SALT LAKE CITY — The largest study of its kind tracked more than 100,000 Utah patients and found even a slight uptick in fine particulate pollution triggers childhood lung infections.

Researchers at the University of Utah, Intermountain Healthcare and Brigham Young University spent 15 years studying 146,397 individuals treated for acute lower respiratory infection along the Wasatch Front.

“The most important finding of this study is that infectious processes of respiratory disease may be influenced by particulate matter pollution at various levels,” said lead author Dr. Benjamin Horne, director of cardiovascular and genetic epidemiology at the Intermountain Medical Center Heart Institute in Murray. “The exact biological implications of the study’s findings require further investigation.”

The study was published in the American Journal of Respiratory and Critical Care Medicine Friday.

Researchers used estimates of fine particulate pollution data from air quality monitors along the Wasatch Front, where 80 percent of Utah's population lives. Short-term periods of elevated PM2.5 pollution levels were matched with the timing of increases in health care visits for acute lower respiratory infection.

Grid View With the Wasatch Mountains to the left, a layer of haze and smog covers the Salt Lake Valley on Wednesday, Dec. 13, 2017. Stuart Johnson, Deseret News

Looking north from Salt Lake City, a layer of haze and fog surrounds Ensign Peak as the inversion camps out over the area on Wednesday, Dec. 13, 2017. Stuart Johnson, Deseret News

Looking south across the Salt Lake Valley, Lake Mountain in Utah County pops out of the haze and fog on Wednesday, Dec. 13, 2017. Stuart Johnson, Deseret News

A layer of haze and smog obscures the Salt Lake Valley on Wednesday, Dec. 13, 2017. Stuart Johnson, Deseret News

The Oquirrh Mountains poke out of a layer of haze and smog covering the Salt Lake Valley on Wednesday, Dec. 13, 2017. Stuart Johnson, Deseret News

The layer of fog and smog thins out near the mouth of Parleys Canyon on Wednesday, Dec. 13, 2017. Stuart Johnson, Deseret News

The Oquirrh Mountains poke out of a layer of haze and smog covering the Salt Lake Valley on Wednesday, Dec. 13, 2017. Stuart Johnson, Deseret News

Part of Ensign Peak, at right foreground, pops up above the a layer of fog and smog as an inversion camps out over the Salt Lake Valley on Wednesday, Dec. 13, 2017. In the distance at left is Antelope Island. Stuart Johnson, Deseret News

Ensign Peak pops up above the a layer of fog and smog as an inversion camps out over the Salt Lake Valley on Wednesday, Dec. 13, 2017. In the distance at left is Antelope Island. Stuart Johnson, Deseret News

The findings were culled from visits involving 146,397 patients between 1999 and 2017.

“Overall, it took about two to three weeks for the (acute respiratory infection) hospitalizations or clinic visits to occur in this study after the rapid rise in PM2.5 had been observed,” Horne said.

Bronchiolitis, a condition in which small breathing tubes in the lungs called bronchioles become infected and clogged with mucus, is the most common acute lower respiratory infection in children.

Between 50 percent to 90 percent of those bronchiolitis cases are caused by the respiratory syncytial virus, or RSV, which is the most common cause of hospitalization during the first two years of life.

In an analysis of death rates among the study population, 17 children ages 0-2, nine children ages 3-17 and 81 adults died within 30 days of diagnosis with acute lower respiratory infection.

Horne said it is possible the pollution makes the human body more susceptible to infection or compromise one's ability to fight off infection.

"It may be that PM2.5 causes damage to the airway so that a virus can successfully cause an infection or that PM2.5 impairs the immune response so that the body mounts a less effective response in fighting off the infection," he said.

Acute increases in pollution, too, may lead people to stay indoors where they are in closer contact with people already infected, he said.

The study involving Wasatch Front residents played out in a location that does not have as high as levels of PM2.5 as places like Los Angeles or New York. Utah, however, does experience significant spikes in pollution levels when inversions set up and trap pollutants on the valley floor.

Horne said it is not clear how the study's findings might translate for those regions where people are exposed to higher levels of pollution on a more prolonged basis.

“It may be, though, that long-term exposure to air pollution makes people more susceptible to (acute lower respiratory infections) on a routine basis, although additional studies will be required to test this hypothesis.”

Denni Cawley, executive director of Utah Physicians for a Healthy Environment, said research involving air pollution and children's vulnerability needs to be taken seriously.

"National research has shown even low levels of pollution that are below federal standards has an effect," she said. "A local study like this can show how children, especially, are impacted."

An estimated 60 percent of U.S. children, according to researchers, live in counties with air pollution levels that exceed the federal standard.