China Air Quality Trends – May 2026 Snapshot – Centre for Research on Energy and Clean Air

By Qi Qin, China Analyst; Miao Chien, Data Scientist; with contributions from Lauri Myllyvirta, Lead Analyst

After China tightened its PM2.5 standard, 16 provincial capitals still failed to meet the new limit by the end of May, with northern and northwestern cities facing elevated PM2.5 and multi-pollutant pressure. Yet, most capitals saw PM2.5 and NO₂ fall year-on-year in May, mainly due to lower emissions.

An agricultural machine harvests wheat in Dongyao Village, Jiaozuo City of central China’s Henan Province, on 31 May 2026. Photo: Xinhua/Alamy.

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 by the end of May. Non-compliant cities were concentrated not only in the Beijing-Tianjin-Hebei region but also across parts of the Northeast and Northwest.
PM2.5 levels rose year-on-year in only two provincial capitals in May, down sharply from 18 in March. Meanwhile, Zhengzhou and Shijiazhuang saw notable improvements, despite still ranking among the ten provincial capitals with the highest PM2.5 levels. The decline in PM2.5 was driven by a combination of weather conditions and lower emissions, with emission reductions playing the larger role.
Haikou, a southern provincial capital that typically enjoys relatively good air quality, saw notable year-on-year increases in both PM2.5 and ozone concentrations, mainly driven by higher emissions.
Several provincial capitals faced multi-pollutant pressure in May, with Lanzhou, Taiyuan, Tianjin, and Beijing ranking relatively high across more than one pollutant. Lanzhou stood out for having both the highest PM2.5 level and one of the highest NO₂levels, while Taiyuan ranked among the top cities for both ozone and NO₂.
Lower emissions were the main driver of PM2.5 and NO₂ reductions. For PM2.5, emissions-related changes contributed to declines in almost all provincial capitals except Kunming and Guiyang, while NO₂ reductions were driven by lower emissions across all cities, even where weather conditions were less favourable.

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

As of the end of May, 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 were still concentrated in the Beijing-Tianjin-Hebei surrounding area. Shijiazhuang (Hebei) recorded the highest levels at 42 µg/m³, followed closely by Zhengzhou (Henan) at 40µg/m³. Tianjin came next at 38 µg/m³.
Provincial capitals that failed to meet the national PM2.5 standard were also clustered in the Northeast and Northwest, including Shenyang, Changchun, Harbin, Urumqi, Xining, Yinchuan, and Lanzhou. Other cities on the list included Jinan, Wuhan, Chengdu, and Changsha, while Hefei, which exceeded the standard last month, returned to compliance.

PM2.5 levels rose year-on-year in two provincial capitals in May

Notable year-on-year increases were recorded in two capitals, namely Kunming (+15%) and Haikou (+2%), although both cities typically have relatively low PM2.5 levels.
The biggest year-on-year declines were recorded in Xi’an (-49%), Shenyang(-44%), and Jinan (-43%).
Other notable declines included Zhengzhou (-39%), Shijiazhuang (-34%), and Hefei (-33%).

Three provincial capitals exceeded the annual ozone limit

As of the end of May 2026, three out of 31 provincial capitals recorded 12-month 90th percentile ozone concentrations above the national standard of 160 µg/m³.
Cities with the highest ozone levels were still mainly located in the Beijing-Tianjin-Hebei surrounding area. Taiyuan (Shanxi) recorded the highest level at 167 µg/m³, followed by Shijiazhuang (Hebei) at 164 µg/m³, and Tianjin at 161 µg/m³.
Compared with the previous month, six capitals, namely Hohhot (Inner Mongolia), Lanzhou (Gansu), Harbin (Heilongjiang), Yinchuan (Ningxia), Urumqi (Xinjiang), and Taiyuan (Shanxi), saw slight increases in their annual ozone assessment values.

Ozone levels rose year-on-year in nine provincial capitals in April

Northwestern capital cities saw the largest year-on-year increase in ozone levels: Yinchuan (+7%) and Hohhot (+4%). Urumqi (+3%), Lhasa(+2%), and Lanzhou (+2%) also saw notable increases.
Haikou (Hainan) saw increases in both PM2.5 (+2%) and ozone (+4%) levels.
Many capital cities saw notable declines in ozone and PM2.5 simultaneously, including Xi’an, Hefei, Jinan, Shijiazhuang, Chongqing, and Zhengzhou.

Multi-pollutant pressure concentrated in northern capitals

Several provincial capitals faced multi-pollutant pressure in May, with Lanzhou, Taiyuan, Tianjin, and Beijing ranking relatively high across more than one pollutant. Lanzhou stood out for having both the highest PM2.5 level and one of the highest NO₂ levels, while Taiyuan ranked among the top cities for both ozone and NO₂.
Low-pollution cities tended to be southern, coastal, high-altitude, or less industrialised provincial capitals. Haikou, Lhasa, and Guiyang ranked among the lower end for at least two pollutants, especially PM2.5 and NO₂.

Emission changes drove most PM2.5 and NO₂ reductions

Lower emissions were the main driver of PM2.5 and NO₂ reductions. For PM2.5, emissions-related changes contributed to declines in almost all provincial capitals except Kunming and Guiyang, while NO₂ reductions were driven by lower emissions across all cities, even where weather conditions were less favourable.
For ozone, the emissions contribution was more uneven. Emissions-related increases were seen in cities such as Lanzhou, Haikou, and Yinchuan.

Worst 7-day air pollution episodes by pollutant

PM_2.5 (excluding sandstorms)

City	Province	Dates	Average concentration	Highest daily concentration
Deyang	Sichuan	May 09 – May 15	53.8917	86.1373
Hebi	Henan	May 11 – May 17	52.7349	67.175
Langfang	Hebei	May 09 – May 15	48.4359	57.3258
Nanyang	Henan	May 28 – Jun 03	46.2692	110.038
Zizhong	Sichuan	Apr 25 – May 01	45.7446	103.8472

Sandstorms (PM_2.5)

City	Province	Dates	Average concentration	Highest daily concentration
Pingliang	Gansu	May 20 – May 26	31.0366	104.497
Wuzhong	Ningxia	May 09 – May 15	28.0965	115.4807
Lanzhou	Gansu	May 16 – May 22	28.0302	125.6141
Shizuishan	Ningxia	May 09 – May 15	27.5652	120.4825
Baiyin	Gansu	May 16 – May 22	24.5506	109.2292

Ozone

City	Province	Dates	Average concentration	Highest daily concentration
Handan	Hebei	May 28 – Jun 03	194.0223	240.2813
Zaozhuang	Shandong	May 28 – Jun 03	193.6821	227.5
Binzhou	Shandong	May 28 – Jun 03	193.5286	253.575
Suzhou	Anhui	May 28 – Jun 03	192.8571	221.2083
Hengshui	Hebei	May 28 – Jun 03	192.5536	246.5

NO₂

City	Province	Dates	Average concentration	Highest daily concentration
Yangquan	Shanxi	Apr 25 – May 01	35.3205	41.9507
Tieling	Liaoning	May 25 – May 31	34.6861	50.7292
Siping	Jilin	May 25 – May 31	33.2888	45.9187
Dazhou	Sichuan	May 06 – May 12	32.9413	38.4091
Rizhao	Shandong	Apr 25 – May 01	32.7025	37.0565

Unit: µg/m³

Relevant analysis by CREA: