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Holiday revelries and hot, dry weather could combine this weekend to produce unhealthy levels of air pollution in the Salt Lake Valley and other areas, state regulators say.
The most densely populated portions of the state typically see spikes of particulate matter the culprit usually associated with Utah's wintertime inversions on the Fourth of July, according to Bryce Bird, director of the state Division of Air Quality. Last year, for example, air monitors in the Salt Lake Valley recorded concentrations as high as 157 micrograms of PM 2.5 the smaller classification for particulate pollution per cubic meter of air on Independence Day.
The Environmental Protection Agency's standard for PM 2.5 is set at 35 micrograms per cubic meter averaged over 24 hours.
But holiday-related spikes are usually short-lived, said Donna Spangler, a spokeswoman for the Utah Department of Environmental Quality. So they don't always result in violations of the standard, unless weather conditions or other factors prevent the pollution from dissipating.
According to a 2015 study from the National Oceanic and Atmospheric Administration that looked at Ogden and Washington, D.C., as case studies, firework-related particulate concentrations are highest between 9 p.m. and 10 p.m. on July Fourth, and usually dissipate by noon the following day.
Still, short-term exposure can have an impact on health, especially for at-risk populations such as the young, the elderly and those with respiratory conditions such as asthma, Spangler warned. When inhaled, abrasive particulates can become lodged in the lungs and cause irritation or even permanent damage. And ozone, a pollutant that's more common in the summertime and is harmful by itself, can have an additive effect.
"When you have a moderately high level of ozone like we do now, that acts as a double-whammy," she said. "We just want people to be mindful that when you light those individual sparklers or fireworks, there is a health exposure to that."
Brian Moench, president of Utah Physicians for a Healthy Environment, said consumer fireworks can also contain arsenic, lead, mercury, lithium and other toxic compounds, some of which are associated with thyroid disorders, Sudden Infant Death Syndrome and cancers.
Fireworks can also start brushfires, which greatly degrade summer air quality, Moench said.
Moench is concerned that the availability of ever-larger consumer fireworks could exacerbate the problem if state lawmakers do not take action.
"There seems to be a genuine arms race with larger commercial-grade fireworks being launched throughout residential neighborhoods," he said.
Bird said he himself plans to attend some community firework displays, which he noted have less impact on air quality because they reach higher elevations, where pollutants dissipate more quickly. They're also less likely to impact individual health, he said, because they're fired away from the observing crowd.
The biggest health impact, he said, comes from amateur displays, when a family is huddled around smaller fireworks.
Those who do opt for a smaller display should try to stay out of the fireworks' smoke to reduce their exposure, Bird said, and should pay attention to what their body is trying to tell them.
"Trust your body and your senses," he said. "If your body is telling you that the smoke is irritating your eyes, the back of your throat that's probably an indicator that you should remove yourself from that exposure."
There doesn't appear to be a strong correlation between significant respiratory incidents and Fourth of July fireworks, according to the University Hospital Emergency Department, but the U. is working on studies comparing emergency room complaints with air-quality data.
Spangler suggested that those with respiratory conditions should consult their physician to determine whether they should consider staying indoors to avoid exacerbating their symptoms on Independence Day.
As for how long smoke from the fireworks will hang around, it mostly depends on the weather, Bird said. If the weekend brings more warm, sunny weather, air quality could deteriorate. But if Utah manages even a few spotty showers, any smoke generated by holiday fireworks will dissipate.