BEIJING -- Beijing experienced just one day of heavily polluted air in 2025, a staggering reduction from 58 such days in 2013, the local environment authorities announced on Sunday, declaring a major victory in the city's battle against air pollution.

This indicates that heavily polluted days -- characterized by PM2.5 readings above 150 micrograms per cubic meter -- have been essentially eliminated in the Chinese capital, the Beijing Municipal Ecology and Environment Bureau said at a press briefing. PM2.5 readings, a key indicator of air pollution, are a gauge monitoring airborne particles of 2.5 microns or below in diameter.

In a landmark achievement, the city's annual average PM2.5 concentration in 2025 stood at 27.0 micrograms per cubic meter, marking the first time it has fallen below the 30-microgram benchmark since monitoring began.

Besides, throughout 2025, good air quality was recorded 348 days -- 144 days, or nearly five months more than in 2013 -- according to statistics released by the bureau.

This represents a significant departure from the past, as Beijing historically grappled with severe and frequent smog. Back in 2013, its annual average PM2.5 concentration reached 89.5 micrograms per cubic meter. Air pollution was once a major issue that impeded urban development and affected public well-being.

Confronted with this critical challenge, Beijing launched an unprecedented "blue sky defense war," according to the bureau.

The city has tackled pollution from mobile sources, coal combustion, industrial activities, fugitive dust and daily life sources, among other measures. Meanwhile, regional joint prevention, control and treatment of air pollution have been implemented across the Beijing-Tianjin-Hebei region.

However, experts warned that the recent improvements in air quality have not yet been fully secured, as regional emissions of atmospheric pollutants remain high. In such conditions, unfavorable weather factors, such as stagnant air during autumn and winter, can lead to the accumulation of pollutants, resulting in regional pollution.

Beijing will remain committed to its long-term goals, integrating air pollution prevention and control deeply into the overall socio-economic development framework, over the next five years, said Liu Baoxian, deputy director of the Beijing Municipal Ecology and Environment Bureau.

Liu added that the city will prioritize PM2.5 management, combine pollution reduction and carbon mitigation, and carry forward the "Every 0.1 Microgram Counts" initiative. The initiative was a follow-up to the "1 microgram initiative," launched in 2018, to improve air quality through refined control measures.

Nationwide, the Chinese government declared war on air pollution in 2013, launching its Air Pollution Prevention and Control Action Plan (APPCAP) -- a comprehensive national policy framework aimed at improving air quality.

Following the introduction of the APPCAP, China became the first developing country in the world to launch large-scale efforts to reduce PM2.5 concentrations, with Beijing leading Chinese cities by adopting scientific governance, institutional innovation and regional collaboration. The United Nations Environment Programme has hailed the megacity's achievements in improving air quality as the "Beijing Miracle."