Plastic Baby Bottles Shed High Levels of Microplastics When Heated During Formula Prep

by DailyHealthPost Editorial

The presence of microplastics in water has been a well-known problem for a long time. However, a recent study published in the Nature Foods journal points to the fact that microplastics may be released in dangerously large quantities from baby bottles when they’re used for the standard preparation of baby formula.

What exactly are microplastics?

For a quick crash-course of the problem, microplastics are exactly what they sound like – microscopic pieces of plastic that are torn from large plastic objects such as water bottles over time. This happens either when the plastic is subjected to extreme heat, be it from a kitchen appliance or from sun exposure, or when it’s just deteriorating over time.

These microscopic pieces of plastic are so small that they are often invisible to the human eye in normal conditions. Due to pollution, they are generally found in many water sources right now and are often discovered in marine fish.


Their exact threat level upon ingestion is somewhat unclear. Some studies and reports conclude that there’s no concrete evidence about the danger posed by microplastics as of now. Many other studies, however, claim that microplastics often cause a lot of damage when they pass through our bodies – from direct physical damage to our organs to leaking hazardous materials in our systems such as the hormone-disrupting bisphenol A (BPA) or pesticides.

Aren’t baby bottles of high enough quality to be safe?

Most people by now are aware that thin and flimsy water bottles are too poorly made and therefore easily leak microplastics. Aren’t baby bottles and other more well-made plastic bottles BPA-free and durable though?

According to the recent study published in Nature Foods, bottle-fed infants worldwide are likely consuming over 1.5 million particles of microplastics per day. While this sounds horrifying, experts urge that there still isn’t enough data to suggest a course change.

Philipp Schwabl, one of the physicians and researchers from the Medical University of Vienna who authored a 2018 study and was the first to document microplastics in human excrements says that people shouldn’t panic.

“At the moment, there is no need to be afraid,” said Philipp Schwabl. “But it is an open question and definitely an unmet [research] need.”

The sentiment is echoed by John Boland, a chemistry professor and materials science researcher from the Trinity College Dublin and one of the researchers on the new Nature Foods study. According to Boland, “The last thing we want to do is unduly alarm parents.”


He also pointed out that the release of microplastics happens mostly when the bottles are heated to high temperatures.

“What’s happening is that there’s an interaction between the [plastic] polymer and the water,” Boland said. “It’s almost like a flaking of the surface of the actual plastic itself.”

Although, Boland adds that mere shaking of the bottle also leads to a small amount of microplastic flaking. During the study, the researchers would fill the bottled with room temperature water and shake them for ~60 seconds, as per the standard instructions for the preparation of baby formula. Under these “normal conditions”, the researchers observed the release of “hundreds of thousands of microplastics” per bottle” Boland said. When the temperature was increased, those hundreds of thousands jumped up to millions.

The researchers also observed a large number of nanoplastics together with the microplastics. According to them, the number of nanoplastics was in the trillions and “we stopped counting them,” at a certain point.

If you’re wondering what nanoplastics are, these are essentially microplastics that range in size between 10 nanometers and 1 micron.

The plastic baby bottles kept releasing micro and nanoplastics throughout all 21 days of testing per bottle. 


Why are the researchers so calm about this?

The reason experts like Boland and Schwabl are urging for calmness is that they are still too early into the research for anything to be conclusive. Boland points out that the reason he and his team chose to focus on baby bottles is that there’s a very small number of products on the market.

Worldwide, polypropylene baby bottles make up for 82% of the baby bottle market and they are all made by a very small number of manufacturers. This is great for the researchers as it allows for a “comprehensive view of the market, and that also allowed us to actually look at the global potential of this issue,” Boland said.

Overall, the 10 different types of plastic baby bottles examined by the researchers were representative for as much as 70% of all baby bottles on the international market.

As for the average number of 1.5 million pieces of microplastics consumed per day by every infant, the researchers say that these numbers vary per country and per region. For example, in the U.S. and western Europe where breastfeeding rates are below the average, the number is estimated to be well over 2 million units of microplastics.

In China, on the other hand, glass baby bottles are more popular and there the averages are significantly lower. In other Asian countries and Africa, the problem is even smaller as breastfeeding is much more common there.

Still, the researchers emphasize the fact that the effects of the injestion of microplastics aren’t conclusive yet. There are many reports about the dangers of them but there are some that don’t find any solid evidence yet. “The threshold at which they cause problems has not been determined for humans,” Schwabl said.


Boland does have several recommendations for parents who want to minimize the consumption of microplastics, however:

  • Never use a microwave for preparing baby formula as microwaves don’t just heat the liquid, they also create “pockets of really superheated water adjacent to the plastic, and that gives rise to copious quantities of microplastics.”
  • Sterilize the plastic bottles in hot water after every 2-3 feedings and then let them cool down completely. Then, rinse the sterilized bottles with water that’s been boiled and has also been allowed to cool down to room temperature. 
  • When preparing baby formula, Boland also recommends that parents do so with 158Fo as per the standard instructions but in a glass container and not in the plastic baby bottle. Only transfer the formula into the plastic bottle once it has cooled down to room temperature.

Or, you can just use glass bottles instead. 

How do these levels of microplastic-shedding compare to other products?

Plastic baby bottles aren’t the only frequently used items that shed plastic in our day-to-day lives. A 2019 study published in ACS Publications states that plastic tea bags can also release billions of plastic microparticles when placed in boiling water. Schwabl also talks about them in a commentary published in Nature Food.

Similar findings have been made by colleagues of Boland from the Trinity College Dublin about plastic food storage containers, plastic instant noodle cups, plastic tea kettles, and other such items. Schwabl notes that all these items require further research as do plastic microparticles in general.

Another interesting point is raised by David Love, an associate scientist at the Jon Hopkins Center for a Livable Future. He points out that nanoplastics may be a much bigger problem than microplastics.

“We’re probably excreting most of the microplastics that we ingest,” David Love says and adds that it’s the much smaller nanoplastics can “actually make their way into the bloodstream and from there transport throughout the body.” 


Like his colleagues, Love agrees that much more research is needed for both types of plastic particles. The researchers also urge people to limit the amount of plastic they use in their daily life both to be safe and as a general environmental precaution. Schwabl points out that he’s limited his use of plastic containers “not so much that I am afraid of the ingestion, but I think thereby I may be contributing to [reducing] the amount of plastic waste.”

Love also agrees, saying that “What this study and other studies are telling us is that we should be asking this of our regulatory agencies — and they should be exploring — what these risks are and developing guidance for industry in terms of what is the appropriate level of microplastic shedding from high-risk products like baby bottles.”

Are glass baby bottles the way to go?

As far as the risk of microplastic and nanoplastic shedding, glass bottles seem to be the clearly better option. They are also easier to clean and sanitize, eating from them is said to taste better, they are more durable overall, and they are usually compatible with breast pumps.

The downside is that glass bottles tend to be more expensive and less readily available in the Western world. They are also heavier which may be a problem for the youngest infants and there is a small risk of breakage. 

Overall, however, we lean toward glass baby bottles. The price issue is negligible given that this isn’t a frequent purchase, the availability can be dealt with thanks to online shopping and international shipping, and as for the safety – there are nice silicone sleeves for baby bottles on the market which can protect your child from harm should the bottle accidentally crack. And if you don’t want to purchase a silicone sleeve, cloth or leather sleeves can also be easily made or purchased.