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Interstate 70 traffic seen on Thursday, April 21, 2022, near Denver. (Hugh Carey, The Colorado Sun)

The healthy gut “microbiome” of babies living in high pollution areas is under threat from particulates from vehicles, industrial smokestacks and wildfire smoke, leaving them more vulnerable to immune afflictions like diabetes or allergies, a new University of Colorado study says

The findings from babies involved in a mother’s milk study in Southern California go straight to the heart of a series of environmental justice and air pollution laws passed in Colorado in recent years. State lawmakers and regulators are targeting pollution concentrated in lower-income and minority neighborhoods, and overhauling permitting and transportation spending to combat what they have called historic injustice.

The researchers say the study published in the August edition of the science journal “Gut Microbes,” is “the first to show a link between inhaled pollutants … and changes in infant microbial health during this critical window of development.”

The new CU study bolsters previous research about the health impacts of air pollution on adults, said Juan Madrid, a clean air and transportation advocate with Colorado GreenLatinos. Half of Adams County births in 2020-21, and a third of Denver births, were to Latino mothers, Madrid noted. 

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“So the results of this study are alarming, as we know that many Latinos live in disproportionately impacted communities in Adams County and north Denver,” he said. 

Antipollution activists often target south Adams County and north Denver because of the Suncor oil refinery, the Cherokee Generating Station, multiple interstates jammed with truck traffic, numerous heavy industries and a history of metals smelting. 

“This study adds to a growing body of evidence that breathing pollution harms more than just our lungs,” said Laurie Anderson, Colorado field organizer for Moms Clean Air Force. “Babies and children are especially vulnerable. Here in Colorado, where we have persistent air pollution problems, this study increases the urgency of taking swift action to reduce pollution — especially in the most impacted communities.”

The infant gut collection of microbes is largely a blank slate until influenced by breast milk, solid food, the environment, any medicine intake, and other factors, according to the CU researchers. Beneficial microbes work to build appetite, immunity, insulin control and brain functions. But “bad” microbes can influence asthma, Type 2 diabetes and other lifelong issues. 

PM2.5 particle pollution is limited by regulations, and each particle is about 1/70th the diameter of a human hair. The particles are emitted by car and truck fossil fuel exhaust, coal-fired power plants or chemical emissions from factories, burning forests and other sources. Colorado is not currently in violation of EPA limits on PM2.5 in the way that it violates ozone caps. 

But decades of regulation are just starting to have an impact, and low income neighborhoods near refineries, power plants and busy highways are much more exposed than others. Bad wildfire seasons like those in 2020 and 2021 wipe out a lot of progress. 

The research also looked at markers from slightly larger particles, PM10, and nitrogen dioxide, primarily a vehicle-related emission.

The results speak to a crucial age of development where the environment “sticks with you,” the CU researchers say. They talked about the study in a week of record heat in Denver and much of Colorado, and where state officials called another series of Ozone Action Day Alerts cautioning those in urban areas vulnerable to some forms of air pollution.

“I want to be able to arm individuals and communities with the information needed to fight for change,” said Tanya Alderete, study co-author and assistant professor of integrative physiology at the University of Colorado.

The CU study piggybacked on a mother’s milk study by genetically analyzing fecal samples from 103 primarily Latino infants in Los Angeles. Alderete learned of the cohort and was able to gain access to the genetic data while she worked on her Ph.D. at the University of Southern California. The infants’ health data was overlaid with hourly pollution samples in their area that are taken constantly by the EPA. 

Those exposed to the most PM2.5 lost 60% of a bacterium that decreases inflammation and aids infant brain development. Those exposed to the most PM10, slightly larger particles, had 85% more of a bacterium associated with inflammation. 

A comparison of the relative sizes of the pollution most Coloradans worry about. Note that anything PM2.5 or smaller can’t be seen by the human eye. (Environmental Protection Agency guide to home air filters)

Alderete’s earlier research on air pollution and microbes looked at about 50 young adults, showing that air pollution exposure from nearby high-traffic roads “was associated with bacteria in the gut,” she said. “And those bacteria had been linked with obesity, Type 2 diabetes and insulin sensitivity.” 

Those results, Alderete said, have since been replicated in a larger sample of young adults. 

The researchers have also received funding and approval to follow the Southern California babies through six years, to check on the long-term impacts of their gut biome findings. 

“We’re going to also be considering individual behavioral factors as well as the environment,” Alderete said. “If there is this association with air pollution and the gut bacteria, how long does that persist? Do we see that over the course of development and the question is what kind of health implications does that have?”

The study is not able to distinguish the varied influence of the child’s indoor environment on the same intestinal biome issues. Home cooking creates particulates that can influence personal health, as well as other behavioral or environmental factors such as burning candles or having access to home air filtration. 

In the meantime, the researchers say all families should take the easiest precautions against local air pollution: avoid exercising near traffic or industrial areas, open windows or use stove vents during home cooking that may create particulates, and seek a low-cost air filtration system. As always, they emphasize that moms should continue breastfeeding as long as possible, one of the most crucial ways to support a healthy baby biome and brain development. 

“What we do know is that breastfeeding can act as a very potent beneficial probiotic,” Alderete said.

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Michael Booth

Michael Booth is a Colorado Sun reporter covering health, health policy and the environment. Email: booth@coloradosun.com Twitter: