Many moms transition to bottle-feeding at some point, but results of this new study may affect their feeding choices even more.
The study, published in the journal Nature Food, showed that microplastics are released in large quantities when sterilizing plastic baby bottles, pouring hot water to mix formula and shaking the bottles.
Researchers used 10 types of baby bottles and adhered to the guidelines of World Health Organization (WHO) on heating. It stated that powdered formula should be mixed with water heated to at least 70 degrees Celcius (158 degrees Fahrenheit) to reduce bacteria loads.
But, according to the researchers, sterilization and exposure to high water temperatures had the most significant effect on microplastic release. Over a 21-day test period, they found that the bottles released between 1.3 to 16.2 million microplastics per liter.
With this data and the global average breastfeeding rate, the researchers estimated that an average bottle-fed infant could be ingesting 1.5 million microplastics every day during their first year of life.
What are microplastics?
Researchers say this should not alarm parents yet because experts have yet to determine the possible risks posed by microplastics to human health. But that will be hard to do when you're a mom or dad.
Microplastics are tiny fragments of plastic that are too small for the naked eye to see. They are formed when plastic bags, food containers, and even baby bottles are broken down or degraded.
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Thanks to the improper disposal of plastic garbage, microplastics are everywhere. Studies have shown that it's in the ocean, fish, and even in drinking water.
In 2019, a WHO report said there's not enough evidence to conclude that microplastics in drinking water pose a risk to human health. But it also said more research needs to be done to draw a better conclusion. This study says the same thing.
Should you be worried about your baby bottle?
"The last thing we want to do is unduly alarm parents," John Boland, a professor of chemistry and materials science researcher at Trinity College Dublin in Ireland and one of the authors of the study, told NPR. But there is an urgent need to delve deeper into the study.
The baby bottles are made from polypropylene, the most commonly used plastic for food containers. The release of microplastics was relative to high temperatures. Hot water, as well as shaking the bottle to mix formula, make the plastic degrade more, releasing more microplastics. Room-temperature water and shaking the bottle for only a minute causes the release of "hundreds of thousands" of microplastics.
In countries where breastfeeding rates are high, or glass bottles are more popular, it can be said that babies have the lowest potential exposure.
What can you do now?
Boland suggested that parents let the feeding bottle and hot water cool down first before transferring milk or mixing formula. He also warned against warming breast milk or formula using the microwave. It can create "pockets of really superheated water adjacent to the plastic, and that gives rise to copious quantities of microplastics," Boland added.
Experts recommend exclusive breastfeeding until the baby reaches 6 months old, or when he or she starts solid foods. Another way of giving baby expressed breast milk is through a cup. With this news, a switch to glass feeding bottles may be worth considering, too.