Do chemicals from plastic bottles leach into stored breast milk?

What's actually in it

When you pump and store breast milk in a plastic bottle or storage bag, the milk sits in direct contact with the plastic for hours or even days. Breast milk contains fats that are especially good at pulling chemicals out of plastic. That means phthalates, microplastics, and other additives can migrate from the container walls into the milk your baby will drink.

This is on top of whatever chemicals are already in the milk from the mother's own exposures. Breast milk has been shown to carry traces of environmental chemicals the mother absorbed through food, water, and air.

What the research says

A 2026 study measured phthalate and DINCH metabolites in both urine and breast milk from nursing mothers. The results confirmed that these plasticizer chemicals are present in breast milk at measurable levels, meaning infants are directly exposed through nursing.

A 2026 study from Saudi Arabia found perfluoroalkyl compounds (PFAS) in breast milk samples. These forever chemicals came from the mothers' exposure to nonstick cookware, food packaging, and contaminated water.

Research on microplastics in packaged milk found that plastic containers release detectable particles into liquid milk during storage. The longer the storage time and the higher the fat content, the more particles leach out.

A 2026 study went further, showing that polystyrene microplastics can actually disrupt the beneficial bacteria that transfer from mother to baby through breast milk. These bacteria are critical for building the infant's immune system and healthy gut.

The bottom line

Glass bottles are the safest choice for storing pumped breast milk. They do not leach plasticizers, microplastics, or chemical additives. If glass is not practical, food-grade silicone bags are a better alternative than standard plastic storage bags. Avoid heating breast milk in plastic containers, as heat speeds up chemical migration.