City with the least air pollution
Bredkalen, Wenden, Sinclair, Williston
2 microgram(s) per cubic metre
Not Applicable ()

As of April 2018, the World Health Organization’s Global Ambient Air Quality Database showed that four cities/towns have the lowest PM2.5 pollution per cubic metre, with an annual mean average of just 2 micrograms. These are: Bredkalen, Sweden; Sinclair, Wyoming, USA; Wenden, Arizona, USA; and Williston, North Dakota, USA.

The WHO Global Ambient Air Quality Database covers more than 4,300 cities and settlements in 108 countries.

The city with the worst air pollution according to the same dataset is Kanpur, India, with an average annual PM2.5 level of 173 (WHO's recommended threshold is 10 μ/m3).

PM2. 5 refers to atmospheric particulate matter (PM) that has a diameter of less than 2.5 micrometres – the tiny size of these particles makes them the most dangerous form of pollution as they can penetrate deeply into the lungs. A 2019 study estimated that air pollution kills as many as 8.8 million people globally per year.