"SHANGHAI - Not a single country managed to meet the World Health Organization's (WHO) air quality standard in 2021, a survey of pollution data in 6,475 cities showed on Tuesday, and smog even rebounded in some regions after a COVID-related dip.

The WHO recommends that average annual readings of small and hazardous airborne particles known as PM2.5 should be no more than 5 micrograms per cubic metre after changing its guidelines last year, saying that even low concentrations caused significant health risks.

But only 3.4% of the surveyed cities met the standard in 2021, according to data complied by IQAir, a Swiss pollution technology company that monitors air quality. As many as 93 cities saw PM2.5 levels at 10 times the recommended level."

David Stanway reports for Reuters March 22, 2022. [2]