What country has the least pollution?
Iceland - Cleanest air in the world.
When it comes to air pollution Iceland is the country that has the cleanest air in the world and that can be credited to the sparse population and immense green cover. The country is located in Northern Europe and has the least population density in Europe.
refer link : Top 10 least poluted countries in 2017
the above link explains more on the topic of different countries and their pollution levels.