9. Tallinn, Estonia
PM 2.5 annual mean, ug/m3: 8.22
Around 25% of Tallinn, the number 9 on our list of cities with the cleanest air in the world, is covered by large green urban areas, which helps in maintaining the high quality of air. There are three national landscape protection areas, two conservation areas, and around 61 parks. This city also implemented free public transport for citizens of Tallinn in order to encourage people to use public transportation and reduce air pollution.
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