No country met the updated WHO PM_2.5 guideline in 2021

24 March 2022

Only three percent of cities and no single country met the latest World Health Organization’s (WHO) PM_2.5 annual air quality guideline, according to the 2021 World Air Quality Report by the Swiss air quality technology company iQAir. The report is based on PM_2.5 air quality data from 6,475 cities in 117 countries, regions and territories around the world.

Fine particle pollution, known as PM_2.5, is commonly accepted to be the most harmful, widely-monitored air pollutant, and has been found to be a major contributing factor to health effects such as asthma, stroke, heart and lung diseases. Last year, the WHO released an ambitious update to its global air quality guidelines, reducing the recommended annual PM_2.5 concentration by half, from 10 µg/m³ down to 5 µg/m³.

The key findings of the iQAir report are:

• No country met the latest WHO air quality guideline for PM_2.5 in 2021.
• Only the territories of New Caledonia, U.S. Virgin Islands and Puerto Rico met updated WHO PM_2.5 air quality guideline.
• Only 222 out of 6,475 global cities covered in the report met updated WHO PM_2.5 guideline.
• 93 cities in the report had annual PM_2.5 concentrations exceeding 10 times the WHO PM_2.5 guideline.
• Of 174 Latin America and the Caribbean cities, only 12 (7%) met the WHO PM_2.5 guideline.
• Of 65 African cities, only one (1.5%) met updated annual WHO PM_2.5 guideline. 
• Of 1,887 Asian cities, only four (0.2%) met updated WHO PM_2.5 guideline.
• Of the 1,588 cities in Europe, only 55 (3%) met the WHO PM_2.5 guideline.
• The report covered 2,408 cities in the United States and found that average PM_2.5 concentrations rose from 9.6 µg/m³ to 10.3 µg/m³ in 2021 compared to 2020. Of the major cities in the United States, Los Angeles was the most polluted. However, the City of Angels saw an overall decrease in PM_2.5 pollution of 6% compared to 2020.
• The top five most polluted countries in 2021 were: Bangladesh, Chad, Pakistan, Tajikistan, and India
• New Delhi (India) is the world’s most polluted capital city for the fourth consecutive year followed by Dhaka (Bangladesh), N’Djamena (Chad), Dushanbe (Tajikistan) and Muscat (Oman).
• Air quality in China continued to improve in 2021. More than half of the cities in China included in the report saw lower levels of air pollution when compared to the previous year. Pollution levels within the capital city of Beijing continued a nine-year trend of improved air quality, driven by emission control and reduction of coal power plant activity and other high emission industries.
• Central and South Asia had some of the world’s worst air quality in 2021 and was home to 46 of the world’s 50 most polluted cities. The only two cities that met updated WHO PM_2.5 guideline were Zhezqazghan and Chu (Kazakhstan).
• Air quality monitoring remains sparse in Africa, South America and the Middle East, although progress has been made by low-cost air quality sensors often operated by non-profit organizations and citizen scientists.

Source: IQAir