BEIJING — China’s environment watchdog will monitor air quality changes in cities to gauge the success of measures to reduce pollution.

The Ministry of Environmental Protection said in a circular that it would establish a semi-annual and an annual index for air quality improvement and deterioration in cities.

The public will have access to air quality data of all major Chinese cities tracked by the ministry. The best and the worst ten cities will be updated regularly.

China has a nationwide network to track air quality levels in major cities and municipalities. The environmental watchdog currently publishes the best and the worst ten cities for air quality on monthly basis, which, according to the ministry, is insufficient to reflect a longer-term change of air quality.

Since cities have different industrial and energy structures, their air quality also differs.

In 2016, the PM 2.5 fine particle reading in Beijing-Tianjin-Hebei region, the biggest urbanized region in northern China, fell 7.8 percent from a year ago. However, nine out of ten worst cities are in this region.

Wu Jiyou, deputy head of the monitoring department of the ministry, said air quality improvement ranking could better reflect the commitment of the local authority to implement centrally-assigned anti-pollution measures.

PM 2.5 fine particles are a major pollutant in the haze that plagues many Chinese cities. They are linked to higher rates of chronic diseases.

China’s environmental protection still lags behind its economic status, as decades of breakneck growth have left the country saddled with problems such as smog and contaminated waterways and soil.

Northern China has frequently reported smog in winter, underscoring the fact that the war on pollution is an urgent, arduous task.

The country is aiming to reduce emissions in major cities by ten percent between 2012 and 2017. The PM 2.5 density in Beijing, Tianjin and Hebei province should drop by 25 percent.