Inversion 01

A haze is seen over Weber County on Tuesday, Dec. 3, 2019. Poor air quality is expected through the rest of the week.

Gov. Gary Herbert’s recommendation that Utahns avoid unnecessary travel, as well as stay-at-home orders issued by three Utah counties, have led to significant reductions in traffic volume along the Wasatch Front, which in turn has led to reductions in emissions.

According to John Gleason, spokesperson of the Utah Department of Transportation, or UDOT, Interstate 15 in Salt Lake and Davis counties, as well as at the Point of the Mountain area, has had consistently less traffic than normal for the past three weeks.

“In general terms, on any given day we’re seeing a traffic reduction of about 35% to 50% of normal traffic volume on our main roads,” Gleason said.

Both Salt Lake and Davis counties have issued mandatory stay-at-home orders that close nonessential businesses and prohibit public and private gatherings of anyone who isn’t part of the same household. Wasatch County has a similar order in place.

On March 26, Herbert issued a Stay Safe, Stay Home directive encouraging all Utahns to “stay home as much as possible” and “limit travel only to essential travel,” but emphasized that “these directives are not to be confused with a shelter-in-place.”

Gleason said UDOT expected to continue seeing reductions in traffic in the upcoming weeks.

“As long as people are staying at home, which is what our leaders have requested, we’re expecting to see fewer numbers of vehicles on the road,” said Gleason. “And so it’s encouraging that you are seeing so many people, so many Utahns that are taking this seriously and taking the advice of staying home.”

Utah Department of Environmental Quality spokesperson Jared Mendenhall said it isn’t yet clear what impact decreased traffic volume will have on air quality in the state.

“Intuitively, we know there are fewer emissions (when traffic decreases),” Mendenhall said. “However, springtime has great air quality in the state of Utah. And (so it is difficult) to be able to pinpoint exactly how much that reduction has caused in ground-level particulate matter.”

Air quality in Utah is so bad during winter months because of inversions that trap particulate matter in the Salt Lake and Utah valleys, Mendenhall said. And with no inversions in the springtime, there’s no way to measure the impact less traffic has on air quality.

“The issue that we have is none of that (particulate matter) is being trapped near the ground,” he said. “And so you can’t measure it.”

However, if stay-at-home orders and directives continue into the summer months, Mendenhall said “there’s probably going to be some opportunities to measure reductions in ozone.”

Automobiles make up about 40%-50% of the pollution that builds up during Utah’s inversion season, according to Mendenhall. He added that Utahns could decrease their carbon footprint by continuing to drive less even after the pandemic passes.

“This is tough. People are dying. This is a bad situation,” said Mendenhall. “And so we certainly don’t want to be trite about it. But while we’re … dealing with this, perhaps people can take a look at options like teleworking, they can see how it can work for their current position, and maybe incorporate some of those things when next winter comes around and there’s one of these inversions.”

If not, Mendenhall said, Utah will continue to have poor air quality in the winter months.

“If we’re just doing this in the spring time and when next winter comes around we’re all back to the same habits that we had, we’re not going to see an impact on the ground-level air quality that we’re typically concerned with here in (the) Salt Lake area,” Mendenhall said.

Economic disruption caused by the COVID-19 pandemic may have an impact on global pollution levels.

Marshall Burke, an assistant professor in Stanford University’s Department of Earth System Science, wrote in a blog post that “the reductions in air pollution in China caused by this economic disruption likely saved 20 times more lives in China than have currently been lost directly due to infection with the virus in that country.”

Burke continued that his calculations do not support “any idea that pandemics are good for health.”

“The effects I calculate just represent health benefits from the air pollution changes wrought by the economic disruption, and do not account for the many other short- or long-term negative consequences of this disruption on health or other outcomes,” said Burke, adding that “these harms likely vastly exceed any health benefits from reduced air pollution.”

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