SALT LAKE CITY — In Utah, there are two big holidays where people celebrate with fireworks: the Fourth of July and Pioneer Day on July 24.
From the big city-sponsored shows, to the neighborhood kids shooting off the fountains they bought at the local fireworks stand, the booms and whistles and other noises make for a good time.
But they also make for some bad air.
Fireworks produce a lot of smoke and ash, spewing tiny particulates known as PM 2.5 into the air — the same stuff found during wintertime inversions.
"There are rules of thumb: If you can see the smoke and smell the smoke, you're probably getting some impact from that,” said Bryce Bird, air quality director at the Department of Environmental Quality.
The DEQ monitors the air 365 days a year, but on the evenings of July 4 and July 24, the air quality monitors show big changes.
“We see very high concentrations during those few hours in the evening when, after the sun goes down … the fireworks are most visible,” Bird said. “We see that very pronounced spike from maybe 9:30 to 11 p.m. on those holidays."
Bird said there are elevations of PM 2.5 during the three days before and the three days after the holiday — which is when fireworks can be discharged — but certainly the highest levels are on the actual holidays.
The good news is the pollution levels quickly return to normal as the winds disperse the smoke.
It turns out that the smaller neighborhood fireworks displays are often worse than the big city-sponsored shows.
“On the neighborhood level when we get tens, hundreds, perhaps even thousands of people enjoying these fireworks, the particles produced from the combustion do concentrate in those areas,” Bird said, “and so we see some elevated levels that are above the levels that are considered safe under the health standards."
On average the 24-hour standard for PM 2.5 is about 35 micrograms per cubic meter. Last year in the Salt Lake Valley the levels jumped to 157 micrograms when the fireworks were in use.
For those with chronic breathing issues, staying indoors will limit the exposure to these particulates. If people want to be outside watching the fireworks, know which way the wind blowing.
"Don't park grandma in the lawn chair in the path of the smoke, as well as the children, just keep that in mind if you can avoid exposure,” Bird said.
Contributing: Viviane Vo-Duc
Email: kmccord@deseretnews.com