In October 2022, a study published in the journal Polymers reported the detection of microplastics in human breast milk for the first time. Samples were collected from 34 healthy Italian women one week after giving birth. Microplastics were found in 75% of the samples. The finding confirmed what researchers had suspected: that plastic particles can cross multiple biological barriers and reach the breast milk produced to nourish newborns.
The 2022 study: what was found
The Polymers study analysed breast milk samples using Raman microspectroscopy, a technique capable of identifying plastic particles at sizes below 5 micrometres. Microplastics were detected in 26 of 34 samples at concentrations ranging from 2 to 12 particles per millilitre. The plastic types identified were polyethylene (the most common packaging plastic), polypropylene, polyvinyl chloride and polystyrene. No association was found between microplastic levels and diet, use of plastic containers or cosmetics during pregnancy, although the sample size was small. Larger subsequent studies have confirmed the finding across different populations.
What types of plastic were found and where they come from
The plastic types found in breast milk are consistent with common packaging and household materials: polyethylene from food packaging and plastic bags, polypropylene from bottle caps, food containers and microwave-safe packaging, PVC from piping and some food contact materials, and polystyrene from disposable cups and takeaway containers. The presence of these specific types suggests dietary and inhalation routes as the primary sources, consistent with what is known about general human microplastic exposure.
How microplastics cross from the gut to breast milk
Microplastics ingested through food and drink are partially absorbed through the gut epithelium, particularly smaller particles below 150 micrometres. Animal studies have demonstrated translocation of plastic particles from the gut to lymphatic tissue, blood, liver and other organs. In breastfeeding women, the bloodstream has direct access to mammary gland tissue and the milk produced within it. This same translocation pathway has been demonstrated for microplastics in studies of placental tissue: a 2020 study in Environment International found microplastics in human placentas from four of six samples tested.
What this means for breastfeeding decisions
Every major health organisation, including the World Health Organisation, UNICEF and the American Academy of Pediatrics, continues to recommend breastfeeding as the optimal infant nutrition. The benefits of breastfeeding for infant immune development, cognitive development, microbiome establishment and maternal health are well-documented and substantial. The presence of microplastics in breast milk does not change this recommendation. Formula preparation typically involves plastic scoops, plastic bottles and powder stored in plastic-lined tins. The microplastic exposure from prepared formula is not lower than from breast milk.
How to reduce infant exposure
Use glass or stainless steel for formula preparation
If preparing formula, use a stainless steel or glass kettle, glass measuring cups and stainless steel bottles. This reduces microplastic introduction during preparation.
Never heat milk in plastic
Never heat breast milk or formula in plastic bottles, even BPA-free ones. Transfer to glass or stainless steel before warming. Heat accelerates plastic particle and chemical release.
Reduce maternal dietary plastic exposure
The primary routes for maternal microplastic accumulation are drinking water (switch to filtered tap) and eating food stored or heated in plastic. Reducing these during pregnancy and breastfeeding reduces the microplastic load available for transfer.