With average densities of some major pollutants down to their lowest levels in years, China experienced "unimaginable" improvement in air quality in the first quarter of this year, mostly because of decreased production amid the novel coronavirus pneumonia epidemic, an environmental official said.

Liu Bingjiang, head of the Ministry of Ecology and Environment's Air Quality Management Department, also said emissions of pollutants had not jumped last month, when many factories resumed production.

"The improvement in air quality in the first season was extraordinarily marked," Liu told a news conference on Friday. "The densities of all air pollutants stood at a comparatively low level compared with previous records for the same period."

Emissions of sulfur dioxide, nitric oxide, particulate matter and volatile organic compounds all dropped by over 20 percent in the first quarter. The average concentration of nitrogen dioxide fell to the level of the 1990s, he said.

The percentage of days with fairly good air quality during the first three months of the year increased by 6.6 percentage points year-on-year, Liu said.

"This is something unimaginable," he said, adding that the country had only targeted a 3.3 percentage point improvement in the number of days with fairly good air quality during the 13th Five-Year Plan (2016-20).

The plunge in factory activity during the epidemic was a major reason for the vast improvement, but the country's long-term efforts in enhancing air management and favorable meteorological conditions also contributed, Liu said.

"Since the country rolled out a three-year campaign on safeguarding the blue sky, marked achievements have been made in adjusting the structures of industry, energy consumption, transportation and land use," he said.

The emission of pollutants had been declining gradually thanks to efforts to shed excess production capacity, transform coal-fired power plants to achieve extra-low emissions and shut down small, polluting enterprises, Liu said.

The ministry said Hebei province reduced its steel production capacity by 14 million metric tons last year, while Shanxi province's coke production capacity fell by 10 million tons.

Liu dismissed concerns there had been a general increase in emissions of pollutants as factories resumed production.

Analysis found that the year-on-year rise in the country's average density of PM2.5 particulate matter last month occurred because of a sharp increase in the burning of crop stubble in northeastern China and dust caused by dry weather in the Xinjiang Uygur autonomous region, he said.

Many local governments have ramped up efforts to implement the new development philosophy and promote green development, he said. Statistics showed the country will see fewer new projects this year that consume lots of energy, produce lots of emissions and are resource-intensive, which "has greatly relieved the pressure to further improve air quality".

Asked whether the ministry would lower the targets for air pollution control in the next cold season, Liu said the past heating-supply season was not a suitable base to draft new targets, considering the decreases in pollutant emission due to the pandemic.

The heating-supply season, which lasts from November to March in many regions in northern China, sees the most serious air pollution because of the use of coal for heating. As a result, it is common practice for the ministry to set targets for the period to enhance air pollution control.

Liu said the ministry will set "scientific and reasonable" targets for local governments by considering all the air quality conditions in recent cold periods.