Last
year: #3
Ozone
pollution rank: #1
Los Angeles's famously polluted skies normally top this list and always have the worst ozone pollution in the nation. Various geographical factors play a role in astronomically high pollution levels, but LA's terrible commute is the main culprit. A company called INRIX gathered data from GPS smart phone tracking to determine which areas in the country had the worst traffic, and Los Angeles earned the title. Nonetheless, the city is making progress. This year, it had the fewest number of high-ozone days since State of the Air reports began in 2000.
