We've all seen the brown cloud that hovers around Colorado's capital a time or two. If you have ever seen that and thought to yourself "Denver's pollution is bad," you are correct.

In fact, it is one of the worst in the United States.

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According to a report from BuyAutoInsurance.com, the Denver metro area has ranked 4th in the nation for air pollution.

The ranking comes from data compiled by the Environmental Protection Agency.

The top air pollution city was San Bernardino, CA. Phoenix, AZ., and Los Angeles, CA.

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Source: CBS Denver