What are the world's dirtiest cities?

New York City, (officially the City of New York and also known as The Big Apple) is the largest city in the United States and one of the world's major global cities. Located in the state of New York, the city has a population of 8,213,839 within an area of 321 square miles (approximately 830 km²), making it the most densely populated major city in North America. With a population of 18.7 million, the New York Metropolitan Area is one of the largest urban areas in the world.