15. Singapore
PM 2.5 annual mean, ug/m3: 18
Singapore is the best example of a country which reached the very top of the list of cleanest countries in the world by legislation. Fines for throwing litter go up to $5,000 and the offender might be asked to wear a sign that reads: “I am a litter lout.” Although this country aims at reducing pollution to a minimum, occasional rise in air pollution places it at the bottom of our list of 15 cities with the cleanest air in the world.
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