Denver air quality exceeded the WHO annual limits on more than one-of third of the days from 2020 to 2021. Due to wildfire smoke from wildfires out west, Denver air quality averaged nearly 3 times the daily recommended limit of dangerous PM2.5 pollutants on its worse day in 2021.
Current Air Quality in Denver
36% Of Days in Denver More Polluted Than WHO Target
Denver’s daily air quality levels exceeded the World Health Organization (WHO) annual limit on 36% of days in 2020-2021. The PM2.5 AQI went beyond the limit on most days in many areas of the city between July and October due to wildfire smoke.

Historical Air Quality Readings for Denver
Is Denver Air Quality Improving?
In the last three years, data shows that air quality in Denver had worsened. 2021 saw a 12% increase in PM2.5 levels while 2020 only saw a 3% increase. Denver’s annual level of air pollution now hovers near the WHO recommended limit.

Why Is the Air Quality Bad Today in Denver?
Weather plays a big role in how the air quality is in Denver each day. The amount of sun can affect how much ozone there is, and wind and rain can affect PM2.5 and particulate air pollution to varying degrees.
Air pollution levels can change quickly, with levels often varying widely throughout the day. Data shows there even appears to be times of the day where air pollution tends to be lower compared to other times.
Below shows how PM2.5 air quality levels around the world tend to vary throughout the day. PM2.5 levels have a tendency to be slightly lower in the afternoon compared to other times of the day. But this is a general trend, Denver PM2.5 AQI levels will not follow this trend every day.

How Wildfires Out West Affect Denver’s Air Pollution Levels
Outside of weather, wildfires are another factor that can significantly affect Denver’s air quality. The worst wildfires typically occur in the months of June to September. Wildfire smoke from California and Oregon can and has travelled all the way to cities as far Denver.

Read More: How Wildfires in California Affect Air Pollution Levels
Below shows how wildfires in September of 2020 affected air quality levels all across the west coast.
Denver Air Pollution: The Negative Health Effects

This analysis of Denver’s air quality is based on PM2.5 pollution. These are particles smaller than 2.5 microns in diameter that can penetrate deep into the lungs and even enter the bloodstream.
Studies have shown that PM2.5 raises blood pressure, inflammation, and rates of heart attacks and strokes.
WATCH: Why Is PM2.5 So Harmful to Us?
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Protect Your Health in Denver From Air Pollution and Wildfire Smoke
Despite the harms of PM2.5 that is in wildfire smoke and air pollution, placebo-controlled studies of air purifiers have found that removing particulate in the home has positive effects on blood pressure, inflammation, and immune response.
Smart Air provides the world’s most cost-effective, data-backed air purifiers to help air-breathers protect themselves and their family. Smart Air is a certified B Corp founded to publicize the simple science behind air purifiers and masks, thereby lowering the cost of breathing clean air.
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