Every baby bottle and sippy cup tested leaked bisphenols into drinks

Researchers tested 20 brands of baby bottles and 13 brands of sippy cups. Every single one released BPA and BPS into the liquid inside.

Environmental Health News reported the results on March 19, 2026. Leaching happened with plain water, and more with liquids formulated to mimic breastmilk and formula. No brand came back clean.

Which closes the usual escape route. Switching brands does nothing, because no brand is the variable here. The plastic is, and every one of these products is made of it.

How a bottle puts chemicals in milk

Bisphenols are not locked inside plastic, which is why a BPA-free label names only what is absent. They migrate out of the material into whatever liquid touches it.

The chemistry is plain. BPA and BPS build or harden the plastic without bonding into a fixed structure, so individual molecules separate from the surface and dissolve into the drink. Every feeding is a stretch of direct contact between container wall and milk.

Two conditions speed it up, and both are standard practice.

Heat. Warming a bottle raises how much the plastic releases. Parents warm milk and formula to body temperature routinely, which drives more bisphenol into the liquid at the exact moment of feeding.

Fat. Bisphenols dissolve more readily into fat than water. Breastmilk and formula both contain it, which is why the simulated milk pulled out more than plain water did. What makes milk nourishing is what extracts more chemical from the bottle.

Warm fatty milk sitting in plastic is the worst case, and it is also the normal case.

Why the label does not help

“BPA-free” describes the absence of one chemical. The tests make the gap concrete: these containers released BPS, the chemical that replaced BPA.

When studies tied BPA to hormonal and developmental effects and parents began avoiding it, manufacturers substituted close relatives, BPS most commonly. Same chemical family, nearly the same molecular structure. That resemblance is why BPS does the same job in a bottle and acts the same way in a body, mimicking estrogen and interfering with hormone signaling.

Researchers call it regrettable substitution: swapping a known hazard for a less-studied one that causes similar harm. A “BPA-free” bottle can be perfectly truthful about its label and still leach a bisphenol.

Estrogen mimicry, in a body still being built

Mimicry does it. BPA and BPS imitate estrogen, binding to the receptors the real hormone uses and sending signals nobody asked for.

Hormones work at very low concentrations and set the timing of development, so a small dose of something imitating them produces effects out of proportion to its size. The system being disrupted is the one directing how an infant’s brain, reproductive system and metabolic pathways get built.

Exposure is close to universal. The CDC detects bisphenol A in the vast majority of Americans it tests through its National Report on Human Exposure to Environmental Chemicals. A bottle contributes to that directly, delivered to the mouth at every feeding.

Three things make infants the worst case

Frequency. A newborn feeds eight or more times a day, each one a period of milk against plastic. Dose scales with use, and few objects an infant touches get used that often.

Timing. Hormonal signals guide construction of the brain, immune system and metabolic pathways through infancy. A disruptor arriving then interferes with signals a mature body would shrug off, because those systems are still being assembled.

Body size. A given amount of chemical delivers a larger dose per pound in a small body, and a bottle-fed baby takes in a lot of milk relative to its size. Cutting plastic out of food contact dropped urine chemical levels by 33% in a week in adults.

All three compound. A container leaching a small amount per feeding, used many times daily, in a small and fast-developing body, delivers far more than the per-feeding number suggests.

Glass, steel and silicone have nothing to give up

Material decides whether a bisphenol is even present.

Glass and stainless steel contain no BPA or BPS, so they have none to release. Silicone, used for nipples and some components, is not a bisphenol-based plastic and does not leach the way hard plastic does.

Label versus substance is the whole distinction. “BPA-free” is a claim printed on a plastic product the tests showed still leaches BPS. Glass, steel and silicone are different substances entirely, and changing what the container is made of beats trusting a label that carves out one molecule.

Sterilising makes plastic worse

Parents boil bottles or run them hot in the dishwasher to kill germs. Heat is also what drives the most leaching.

Transfer of BPA and BPS out of plastic rises with temperature. Boiling or a hot cycle increases release during the cleaning and afterward, because repeated heating degrades the plastic into shedding more over time. A routine meant to make a bottle safer makes a plastic one leach more.

Material resolves it. Glass and stainless steel take boiling and high-temperature cleaning with no bisphenol penalty, having none to release. The same swap works across every container in a kitchen.

Change the material

Feed from glass or stainless steel. Neither contains or releases BPA or BPS. Glass bottles with silicone sleeves add breakage protection without putting plastic against the milk.

Choose silicone nipples. Not a bisphenol-based plastic. Replace any hard plastic nipple or component.

Never heat milk in plastic. Warm it in glass or steel, or stand the bottle in a bowl of warm water. Never microwave milk in plastic.

Skip boiling and dishwasher sterilising for plastic parts. Warm soapy water and a good rinse instead. Glass and steel can be boiled safely.

Treat “BPA-free” plastic as a bisphenol risk. The tests found BPS coming out of exactly those products.

Replace worn plastic promptly. Scratched, cloudy or degraded plastic leaches more and harbors germs.

Extend it to sippy cups. The tests covered 13 brands of those too. Stainless steel or glass with silicone parts as a baby moves off the bottle.

Store milk in glass. Expressed breastmilk and prepared formula both, and use glass or steel for any warming step.

Twenty bottle brands, 13 sippy cup brands, every one of them leaking BPA or BPS into what a baby drinks. Heat and the fat in milk both make it worse, and the label naming one absent chemical does not stop the one that replaced it. Nobody filters a bisphenol out of a developing infant. Changing what the bottle is made of is the only part of this a parent controls.