Smoggy weather has become a lingering problem in China and the country faces a tough battle in its fight against serious air pollution, especially the northern parts, analysts argue.

On Wednesday, the 10 most-polluted cities included the municipalities of Beijing and Tianjin, as well as six cities in adjacent Hebei Province, according to the Air Quality Index released by the China National Environment Monitoring Center (CNEMC).

Tangshan, a city in Hebei that is 150 km east of Beijing, topped the list. The data is latest evidence of the poor air quality in Beijing, Tianjin and the surrounding areas.

Since the beginning of 2013, the center has monitored 74 cities around the country for major pollutants including sulfur dioxide, nitrogen oxides, inhalable particles, ozone, carbon monoxide and fine particles.

During the third quarter, in Beijing, Tianjin and 11 cities in Hebei, air quality for 62.5 percent of total days was below the CNEMC's standards, double the 31.1 percent for all other monitored cities around the country.

This is no coincidence.

The northern region, especially Hebei, has long been known for its steel industry, which contributes to a large proportion of GDP but also to air pollution.

Iron and steel production capacity in Hebei stood at 314 million tonnes in the first half, representing a third of the country's total, said Xu Xiangchun, an analyst with Mysteel.com, a leading steel information provider.

The capacity in Tangshan, a city rich with iron ore resources, exceeded 120 million tonnes, Xu said.

Wang Yuesi, a researcher with the Chinese Academy of Sciences, said more than 20 percent of PM2.5 pollutants in Beijing came from outside the city, according to his own research.

PM2.5, airborne particulate measuring less than 2.5 microns in diameter, can be inhaled by people and pose health hazards.

The proportion will be even higher during smoggy days when the air flow is relatively slow, Wang said.

His findings are backed by Guo Bin, a professor at Hebei University of Science and Technology.

After comparing the PM2.5 data at 300 monitoring points in Beijing, Tianjin and Hebei, Guo found the monthly changes in PM2.5 figures of the three regions to be similar, showing a close connection of air pollution in the areas.

"This means Beijing, Tianjin and Hebei must collaborate with one another in combating smog, and no region can be immune from influences of other regions," Wang said.

In September, the government released a plan for air pollution monitoring and early warning in Beijing, Tianjin, Hebei and some surrounding areas in a bid to intensify cooperation in the emergency response to heavily polluted air.

However, experts say coordinating efforts of local governments is not going to be easy, and the fight for blue skies will be a protracted task for the country.

In Hebei, the provincial government plans to cut its steel production capacity by 60 million tonnes by the end of 2017 to improve air quality.

Calculations by Mysteel.com showed that eliminating each tonne of steel capacity means a loss of more than 3,000 yuan ($488).

Cutting 60 million tonnes of capacity will result in a loss of 200 billion yuan, in addition to the loss of many jobs.

"Who is going to foot the bill for such enormous a loss and the burdens that may come along?" Guo said.

The air pollution issue must be tackled along with the transformation of the region's industrial structure, Guo said, adding that more developed parts should help with the structural upgrading to compensate the loss of economic growth and jobs in less-developed places.

Song Laizhou, a professor with Yanshan University in the city of Qinhuangdao of Hebei, said government efforts alone will not be enough in the fight against smog.

The country should establish a way for polluting companies to actively engage in pollution control, including offering bonuses for pollution reduction and allowing the trading of emission rights, Song said.

Song also urged for better laws to specify a company's obligations in order to force them to take initiatives in reducing pollution.