Raising air quality and the number of "blue sky" days remains the top environmental priority this year. Another is to clean up the soil.

Environment Minister Chen Jining said yesterday more will be done so that China's winter heating needs do not result in smog.

Speaking to reporters on the sidelines of China's annual political meetings, Mr Chen admitted that progress has been slow in reducing the concentration of PM2.5 particles over the Beijing-Tianjin-Hebei area during the winter months from November to March when China provides subsidised central heating to parts of the country.

PM2.5 particles are airborne particles considered the most harmful to health as they are tiny enough to enter the bloodstream.

China, which relies primarily on coal for heat and power generation, plans to speed up the retrofitting of its coal-fired power plants this year to be as clean as natural gas plants.

It has done so for half its coal-generation capacity, and intends to complete the overhaul by 2020.

With the air pollution problem considered somewhat under control, the government has begun its push to undo the damage that decades of unregulated industrialisation have done to its land.

This year, China will conduct its second national survey on soil quality, and introduce its first soil pollution law. The first survey released in 2014 found one-fifth of China's arable land unsafe for farming and described the situation as "severe".

Soil pollution is considered politically sensitive in China, as it is linked to farmers' livelihoods and public food safety concerns.

The country has been criticised for being vague about soil pollution data: at one point, it called parts of its 2014 survey a "state secret".

Then in May last year, China released a 10-point action plan to tackle soil pollution. Targets include ensuring that 90 per cent of contaminated farmland is safe by 2020, and 95 per cent by 2030. This came after earlier plans to fight air and water pollution.

Mr Chen defended China's record in curbing pollution as he faced a series of questions on public perception that progress has been slow.

Outside of Beijing, average PM2.5 levels fell by 30 per cent in 74 key cities last year compared with 2013, he noted.

He attributed the smaller reduction in Beijing to weather patterns such as weak winds that allow pollutants to accumulate in the air.

"The 30 per cent improvement is real (and) the progress we've made in the last three years is faster than in some developed countries," he said. "If... our government did not act, how could we have resolved so many issues faster than some Western countries?"