Chlorinated water doesn’t disrupt kids’ gut bacteria

By keeping the bad bugs out of the water supply, chlorination is allowing kids' microbiomes to thrive and do their good work maintaining health. (Credit: Water Alternatives/Flickr)

Using chlorine to treat drinking water in Dhaka, Bangladesh didn’t disrupt the normal population of bacteria in the digestive tract of children, research finds.

The addition of the chlorine also reduced diarrhea and antibiotic use, according to the study in Nature Microbiology.

More than 2,000 children die every day around the world simply because they lack clean drinking water, according to the US Centers for Disease Control.

Engineers have devised simple, low-cost ways to purify drinking water in low-income countries using chlorine, but a common concern is that adding chlorine to water could harm the beneficial bacteria in children’s developing gut microbiomes, which play an important role in keeping health intact.

The children’s microbiomes—tested from stool samples collected one year after the dispensers were installed—had a similar diversity and abundance of bacteria as children who didn’t receive chlorinated water. Some slight differences were observed, including the enrichment of beneficial bugs and increases in the presence of some antibiotic resistance genes, but those changes were small and the overall make-up of their microbiomes was similar.

While chlorine inactivates microorganisms present in water during storage, transport, and delivery through the tap, this study suggests that it’s not killing the good bacteria after the chlorinated water is consumed. In fact, by keeping the bad bugs out of the water supply, chlorination is allowing kids’ microbiomes to thrive and do their good work maintaining health.

That’s very important especially in the first few years of life. The gut microbiome of infants is seeded at birth, then grows and stabilizes to its adult-like state by the time a child is about three years old. The progressive colonization by different bacteria in the microbiome may be important to several developmental milestones related to metabolism and weight maintenance, allergy development, disease susceptibility, and even mental health.

“No doubt further studies may be helpful for understanding all the long-term health effects of drinking chlorinated water,” says Maya Nadimpalli, research assistant professor in civil and environmental engineering at Tufts University, “but this study makes it clear that the microbiome is protected after at least one year of exposure, so that the benefits of water chlorination—which can save hundreds of thousands of lives each year—continue to outweigh diminishing concerns about its safety.”

Amy Pickering, formerly of Tufts and now chair in global poverty and practice at the University of California, Berkeley, has been working on developing and field testing automated chlorination devices that are compatible with water infrastructure in Africa and Asia.

“It’s very encouraging that such a widely used and low-cost water treatment method doesn’t harm children’s developing microbiomes,” says Pickering, who led the original trial and this study’s research team.

Nadimpalli, whose research takes place in collaboration with the Stuart B. Levy Center for Integrated Management of Antimicrobial Resistance at Tufts, notes that since children in Bangladesh are frequently exposed to pathogens, they are also treated with antibiotics at a rate five times higher than children in the US.

“The treatments themselves have a harmful effect on diversity in the gut microbiome, and you end up with worse health outcomes and potentially more antibiotic-resistant pathogens,” she says. “So chlorination can help reduce incidence of disease, limit use of antibiotics, and still keep microbiomes healthy.”

Researchers from the International Centre for Diarrheal Disease Research in Bangladesh and Eawag in Switzerland also contributed to the work.

Source: Tufts University