China has effectively halted the rise of ozone pollution and stabilized its concentration levels as air quality continues to improve, the Ministry of Ecology and Environment said on Monday.

The country's average ozone density in 2024 was 143.6 micrograms per cubic meter, a decrease of 2.7 percent compared with 2019, said Li Tianwei, head of the ministry's Department of Atmospheric Environment.

The ministry aims to eliminate days with heavy pollution this year, despite expecting less favorable weather conditions, Li said, adding that it plans to further reduce emissions by advancing clean heating, ultralow emission transformation, volatile organic chemical controls and transportation sector management.

"We will holistically transform the structures of industry, energy consumption and transportation toward green, low-carbon development," he said.

The density of the pollutant has remained between 144 and 145 micrograms per cubic meter for three consecutive years, marking a turning point after years of increase, Li said. "This means the upward trend of ozone density since 2015 has been preliminarily curbed," he added.

According to the ministry, ozone pollution in China peaked at 148 micrograms per cubic meter in 2019, after rising steadily for several years.

While the ozone layer in the upper atmosphere protects humans against harmful ultraviolet radiation, ground-level ozone is a pollutant that can cause respiratory issues and lung damage even at relatively low concentrations.

Ozone pollution is most prevalent in summer. Ozone at ground level is formed when volatile organic chemicals and nitrogen oxides, partially from vehicle emissions, react in sunlight and under high temperatures.

Li said the stabilization of ozone levels coincides with China's overall improvement in air quality, helped by stricter pollution controls and favorable meteorological conditions, including fewer sand and dust storms.

Li credited the improvement to emission reduction efforts in key sectors, highlighting progress in the steel industry. Ultralow emission upgrades have been completed for 130 million metric tons of production capacity, he said, adding that more than 80 percent of the steel industry has been upgraded.

Despite economic challenges and external pressures, China's average concentration of PM2.5 — fine particulate matter linked to health risks — fell to 29.3 micrograms per cubic meter last year, down 2.7 percent compared with the previous year.

The proportion of days with "fairly good" air quality reached 87.2 percent in 2024, an increase of 1.7 percentage points from 2023 and the highest since 2021.

Meanwhile, the proportion of days with heavy pollution or worse in 2024 dropped to 0.9 percent, the lowest so far this decade and a year-on-year decrease of 0.7 percentage point.

houliqiang@chinadaily.com.cn