A team of research scientists from Trinity College Dublin in Ireland published a study on October 19, 2020, in the peer-reviewed journal Nature Food estimating that infants could ingest up to 4.5 million plastic particles per day when fed from polypropylene baby bottles. Applying cleaning, sterilizing, and mixing procedures recommended by the World Health Organization (WHO) for preparing baby formula, the team examined the release of plastic microparticles from a set of ten new polypropylene baby bottles into water. Raman spectroscopy and atomic force microscopy were used to measure the quantity and sizes of microplastics. A recovery test and a blind external laboratory test were carried out to confirm the reliability of the analytical methods used.

During a 21-day test, the authors observed microplastics release rates that fluctuated in a range from just a few thousand to as high as 16.2 million particles per liter. Based on bottle-feeding rates from 48 different regions, they determined that infants up to 12 months old that are fed using polypropylene bottles may be exposed to a range from 14,600 to 4.55 million particles per infant per day.

Co-author of the study John Boland told The Guardian that “we were absolutely gobsmacked” by the high number of microplastics produced by the baby bottles. “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,” he said. The scientists suggest that an additional washing step after sterilization and before filling the bottle with formula can reduce the exposure to microplastics. Polypropylene is reported to make up 82% of the global baby bottle market, with glass bottles being the primary alternative. Boland goes on to say “the last thing we want is to unduly alarm parents, particularly 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.”


Li, D. et al. (October 19, 2020). “Microplastic release from the degradation of polypropylene feeding bottles during infant formula preparation.” Nature Food

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Damian Carrington (October 19, 2020). “Bottle-fed babies swallow millions of microplastics a day, study finds.” The Guardian

CHEM Trust (November 2020). “New study shows that plastic baby bottles can release millions of microplastics per day.”