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Plastic Baby Bottles Shed Millions of Particles of Microplastics, Study Finds

close up of baby drinking from a bottle

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Key Takeaways

  • Polypropylene is used in most plastic baby bottles on the market today.
  • A recent study found that baby bottles made with polypropylene plastic shed millions of particles of microplastics, which babies are ingesting.
  • Preparing formula in a non-plastic container when transferring it to plastic baby bottles once cooled is a way to reduce your baby's exposure to microplastics.
  • Scientists don't yet know the impact microplastics have on human health.

Since the 2012 ban on the use of BPA in baby bottles, many bottle makers turned to polypropylene—a sturdy, BPA-free plastic—for their bottles. For years, this seemed an ideal solution—less expensive and cumbersome than glass bottles, but safe from chemicals that could leach into babies’ developing bodies. Today, an estimated 82% of all plastic baby bottles manufactured around the world contain polypropylene.

Unfortunately, a recent study published in the journal Nature Food found that polypropylene baby bottles might in fact be releasing upwards of 16 million particles of microplastics per liter into your baby's formula. But there's no need to panic, the study also offered recommendations for how to safely sanitize bottles and warm your baby's formula without risking exposure to harmful microplastics.

Study Findings and Conflicting Recommendations

The study explains, “Polypropylene-based products are commonly used for food preparation and storage, but their capacity to release microplastics is poorly understood. Studies showed that [polypropylene infant bottle] sterilization and exposure to high-temperature water significantly increase microplastic release.”

That’s difficult news for parents since both practices are currently recommended by top health organizations when using plastic bottles: current Centers for Disease Control (CDC) guidelines encourage the boiling of plastic infant feeding bottles for five minutes daily to ensure “extra germ removal.” 

And the World Health Organization (WHO) recommends using water at a temperature of no less than 70 degrees Celsius (158 degrees Fahrenheit) for formula preparation since formula is not a sterile substance. That guidance is in direct opposition to new findings set forth in this groundbreaking study that says, “exposure to high-temperature water significantly increases microplastic release (from 0.6 million to 55 million particles per liter) when the temperature increases [from 77 to 203 degrees Fahrenheit].”

Jing Jing Wang, PhD

When we shake this hot liquid, it increases the numbers of particles that flake off the microplastic. It happens because of the structure of polypropylene, and the way that the plastics are manufactured.

— Jing Jing Wang, PhD

The team of scientists involved in the study admit that further research is needed in order to determine the exact mechanism of microplastic release. “Hot liquids cause the inner surface of plastic bottles to ‘flake off’, like tiny particles, becoming detached and ending up in the liquid," says Jing Jing Wang, PhD, a researcher at Trinity College Dublin says. "Also, when we shake this hot liquid, it increases the numbers of particles that flake off the microplastic. It happens because of the structure of polypropylene, and the way that the plastics are manufactured,” he says.

If there’s any good news in this, it’s that “the level of microplastics released can be significantly reduced by following modified sterilization and formula preparation procedures,” according to the study. Indeed, a drastic reduction in the shedding of micro- and nanoplastics was observed when the plastic bottles were exposed only to water at lower temperatures (think: room temperature). As such, the team of scientists spearheading the study are calling on policymakers to reassess guidelines and procedures for the safer preparation of plastic bottles for feeding babies, according to a news release

Sterilization

In order to sterilize a bottle made of polypropylene, researchers suggest adhering to WHO guidelines, which involves boiling the bottles for up to five minutes and then allowing them to cool. Ideally you'll want to ensure the container used is a non-plastic material such as glass or stainless steel. Once the bottles have fully cooled, the recommendation is to rinse the bottle no less than three times using pre-sterilized, room-temperature water. 

Formula Preparation

Heat water used for formula preparation in a non-plastic container, like glass or stainless steel. Similarly, formula should be mixed in this type of container as well. Once the prepared formula has reached room temperature, it can be transferred to a plastic baby bottle (it’s important to note here that prepared formula should not sit at room temperature for longer than 2 hours, according to the CDC).

In addition to these revised safety guidelines, which will likely garner the attention of major health organizations, it’s prudent to continue to follow basic precautions when using any sort of plastics for food preparation. This may include reheating prepared formula in plastic containers and placing any sort of plastic containers in the microwave.

What This Means for You

While these study findings may sound alarming, it’s important to remember that while it's true microplastics are becoming more and more prevalent, scientists caution that more information is needed in order to know exactly how they affect us.

“This is a new and rapidly evolving area of research and the data on the potential impact on human health is not well developed,” says Wang. Until we know more, it’s best to keep liquids coming in contact with plastic baby bottles at room temperature (for no more than 2 hours) whenever possible. 

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Article Sources
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  1. U.S. Food & Drug Administration. Bisphenol A (BPA): Use in Food Contact Application. Updated June 27, 2018.

  2. American Academy of Pediatrics. Baby Bottles and Bisphenol A (BPA). Updated February 23, 2012.

  3. Godoy M. NPR. Study: Plastic Baby Bottles Shed Microplastics When Heated. Should You Be Worried?. October 19, 2020.

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  5. Centers for Disease Control and Prevention. How to Clean, Sanitize, and Store Infant Feeding Items. Updated July 8, 2020.

  6. World Health Organization. How to Prepare Formula for Bottle-Feeding at Home. 2007.

  7. U.S. Food & Drug Administration. 5 Tips for Using Your Microwave Oven Safely. Updated September 1, 2016.

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