Plastic baby bottles are light-weight and convenient — no wonder they make up more than 80% of the baby bottle market around the world.
But a recent study published in Nature Food found they can expose infants to thousands or even millions of particles of microplastics per day, higher than previously thought.
The big question is if — or how — that could affect a baby’s health.
The simple answer right now is researchers just don’t know, said Dr. Jing Jing Wang, study co-author and a scientist at the AMBER Research Centre and Centre for Research on Adaptive Nanostructures and Nanodevices at Trinity College Dublin in Ireland.
“I don’t think anyone expected the very high levels that we found,” Wang told TODAY in an email.
“Our aim is not to worry parents and we have communicated as strongly as we can that we do not know the potential health risks of infant ingestion of microplastics… this is a new and rapidly evolving area of research and the data on the potential impact on human health is not well developed.”
But based on what’s known about the impact on the health of animals such as mice and fish, including digestive disturbances and brain damage, Wang noted the findings would suggest “we should take steps to remedy” microplastic release.
Microplastics are tiny bits of plastic smaller than a sesame seed, according to the National Oceanic and Atmospheric Administration. They can be harmful to ocean and aquatic life, and have been detected in human stools.
Baby bottles made of polypropylene — the typical type of plastic used in such products — can release microplastics when they are heated or shaken, the new study found. Researchers mimicked the steps parents take to prepare infant formula by following the cleaning, sterilizing and mixing techniques recommended by the World Health Organization. They then measured the amount of microplastic particles in the liquid inside.
The results were striking: Polypropylene infant feeding bottles leaked an average of 4 million microplastic particles per liter, or about a quart, of liquid. Exposure to high temperature water significantly increased the release of plastic bits.
The study estimated the average microplastics exposure level for a bottle-fed baby was more than 1.5 million particles a day, or 2,600 times that of an adult. Infants in North America and Europe consumed even more plastic bits based on the preference for plastic baby bottles in those regions.
The plastics industry said reporting about such small particles can sound alarming, but detecting something does not mean it presents a health risk.
The safety of plastics used in contact with foods, including baby bottles, is “very well regulated” in the U.S. and Canada with the help of expert scientists, the American Chemistry Council’s Plastics Division said in a statement. The U.S. Food and Drug Administration considers temperature changes, such as heating, as part of its regulatory approach to food contact, it noted.
But pediatricians said parents would be right to be alarmed by the study findings.
“The science is still just scratching the surface of the concerns there. But when you see microplastics, you know the plastic is breaking down and the deeper concern is actually the less visible concern,” said Dr. Leonardo Trasande, a pediatrics professor at NYU Grossman School of Medicine and director of the Center for the Investigation of Environmental Hazards at NYU Langone in New York City.
“It’s the chemical molecules that break down from polymers.”
Chemicals that absorb into foods from plastics and are of particular concern include phthalates, which can disrupt metabolism and reduce the male sex hormone testosterone; and bisphenols like BPA, which is essentially a synthetic estrogen and can make fat cells bigger, said Trasande, who was the lead author of the American Academy of Pediatrics’ policy statement on food additives and child health.
Researchers know much less about microplastics, which may not be absorbing directly into the human body in the same way that such chemicals do, he noted.
“I do think parents should worry about this,” added Dr. Claire McCarthy, a pediatrician at Boston Children's Hospital and an assistant professor of pediatrics at Harvard Medical School.
“The problem is we don’t know how much they should worry… We don’t know exactly how much exposure causes harm, or what factors might increase or decrease the harm. But it’s fair to say that we should all be using less plastic, especially when it comes to feeding our babies and children.”
Advice to parents
To lower the amount of plastic bits a baby consumes, the authors of the new study advised shaking and heating the plastic bottle as little as possible. Wang said the four main steps to do that are:
- Rinse sterilized feeding bottles with cool sterile water to wash away some of the microplastics that might have leached out.
- Always prepare formula in a non-plastic container.
- After it has cooled to room temperature, transfer the formula into the cooled, sterilized feeding bottle.
- Avoid rewarming prepared formula in plastic containers, especially in a microwave oven, which can generate "micropockets" of superheated liquid.
The simpler solution is to switch to switch to glass, Trasande said. The vast majority of containers in his household are made of glass and he used glass when his two children were babies.
Both Trasande and McCarthy advised parents to avoid using plastic baby bottles in general, or to use them less. Besides glass, stainless steel is also an option.
If sticking with plastic, parents should hand-wash bottles rather than putting them in the dishwasher, McCarthy advised. Machine washing with harsh chemicals at high temperatures can produce wear and tear that helps break down the plastic polymers.
“As for heating the formula or breast milk, parents shouldn’t do it in anything plastic,” she said.
“They could heat it in a pan — preferably not a non-stick one, as those have chemicals too — or in glass. Babies don’t necessarily need formula or breast milk to be warm; this could be a good reason to get them used to drinking it cool or at room temperature.”