Baby Bottles May Shed Millions of Microplastic Particles Into Infant Formula, Review Finds

Every day, millions of parents around the world prepare infant formula in plastic bottles, trusting that the products they feed their babies are as safe as modern science can make them. A new scoping review published in Environmental Science and Pollution Research suggests that this trust deserves closer scrutiny. Researchers at Universidad de La Sabana in Colombia systematically combed through a decade of scientific literature and found that infant formula and its packaging can expose babies to both microplastic particles and endocrine-disrupting chemicals, sometimes at strikingly high daily levels, during one of the most sensitive windows of human development.

The review, led by Maria Camila Amaya and colleagues, followed the established Joanna Briggs Institute methodology and the PRISMA-ScR reporting guidelines, the gold standards for transparent evidence synthesis. The team searched multiple scientific databases for studies published between 2015 and 2025, applying predefined inclusion and exclusion criteria to every candidate paper. From an initial pool of 223 articles, only 27 survived the rigorous selection process, a winnowing that reflects both the novelty of the field and the uneven quality of the available evidence. The extracted data were synthesized in a standardized matrix, allowing the researchers to map where the evidence is strong, where it is thin, and where it is entirely absent.

Perhaps the most eye-catching finding concerns the sheer scale of particle release during ordinary bottle feeding. Previous work, prominently a study published in Nature Food, documented that polypropylene feeding bottles can shed millions of microplastic particles per liter during formula preparation, particularly when hot water is used to sterilize and mix the contents. Polypropylene is the workhorse plastic of baby bottles, prized for its durability and heat resistance, but those same properties do not prevent mechanical and thermal stress from liberating microscopic fragments directly into the liquid an infant drinks. For a baby consuming several bottles a day, the review notes, this can translate into exposure to high daily particle levels from a single, routine source.

The chemical side of the contamination story is equally concerning. The studies included in the review identified bisphenols, phthalates, and other endocrine-disrupting chemicals in infant formula, baby food, and their packaging materials. These compounds are not exotic contaminants; they are integral components or additives of the plastics that surround our food. Bisphenol A, even where restricted, has been partly replaced by structural cousins that may migrate from polyester-phenol coatings and multilayer plastic pouches. Phthalate esters have been quantified in powdered formula from multiple countries, and organophosphate flame retardants have been detected in baby foods, with infants showing notably high exposure linked to plastic baby products.

What makes early-life exposure to these chemicals so consequential is the biology of the developing endocrine system. Endocrine-disrupting chemicals can interfere with thyroid hormones, oestrogenic signaling, and metabolic regulation, and decades of toxicological research have established that such interference can produce effects at very low doses, sometimes following non-monotonic dose-response curves in which lower exposures are not necessarily safer. The Endocrine Society’s scientific statements have repeatedly warned that critical developmental windows, including gestation and infancy, are periods when hormonal disruption can reprogram tissues with consequences that may not become apparent for years. The review’s authors emphasize that infants, with their higher relative food intake per body weight and immature detoxification systems, sit squarely within these vulnerable windows.

The evidence on health effects, while still limited, points in a coherent direction. Studies reviewed by the team reported alterations in the intestinal microbiota of infants exposed to microplastics via baby bottles, including changes in short-chain fatty acid profiles, which are key metabolic messengers produced by gut bacteria. Other work documented shifts in immune-related biomarkers and responses; one longitudinal cohort linked plasticiser exposure to measurable changes in infant immune parameters, and separate research associated phthalate exposure with altered gut microbiota composition and modified IgM vaccine responses in human newborns. Experimental studies in rodents have shown developmental and reproductive toxicity from polystyrene microplastics, and lactational exposure at infant-equivalent doses induced transgenerational reproductive toxicity in female mice, findings that, while not directly transferable to humans, underscore the biological plausibility of harm.

The contamination pathway begins even before birth. The review highlights evidence of prenatal exposure, building on landmark studies that detected microplastics in human placental tissue and in maternal and foetal samples, as well as microplastics identified in human breast milk. This means that the bottle and the formula are not the first exposure an infant encounters; they are an additional layer on top of a body burden that may already exist at delivery. Human biomonitoring studies have found microplastics in stool samples, lung tissue, and blood, confirming that these particles circulate through the body rather than passing through inertly. In vitro work adds a mechanistic dimension: polystyrene microplastics have been shown to compromise intestinal barrier function and interfere with protein digestion, and polypropylene particles can affect the digestion of cow’s milk proteins, the very proteins that form the nutritional backbone of standard formula.

Complicating the scientific picture is the difficulty of measuring contamination accurately. One study included in the review raised the possibility that plastic additives can generate false positive errors in microplastic detection within infant feeding bottles, a reminder that analytical methods in this young field are still being refined. Detection limits, particle identification techniques, and the distinction between micro- and nanoplastics all vary across studies, which helps explain why the authors repeatedly characterize the evidence base as limited. Most of the health findings derive from experimental, animal, or observational studies rather than from the longitudinal human cohorts that would be needed to establish definitive cause-and-effect relationships in infants.

That evidentiary gap is precisely what the review’s authors identify as both a problem and a call to action. The absence of strict regulations specifically governing microplastics and endocrine disruptors in infant formula and feeding equipment, combined with the scarcity of long-term studies tracking exposed children over time, reinforces what they describe as an urgent need to advance public policies controlling these agents and to promote health education that helps families reduce exposure. Regulatory frameworks for food contact materials were largely built before the era of microplastic science, and they typically assess chemicals one at a time rather than the complex mixtures that migrate from real-world packaging.

For parents, the review does not prescribe panic, but it does suggest that precaution is reasonable while the science matures. Practical steps highlighted in the broader literature include minimizing the heating of plastic feeding bottles, considering alternative materials where feasible, and following preparation guidelines that reduce particle shedding. The larger burden, the authors argue, lies with manufacturers and regulators: if millions of particles per liter can be released during ordinary formula preparation, and if endocrine-active chemicals are consistently detected in the products and packaging designed for the most vulnerable consumers, then the current regulatory silence on these contaminants in infant nutrition is increasingly difficult to justify. As microplastic research moves from environmental oceans into pediatric wards, this scoping review makes clear that the question is no longer whether infants are exposed, but how much, with what consequences, and what society is prepared to do about it.

Subject of Research: Microplastic and endocrine-disrupting chemical contamination of infant formula and its potential early-life health effects

Article Title: Microplastic and endocrine disruptor contamination in infant formula and early health effects: scoping review

Article References: Amaya, M. C., Rodriguez, S. D. B., Burgos, J. S., & Rincon, E. H. H. (2026). Microplastic and endocrine disruptor contamination in infant formula and early health effects: scoping review. Environmental Science and Pollution Research, 33(30), 15285-15297. https://doi.org/10.1007/s11356-026-38153-5

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38153-5

Keywords: microplastics, infant formula, endocrine disruptors, baby bottles, plastic pollution, environmental health, pediatrics, gut microbiota, bisphenols, phthalates, child development, public health