What is the most polluted country in the world?

According to a World Health Organization 2014 report, the most polluted country in the world is Pakistan with a PM2.5 pollution rating of 101 ug per cubic meter. The PM2.5 pollution rating measures the presence of fine particle pollution with a diameter of 2.5 micrometers or less.

Pakistan's pollution results in approximately 80,000 hospital admissions in addition to five million lower respiratory cases among children under five. Pollution in Pakistan also results in thousands of adult deaths annually and is the cause for approximately 8,000 cases of chronic bronchitis. Pollutants that make up Pakistan's pollution include particles such as smoke, pollen, mold and dirt.