Pollution exposure in infancy alters gut microbes, may increase disease risk: Study

Exposure to air pollution in the first six months of life impacts a child's gut bacteria in ways that could increase risk of allergies, obesity and diabetes, and even influence brain development, a study has warned.

The research, published recently in the journal Gut Microbes, is the first to show a link between inhaled pollutants -- such as those from traffic, wildfires and industry -- and changes in infant microbial health during this critical window of development.

Previous research by the same group found similar results in young adults.

"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 study author Tanya Alderete, an assistant professor at the University of Colorado Boulder, US.

At birth, an infant hosts little resident bacteria. Over the first two to three years of life, exposure to mother's milk, solid food, antibiotics and other environmental influences shape which microorganisms take hold.

Those microbes, and the metabolites, or byproducts, they produce when they break down food or chemicals in the gut, influence a host of bodily systems that shape appetite, insulin sensitivity, immunity, mood and cognition.

While many are beneficial, some microbiome compositions have been associated with Chrohn's disease, asthma, type 2 diabetes, and other chronic illnesses.

"The microbiome plays a role in nearly every physiological process in the body, and the environment that develops in those first few years of life sticks with you, said first author Maximilian Bailey, a medical student at Stanford University, US.

The researchers obtained fecal samples from 103 healthy, primarily breast-fed Latino infants enrolled in the Southern California Mother's Milk Study and used genetic sequencing to analyse them.

They estimated exposure to PM2.5 and PM10 -- fine inhalable particles from things like factories, wildfires and construction sites -- and Nitrogen Dioxide (NO2), a gas largely emitted from cars.

"Overall, we saw that 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.

For instance, infants with the highest exposure to PM2.5 had 60 per cent less Phascolarctobacterium, a beneficial bacterium known to decrease inflammation, support gastrointestinal health and aid in neurodevelopment, the researchers said.

Those with the highest exposure to PM10 had 85 per cent more of the microorganism Dialister, which is associated with inflammation, they said.

In a previous study, Alderete found that pregnant Latino women exposed to higher levels of air pollution during pregnancy had babies who grew unusually fast in the first month after birth, putting them at risk for obesity and related diseases later in life.

The researchers noted that infants are particularly vulnerable to the health hazards of air pollution because they breathe faster and their gut microbiome is just taking shape.

"This makes early life a critical window where exposure to air pollution may have disproportionately deleterious health effects," they added.