In Mercer's 2015 annual quality-of-living survey, New Delhi ranks at number 154 out of 230 cities due to bad air quality and pollution. The World Health Organization ranked New Delhi as the world's worst polluted city in 2014 among about 1,600 cities the organisation tracked around the world. In 2016, United States Environmental Protection Agency listed New Delhi as the most polluted city on Earth and IQAir listed New Delhi as the world's most polluted capital city for the second straight year in year 2019. 