DENVER (CBS4)– Denver’s skyline is one of the most scenic in the nation but it’s still among the worst polluted in the nation.

According to the American Lung Association’s annual Clean Air Report, Denver ranks as having the 11th worst ozone levels in the nation. Fort Collins came in 15th.

The brown cloud over Denver (credit: CBS)

While the rankings aren’t great, both cities improved over last year.

Los Angeles was the city with the worst ozone pollution. Bellingham, Washington was considered the cleanest.