New US research has found a link between pollution causing fine particulate matter, also known as PM2.5, and an increased risk of acute lower respiratory infection (ALRI) in young children.

Carried out by researchers from Intermountain Healthcare, Brigham Young University and University of Utah, the groundbreaking new study is the largest to date to look at a possible link between PM2.5 and ALRI, following 146,397 individuals over a 17-year period.

Participants were all treated for ALRI between 1999 and 2016 at Intermountain Healthcare facilities located throughout Utah’s Wasatch Front region. PM2.5 levels were estimated based on data taken from air quality monitoring stations in the same area, which is home to around 80 percent of Utah’s population.

The researchers found that elevated levels of PM2.5 were associated with an increased risk of developing ALRI for both adults and children, including newborns and toddlers up to age two, who represented 77 percent (112,467) of those who had an ALRI diagnosis.

Increases in PM2.5 levels also led to increased doctor visits for these lung infections.

“Overall, it took about 2-3 weeks for the ALRI hospitalizations or clinic visits to occur in this study after the rapid rise in PM2.5 had been observed,” added lead author Benjamin Horne.

Seventeen children ages 0-2, 9 children ages 3-17 and 81 adults also died within 30 days of diagnosis with ALRI.

PM2.5 is defined as air pollution particles measuring 2.5 micrometers or smaller. By comparison, a human hair is between 50 and 70 micrometers thick.

Motor vehicles contribute about 48 percent of emissions that lead to the formation of these fine particulates, small industry and businesses such as gas stations and dry cleaners, as well as home heating, contribute about 39 percent, and large manufacturing accounts for 13 percent.

Nearly 60 percent of US children live in counties with PM2.5 concentrations above air quality standards, although the average daily PM2.5 level is lower in Utah than in places like Los Angeles and New York.

However, air pollution may become trapped in the high mountain valleys of the Wasatch Front, which often leads to sharp increases in PM2.5 to levels considered to be unhealthy (>35 micrograms per cubic meter, and at times approaching 100 ug/m3).

“In many places that have higher average PM2.5, the PM2.5 level does not vary as much as it does on the Wasatch Front, so it is not clear how this study’s findings may transfer to those locales where the air pollution exposure is higher over the long term but short term spikes do not occur,” said Dr. Horne. “It may be, though, that long-term exposure to air pollution makes people more susceptible to ALRI on a routine basis, although additional studies will be required to test this hypothesis.”

Dr. Horne added that when a sharp increase in the level of PM2.5 does occurs, people may be able to prevent infections or decrease the severity and duration of ALRI symptoms by reducing their exposure to the air pollution, not touching their face with dirty hands, and washing their hands often to reduce infection risk.