Researchers 'Gobsmacked' by Number of Microplastic Particles in Baby Bottles

Study finds that bottle-fed babies potentially could be ingesting millions of particles every day.

baby uses plastic feeding bottle
A 10-month-old baby uses a plastic feeding bottle.

Tim Clayton - Corbis / Getty Images

If you are a parent, giving your baby formula in a bottle, you might want to consider using a glass one. A new study from Trinity College Dublin has found that baby bottles made of polypropylene release an extraordinary number of microplastic particles. The presence of heated liquid, required to sterilize the bottles and dissolve the powdered formula, makes the microplastic release even worse.

Study co-author John Boland said the team was "absolutely gobsmacked" at the number of particles released. He told the Guardian, "A study last year by the World Health Organization estimated adults would consume between 300 and 600 microplastics a day – our average values were on the order of a million or millions."

Following recommended international sterilization procedures, the team analyzed the potential for release of microplastics in polypropylene bottles, which make up 82% of the market. They estimated the exposure of infants up to 12 months of age in 48 regions of the world, covering three-quarters of the global population, and published their findings in the journal Nature Food.

They found that these bottles release up to 16 million microplastic particles (and trillions of nanoparticles) per liter. At a baby's level of ingestion, this amounts to a daily average of 1.5 million microplastic particles swallowed daily. This number was higher in North American and Europe, where the estimated daily exposure is 2,280,000 and 2,610,000 particles, respectively.

There is a clear connection between the temperature of the water and the release of particles. When the water temperature went from 77 F to 203 F (25 C to 95 C), the number of particles increased from 0.6 million to 55 million per liter. Shaking the bottle to dissolve formula and mix it thoroughly added to this release.

Professor Liwen Xiao, who worked on the study, said in a press release that it's a departure from previous research, which has mostly focused on human exposure to microplastics that have been transferred to water and soil through degradation in the environment:

"Our study indicates that daily use of plastic products is an important source of microplastic release, meaning that the routes of exposure are much closer to us than previously thought. We need to urgently assess the potential risks of microplastics to human health."

Although this discovery is surprising, the researchers do not want parents to panic prematurely. Very little is known about the effect of microplastics on the human body. It's likely most of these are excreted, although further research must be done to determine how much gets absorbed into the bloodstream.

They encourage parents to use glass bottles if possible, and offer suggestions for how to use plastic in a way that minimizes the microplastic release. Boil water in a non-plastic container and let it cool. Use this to rinse bottles three times after sterilization. Make formula in a non-plastic container, cool, and pour into the plastic bottle.

The scientists say this highlights "an urgent need to assess whether exposure to microplastics at these levels poses a risk to infant health." They also plan to investigate technologies that could prevent particle release, such as a hard coating on the polypropylene, and better filtration systems that filter out micro- and nanoplastic particles.