while continuing to research the impact of smog on human health," said a statement released on Tuesday by the National Health and Family Planning Commission.

Heavy air pollution shrouded 58 of 161 cities monitored on Tuesday morning. Of the 58, 23 were "severely polluted," according to official figures.

At 5 p.m. on Tuesday, Beijing's average PM 2.5 index, which measures airborne particles smaller than 2.5 micrometers, hit 475 micrograms per cubic meter. That is within the most severe level, and high readings are expected to last until Thursday, when a cold front should disperse the pollutants.

Tuesday's statement cited key upcoming research projects coverings fields including precautionary technology for smog, smog-related diseases, and health risks for vulnerable populations.

According to the Ministry of Environmental Protection (MEP), Beijing, Tianjin and Shijiazhuang are required to publicize their analysis results on air pollution sources by the end of June, followed by more regions.

Experts hope these results will guide more precise efforts for air pollution prevention and control.

Meanwhile, the commission also promised to strengthen cooperation with environmental protection, weather and other departments in tackling smog.

More efforts will be made to promote education and consultation on the issue to guide the public to step up health protection, said the statement.

Also on Tuesday, the MEP noted various pollution problems in an official inspection of the city of Taiyuan in north China's Shanxi Province and Baotou, in the neighboring Inner Mongolia Autonomous Region.

It cited unscientific industrial distributions, obvious dust pollution in areas of urban-rural conjuncture, inadequate anti-pollution measures for construction sites and various local companies, but didn't say how to address these issues.