5 Most Polluted Cities in the U.S.

4. Oklahoma City, Oklahoma

Insider Monkey’s Score: 10.25

Oklahoma City is the capital of Oklahoma. It is also the largest city in the state and has a population of almost seven hundred thousand people. The Oklahoma City metropolitan area has a population of 1.38 million people. Oklahoma is home to two Fortune 500 energy companies, and the Federal Aviation Administration is one of the largest employers in the area. It also has a presence of important food, beverage, and industrial companies.