When Fourth of July fireworks burst this weekend, they’ll contribute to Colorado’s already poor air quality, adding smoke, soot and toxic chemicals to a sky fouled by wildfire smoke.
Air pollution from wildfires burning across the state and the Front Range’s typical summer ground-level ozone problem will be intensified, experts say, as cities, sports teams and families launch pyrotechnics over the long holiday weekend.
The warns that breathing the fine particulate matter and chemicals released by exploding fireworks can exacerbate symptoms for people who suffer from asthma or chronic obstructive pulmonary disease.
“Itap a time for fun, right? We want people to enjoy themselves and have fun,” said Nick Torres, the lung association’s advocacy director in Colorado. “But fireworks are a contributor to poor air quality.”
Some Colorado cities and counties, including Colorado Springs, Pueblo and Highlands Ranch, have canceled this weekend’s fireworks shows as wildfires rage, and cities such as Denver have replaced them with drone shows because of the high fire risk.
Many cities have prohibited individuals from shooting them off themselves, although those bans are often ignored and loosely enforced. And those smaller backyard fireworks can be just as damaging to air quality.
When fireworks explode, they emit fine airborne particles that can be inhaled and enter the bloodstream. Along with particulate matter, known as PM2.5, fireworks also release chemicals that are used to create loud noises and vivid colors. Gases and heavy metals can hang for hours after the brilliant plumes of red, white and blue have faded.
Gases from fireworks include sulfur dioxide, carbon dioxide, carbon monoxide and nitrogen oxide, and the heavy metals include barium, copper, cadmium and aluminum.
A massive Fourth of July fireworks display planned for the National Mall in Washington, D.C., will involve 850,000 fireworks in a 40-minute show and will create unhealthy conditions in the nation’s capital, , which obtained internal documents from the .
A park service analysis of the anticipated air quality impacts from that fireworks display determined it will cause “very unhealthy” conditions and stated that people should avoid prolonged exposure around the Mall and central D.C., the newspaper reported.
A 2015 study in the scientific journal found that concentrations of fine particulate matter were elevated on the evening of July 4 and the morning of July 5 at 315 monitoring sites in the United States. On average nationally, particulate matter levels rose 42% during the 24 hours surrounding the holiday, and a site adjacent to a fireworks show can have particulate matter levels three times higher than normal.
In Colorado, a team of meteorologists who track weather patterns in Boulder determined that the city’s 2019 decision to cancel its annual July 4 fireworks show at Folsom Field led to lower air pollution levels on the holiday compared to neighboring cities that shot off fireworks, according to the report. The city has not held a fireworks show since.
The meteorologists monitored air quality indexes for Boulder, Longmont, Broomfield and Denver and found that while Boulder had a slight uptick in air pollution around July 4, the other cities more than doubled their levels. They accounted for weather patterns in each city, the BoulderCast report stated.
An below 50 is considered good. In 2025, Boulder’s air quality index for PM2.5 peaked at 70, largely due to residents who bought fireworks in Wyoming and shot them in their backyards. The index level dropped around 1 a.m.
“Particulates remaining in the air until 1 a.m. would suggest people continued to launch fireworks well into the night, or could be some influence from the topography of Boulder Valley slowing the clear out,” the report said.
Meanwhile, Longmont’s air quality index peaked between 120 and 170 around 10 p.m. when the city’s fireworks show ended. Air quality levels dropped to normal by 11 p.m. Broomfield’s air monitoring stations showed peaks of 140 between 9:30 p.m. and 10 p.m., when that city’s fireworks show took place, and air quality levels returned to regular levels by midnight.
In Denver, fireworks set off by residents likely caused high air pollution levels because the only large-scale display in the city was a 15-minute show hosted by the Colorado Rockies at Coors Field. But the city’s air quality monitors showed a rise in particulates between 9 p.m. and 1 a.m., with sites averaging a peak of 145, BoulderCast reported.
“This suggests that citizen fireworks, and the air blowing in from upstream cities, polluted Denver substantially for several hours,” the report stated.
Ben Castellani, a BoulderCast co-founder and lead meteorologist, said he expects the air quality indexes to peak even higher this year because wildfire smoke has already elevated those numbers at monitoring stations across the Front Range.
“This year I will expect it to be worse of a peak, but not stick around any longer,” Castellani said.
Experts said the pollution from fireworks does not cause long-term health effects because the celebrations are short-lived. But the brief, intense emissions can make some people sick.
“Itap not that great of a danger, but some of the chemicals and metals in fireworks are more dangerous than what’s in the wildfire smoke,” Castellani said.
On Thursday, the issued health advisories for much of the state because of the smoke. The health department warned that people who suffer from respiratory or heart diseases, along with the very young and elderly, should stay indoors. Those advisories are in effect at least until 9 a.m. Friday.
Those advisories are expected to continue through the weekend as hot, stagnant weather sets in, said Mike Silverstein, executive director of the , which helps establish policy to reduce the region’s air pollution.
The air quality council is predicting a because of the hot weather.
“Fireworks is another emissions category just like vehicles or industrial emissions,” Silverstein said. “It just exacerbates our air pollution problem.”
The nine-county Front Range region violates federal air quality standards, leading the to impose tighter regulations, including a requirement that motorists buy a more expensive blend of gasoline that burns cleaner.
The region struggles with ground-level ozone pollution, which is most problematic during the hot months between mid-May and early September. Volatile organic compounds and nitrogen oxides — chemicals released by burning fossil fuels — cook in the sun, forming a blanket that traps heat along the Front Range.
Adding fireworks to the wildfire smoke and the ground-level ozone can make for a dirty, unhealthy holiday.
Torres recommends that people who suffer from lung diseases stay downwind of fireworks displays or watch them inside through windows or via television broadcasts.
“Stay indoors and curl up with your pets, who probably aren’t enjoying fireworks either,” he said.
