The least polluted place in the entire world is Stockholm , Sweden. It was awarded the honor is 2010 and just keeps getting better about its clean habits. It is one of the greenest cities in the world which helps keep it pollution free. Most of the energy it uses is green too. There are other cities that are almost as clean as Stockholm like Madrid, Spain and Wellington, New Zealand. These towns focus on being clean in the air they put off and keep trash picked up too. They have clean water, clean air and a clean ground.
The citizens are generally quite pleased with the recongition their city gains by being clean because people want to visit areas that are clean and want to do business with them too. India has the most polluted cities as they have 7 of the 10 worst ones. If you want to live clean, go to Stockholm and you will bask in the goodness of purity.
It is rather problematic to identify one single country as the least polluted because the lowest in one respect, for instance water, may not be the lowest in another, say, land pollution. However, if you go halfway between Australia and Hawaii, you come to the Marshall Islands and here is the lowest recorded air pollution.
Several cities or areas within countries lay a claim to lowest urban pollution. The cleanest air is Stockholm in Sweden. It's pollutant particles can only be seen under a microscope. Another city with a similar claim is in Northern Canada, Whitehorse. However, Kerala in India comes at or near the top for minimal pollution if air quality is not the only measure used for pollution.