By Xiaoli Zhang, Qi Qin; Data scientist: Miao Chien; with contributions from Lauri Myllyvirta, Lead Analyst

A view of the ancient city wall in Zhengding, Shijiazhuang, north China’s Hebei province, Aug. 21, 2026. Photo: Imaginechina/Sipa USA

Key findings

Following the tightening of China’s annual PM2.5 standard from 35 to 30 µg/m³ in March 2026, the number of provincial capitals failing to meet the standard rose sharply from six at the end of February to 18 by the end of March, and remained high at 16 through May to August. Non-compliant cities were persistently concentrated in the Beijing-Tianjin-Hebei region and northeastern provinces.
PM2.5 levels rose year-on-year in 18 provincial capitals in August, compared with only two in May when weather conditions were more favourable. Further air-quality improvements will depend increasingly on structural changes in energy, industry, and transport; otherwise, pollution can rebound quickly when weather turns less favourable.
Haikou, a southern provincial capital that typically enjoys relatively good air quality, saw notable year-on-year increases in ozone concentrations, driven by higher emissions and unfavourable weather. Favourable weather conditions in the Yangtze River Delta helped drive down ozone concentrations.
Lower emissions contributed clearly to declining NO2 levels across most provincial capitals. Only five cities—Hefei, Xining, Lhasa, Beijing and Nanjing—saw emissions contributing to higher NO2 concentrations.

Sixteen provincial capitals failed to meet the new annual PM2.5 standards

As of the end of August, 16 of China’s 31 provincial capitals had 12-month average PM2.5 concentrations above the national annual standard of 30 µg/m³, meaning they failed to meet the standard. Starting this March, the new national standard for PM2.5 has been tightened from 35µg/m³ to 30 µg/m³.
The cities with the highest PM2.5 levels remained concentrated in the Beijing-Tianjin-Hebei surrounding area. Shijiazhuang (Hebei) and Zhengzhou (Henan) recorded the highest levels at 41 µg/m³ and have topped provincial capitals every month so far this year. Tianjin came next at 38 µg/m³.
Provincial capitals that failed to meet the national PM2.5 standard were mainly concentrated in Northeast China and key air-pollution control regions, including the Beijing-Tianjin-Hebei surrounding area and the Fenwei Plain.

The largest year-on-year increases were recorded in Chengdu (+39%), Changchun (+38%), and Zhengzhou (+38%), with Chengdu and Changchun also topping the list in July.
The biggest year-on-year declines were recorded in Yinchuan (-29%), Lanzhou(-21%), and Lhasa (-20%).

As of the end of August 2026, five out of 31 provincial capitals recorded 12-month 90th percentile ozone concentrations above the national standard of 160 µg/m³.
Tianjin recorded the highest level at 167 µg/m³, followed by Taiyuan (Shanxi) at 163µg/m³, and Shijiazhuang (Hebei) at 162 µg/m³.
All five non-compliant capitals were still in northern China, underlining the persistence of regional ozone pressure across the Beijing-Tianjin-Hebei region and nearby inland provinces.

Southern and western capital cities saw the largest year-on-year increase in ozone levels: Haikou (+50%) and Kunming (+23%), Xining (+18%), Nanning (+17%), and Lanzhou (+12%).
The Yangtze River Delta, one of China’s key regions for sustained air-quality improvement, recorded the largest year-on-year declines in ozone levels, led by Shanghai (-36%), Hangzhou (-24%), and Nanjing (-16%).
Oil displacement from electric vehicles and public transport helped drive a marked decline in urban NOx levels in China following the Strait of Hormuz shipping crisis.

Provincial capitals in the Beijing-Tianjin-Hebei region and surrounding areas generally recorded high concentrations of all three pollutants.
Low-pollution cities tended to be southern, coastal, high-altitude, or less industrialised provincial capitals. Haikou and Fuzhou ranked among the lower end for all three pollutants.

Emissions had a significant influence on changes in PM2.5 levels across provincial capitals in August. The impact was most pronounced in Zhengzhou, Wuhan, and Changchun, where emissions contributed most strongly to higher PM2.5 concentrations.
Favourable weather conditions in the Yangtze River Delta helped drive down ozone concentrations. In Haikou, both unfavourable weather and rising emissions contributed to the largest year-on-year increase in ozone levels.
Lower emissions contributed clearly to declining NO2 levels across most provincial capitals. Only five cities—Hefei, Xining, Lhasa, Beijing, and Nanjing—saw emissions contributing to higher NO2 concentrations.

PM_2.5 (excluding sandstorms)

City	Province	Dates	Average concentration	Highest daily concentration
Yangquan	Shanxi	Aug 19 – Aug 25	43.5195	47.4416
Deyang	Sichuan	Aug 31 – Sep 06	39.9528	69.1944
Guang’an	Sichuan	Aug 20 – Aug 26	38.9798	47.0729
Chengdu	Sichuan	Aug 31 – Sep 06	38.8718	55.1672
Neijiang	Sichuan	Aug 31 – Sep 06	38.5841	60.1805

Ozone

City	Province	Dates	Average concentration	Highest daily concentration
Tongliao	Inner Mongolia	Jul 26 – Aug 01	170.9167	247.3333
Linfen	Shanxi	Aug 31 – Sep 06	165.8214	183.125
Tai’an	Shandong	Aug 31 – Sep 06	165.3512	193.8958
Huludao	Liaoning	Jul 28 – Aug 03	165.2039	181.4375
Xi’an	Shaanxi	Aug 31 – Sep 06	164.5554	183.475

NO₂

City	Province	Dates	Average concentration	Highest daily concentration
Baotou	Inner Mongolia	Aug 30 – Sep 05	30.1492	37.59893
Meishan	Sichuan	Aug 31 – Sep 06	28.88111	31.79545
Huludao	Liaoning	Aug 30 – Sep 05	28.06155	36.53125
Yanquan	Shanxi	Aug 31 – Sep 06	27.77613	31.21827
Yulin	Shannxi	Aug 27 – Sep 02	26.82144	33.7803

Unit: µg/m³

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