It’s time to take a deep breath before you travel — or maybe not.

The latest statistics are out on which U.S. cities and regions have the most unhealthy air.

So which American city has the most polluted air? It’s not a big city.

It’s Bakersfield, California, locked in a valley with very little air movement combined with oil refineries and agriculture.

Coming in second and perhaps not a surprise is South Los Angeles, with many landlocked neighborhoods, rail yards and freeway interchanges.

Number three on the list is Chicago’s South Side.

Indiana makes the list twice with the northwest part of the state and central Indianapolis, followed by Houston Texas, St Louis and central Pennsylvania.

A surprise on the list is central Atlanta, and Birmingham, Alabama.