Estonia, Luxembourg and UK are the top three in biennial Yale University index in tackling pollution and other issues Much of the world has made encouraging strides in reducing toxic problems such as water and air pollution that have long plagued communities. But there is still a widespread lack of progress among countries in dealing with the climate crisis , according to the latest edition of an influential environmental scorecard. The biennial Yale University index again ranks Estonia as the best-performing of 177 assessed countries, after strong recent efforts to reduce its greenhouse gas emissions and protect its ecosystems.