The Yale University and Columbia University in collaboration with the World Economic Forum gather information to create The Environmental Performance Index (EPI). It used 24 parameters to ranks 180 countries all around the world.
The parameters are grouped by two different categories, environmental health and ecosystem vitality.
Some of the indicators used to check the environmental health are Lead exposure, drinking water, sanitation, water quality, air quality.
Marine protected areas, tree cover loss, CO2 emissions, wastewater treatment and sustainable nitrogen management are some of the indicators to evaluate the ecosystem vitality of the country.
The following graph shows the top 12 countries with the best environmental performance during 2018.