Denver tops list of most-polluted cities in the world

IQAir said particulate matter levels were 11 times the World Health Organization's exposure recommendation.

DENVER — Denver topped the list of the most polluted major cities in the world Saturday on the air quality tracking website IQAir.com.

The site said Denver's Air Quality Index (AQI) was as high as 179 (Unhealthy) as of the time of this writing, with a PM2.5 (fine particulate matter) concentration that was 11 times higher than the World Health Organization's (WHO) exposure recommendation.

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IQAir recommended wearing a mask outdoors, closing windows, avoiding outdoor exercise and running an air purifier as ways to protect yourself from air pollution.

The Colorado Department of Public Health and Environment (CDPHE) rated Denver's visibility as extremely poor. The Mile High City's skyline was difficult to make out from a 9NEWS camera Saturday afternoon.

Credit: Michael Rhodebeck

CDPHE and the Regional Air Quality Council issued an Action Day Alert for the northern Front Range at 4 p.m. Saturday.

CDPHE said wildfire smoke from California and other western states was to blame. Fine particulate matter concentrations are expected to be in the Unhealthy category throughout the northern Front Range both Saturday and Sunday. Ozone levels are expected to be in the Moderate to Unhealthy for Sensitive Groups range both days.

Denver's air quality has been among the world's worst this week, according to IQAir. On Thursday, a combination of smoke from western wildfires and ground ozone gave Denver the fifth-worst rating in the world.

And yet, people went out to anyway on Saturday. There was still a crowd at Lookout Mountain during the afternoon.

Carlo Gonzalez visited Lookout Mountain for the first time after moving to the state with his girlfriend.

"Love to see this without the smoke," he said. 

The air quality also made a 40-mile bike ride much harder for Dan McDermott and Alden Lowney. 

"You are definitely laboring a lot more. Much tougher to breathe, gasping. Sucks to be honest," said McDermott.

RELATED: Denver in the midst of longest Air Quality Alert streak since at least 2015

RELATED: Denver ranked among the top-5 most-polluted cities in the world Thursday

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