Plastic baby feeding bottles shed microplastic particles, say researchers

Plastics have been a part of our lives since the creation of the first plastic bottle more than a hundred years ago. But, do you know that the tiny bits of plastic that make up the bibs, bottles, and packaging also shed tiny microscopic particles?

Previous studies have shown that microplastics are present almost everywhere in the environment. Most of the plastic products we use are regularly shedding these tiny microscopic particles, say researchers. For example, plastic bottles or microwave containers made of polypropylene are known to shed these particles. Baby feeding bottles are also made of polypropylene, and thus shed microplastic particles, says a new study.

This new study from researchers at Environmental Engineering, Trinity College Dublin, and the Medical University of Vienna shows that an average of 1 million microplastic particles per day are consumed by infants drinking from these feeding bottles. The study results are published in the latest issue of the journal Nature Food.

Previous research has shown that adults and children in the United States are consuming between 74,000 and 211,000 microplastic particles in a year from the food and water they consume as well as from the air breathed in. However, this new study shows that the numbers could be much higher.

Microplastics in feeding bottles

This study came about by chance when one of the researchers poured hot water into a plastic container to prepare instant noodles. The container looked rigid to start with, but it changed to become more malleable and soft after he poured hot water into it. The researcher was curious and wondered whether microplastics were being released in the process. This raised suspicion that the plastic interiors could be releasing plastic microparticles into the food. A lab investigation showed that the container released over a million microplastics per liter of hot water.

This started a chain of tests where the team looked at other polypropylene containers, such as plastic bottles. At room temperatures, the release of microparticles was less, they noted. When heated, the number of microplastic particles released rose, they wrote. The heat was the key factor, they concluded.

Next, they tested baby feeding bottles made of polypropylene. This is one of the plastic containers that was repeatedly subjected to heat, they wrote. Next, they searched for baby feeding bottles made in 48 different regions around the world, covering around 78 percent of the world population. The authors of the study found that 83 percent of the feeding bottles used for babies and infants were made of polypropylene.


Next, ten different baby feeding bottles underwent lab testing. The World Health Organization (WHO) has laid down specific rules in 2007 to prepare bottle feeding formula at home. While testing the bottles at the labs, the team followed these guidelines.

Some of the steps for preparation of the formula included:

  • Cleaning
  • Sterilizing
  • Mixing the formula and shaking

The procedure, controls, and testing were rigorously performed to ensure no errors were encountered. The tests were also repeated using an independent lab for verification. The results from the lab were similar to what was found in this study.


Process of sterilization

During sterilization, bottle parts are often disassembled and placed in a pan full of boiling water. The temperatures are often around 95°C. This raises the release of microplastics by 35 percent, the researchers found.

Process of preparation of formula

They followed these steps for the ten bottles and found that up to 16 million particles per liter of 70°C water were released. These microparticles were found to be less than 20 micrometers in diameter and appeared flake-like under the microscope. They also had a coarse surface, and their thickness was around one-tenth of their width on average.

As the water temperatures rose from the recommended 70°C up to 95°C, the release of microplastics also rose from six million particles per liter to 55 million. The team explained that 95°C is the temperature of recently boiled water, which is commonly used for the preparation of baby formula milk.

Reducing exposure

The study shows that babies and infants drinking out of polypropylene bottles could be consuming more microplastic particles than known before. Infants around the world consume an average of 1.6 million polypropylene microplastic particles each day.

The researchers recommend certain ways to reduce exposure to microplastics. Some of the ways include:

  • Sterilized feeding bottles should be rinsed with cool sterile water before the formula is prepared in them.
  • Formula should be prepared in a non-plastic container.
  • Once the formula has reached room temperature, it is fit to be transferred into the sterilized and then a cooled bottle.
  • The prepared formula in plastic bottles should not be re-warmed using a microwave oven.

Philipp Schwabl, a physician and researcher at the Medical University of Vienna, and first author of the study, said, "At the moment, there is no need to be afraid... But it is an open question and definitely an unmet [research] need."

Co-author, John Boland, a professor of chemistry and materials science researcher at Trinity College Dublin in Ireland, added, "The last thing we want to do is unduly alarm parents when we don't have sufficient information on the potential [health] consequences. However, we are calling on policymakers to reassess the current guidelines for formula preparation when using plastic infant feeding bottles." He added that since plastics are useful and "here to stay," "we will have to make them safer and more resilient."

Journal reference:
Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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