Being exposed to high levels of air pollution during the first six months of life can impact infants’ gut microbiota, increasing their risk of allergies, obesity, diabetes and even influencing brain development, suggests a new study by researchers from the University of Colorado Boulder.

This is the first study to look at the relationship between air pollution and babies’ developing gut microbiota and show a link between the pollutants inhaled, such as all those generated by traffic or industry, and changes in the gut microbiome during early life. The results were published in Gut Microbes.

“This study adds to the growing body of literature showing that air pollution exposure, even during infancy, may alter the gut microbiome, with important implications for growth and development,” said senior author Tanya Alderete, professor at CU Boulder, in a press statement.

Researchers found significant associations between the levels of exposure to air pollutants and gut microbiota composition. Infants exposed to pollution had bacteria in their gut linked to inflammatory and metabolic diseases

In fact, previous research by the same group from 2020 showed a direct link between air pollutants and changes in young adults from Southern California. Now, they have focused on infants and early life, as children are particularly vulnerable to pollution as they breathe faster and they are at a time in life when their gut microbiota is being formed.

In this experiment, researchers analyzed fecal samples from 103 healthy, primarily breastfed Latino infants enrolled in the Southern California Mother’s Milk Study. To calculate individual exposure to air pollution, they used data from the U.S. Environmental Protection Agency that monitors hourly air quality. Thus, they were able to estimate exposure to inhalable fine particles such as PM2.5 and PM10, and NO2, largely coming from traffic, factories, wildfires, and construction sites.

Researchers found significant associations between the levels of exposure to air pollutants and gut microbiota composition. Infants exposed to pollution had bacteria in their gut linked to inflammatory and metabolic diseases. Moreover, babies with the highest level of exposure to PM2.5 particles had 60% less of a bacterium related to a beneficial gut health impact, whereas babies who were most exposed to PM10 particles had 85% more of Dialister, a microbe linked to systemic inflammation, cancer, multiple sclerosis, and mental health problems in adults.

“Ambient air pollution exposure was associated with a more inflammatory gut-microbial profile, which may contribute to a whole host of future adverse health outcomes,” said Alderete.

Even so, the authors highlight that they have found associations and not a cause-effect link. More studies need to be done to gain a profound insight into the mechanisms by which pollution may cause changes to an infant’s gut microbiota and whether those changes have any lasting consequences for an infant’s health throughout their life.

What is clear, according to the authors, is that early life is a critical window and air pollution exposure can have a disproportionate, deleterious impact on health.

“This is a pioneering study in examining the relationship between gut microbiota and environmental exposure in babies in the first 6 months of life, but it still very preliminary,” assesses Professor Mari Carmen Collado from the Institute of Agrochemistry and Food Technology at the Spanish National Research Council (IATA-CSIC), who is an expert on gut microbiota and early life and who did not take part in the study.

According to Collado, it is worth highlighting that exposure to PM2.5 alters the gut composition of Bifidobacteria and Bacteroidetes, “which is really important as we know they are the gold standards in infants’ microbiomes, associated with benefits for health.” Also, Collado suggests, “It would be interesting, for instance, to evaluate the impact of air pollution on the gut-brain axis, to see whether it has an effect on babies’ neurodevelopment.”

The authors of the study advise breastfeeding as long time as possible as a way of developing a healthy microbiome in infants, which, according to Alderete, may help offset some of the adverse effects of exposure to environmental pollution.




Bailey MJ, Holzhausen EA, Morgan ZEM, Naik N, Shaffer JP, Liang D, Chang HH, Sarnat J, Sun S, Berger PK, Schmidt KA, Lurmann F, Goran MI, Alderete TL. Postnatal exposure to ambient air pollutants is associated with the composition of the infant gut microbiota at 6-months of age. Gut Microbes. 2022 Jan-Dec;14(1):2105096. doi: 10.1080/19490976.2022.2105096