The state of California is divided geographically into 15 different “air basins” in order to regulate air emissions on a regional, rather than a local basis. The divisions were decided upon based on both geographically like features (in some cases “air basins” are literally geographic basins surrounded by mountains) and by political boundaries, such as counties. While air quality can vary from basin to basin, emissions and pollution are obviously not confined to air basin boundaries.

The nine county Bay Area makes up its own designated air basin, the “San Francisco Bay” air basin. This basin is home to the second largest metro population in the state and is characterized by high vehicle miles traveled, several regional airports and industrial activity. Being a coastal region, wind and weather patterns can have a dramatic effect in transporting the pollution from the region into inland areas.

To find out more about the San Franciso Bay air basin and the 14 other air basins in California, visit the Air Resource Board’s interactive map here, get the latest air quality reports for your region from the annual California Almanac of Air Quality and Emissions, and check out a list of 50 things you can do to improve California’s air quality, here.

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