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How best to compare cities with worst air: Big data or government metrics?

denver air quality Aug. 6.jpg
Posted at 3:07 PM, Aug 23, 2021
and last updated 2021-08-23 17:07:59-04

Colorado health officials say they cannot vouch for the accuracy of the increasingly popular private air quality apps that recently ranked metro Denver as the worst in the world. Instead, they suggest people rely on government-run metrics.

The Colorado Department of Public Health and Environment officials say apps like the one from IQAir, a Swiss air filter manufacturer, give only momentary readings that can be a misleading basis for rankings. They also use equipment that isn’t uniformly calibrated and data that isn’t always verified.

Air quality in a particular area can vary considerably over time and, because of this, it’s not surprising that the air quality in Denver may be worse than in heavily polluted cities temporarily at any given point in time,” Colorado Air Pollution Control Division director Garry Kaufman said. “It’s problematic to draw comparisons between air quality in Denver and these other places without looking at pollution levels over much longer periods.”

If you’re concerned about air quality, state officials recommend checking CDPHE-vetted information from 16 measuring stations via or tracking readings on the U.S. Environmental Protection Agency’s site — — which includes data collected at embassies worldwide and allows international comparisons.

Nobody’s disputing that the unhealthy air quality in Colorado Front Range cities has deteriorated over the past two years. This summer, health officials have issued a record 57 air quality advisories, one every day since July 4th except for Aug. 15 and Aug. 19.

Read the full story in The Denver Post.