Most parents check for BPA-free before they register. What the label doesn't cover is what happens when that plastic gets hot, and hot water is how formula gets made.
BPA-free doesn't mean microplastic-free.
Most plastic baby bottles are made of polypropylene. It's BPA-free, and that part is good news.
In 2020, researchers at Trinity College Dublin followed the steps parents use to make formula in polypropylene bottles, then counted the particles the bottles released into the water. They published the results in Nature Food.1
The study tested polypropylene bottles, not Jili. Scientists are still studying what that means for babies.
Should you stop using plastic baby bottles? Hotter water, more particles.
The amount depended on the water temperature:
- 77°F: about 0.6 million particles per liter.1
- 158°F: up to 16.2 million particles per liter.1
- 203°F: up to 55 million particles per liter.1
158°F matters because it's the temperature the CDC gives for mixing powdered formula for babies under 2 months, born early, or with a weakened immune system.2 For those parents, hot water isn't optional.
Stainless steel vs plastic: what parents are switching to.
Glass keeps hot water out of plastic. It's heavier, and it can break, which is why many parents keep glass at home.
Stainless steel also keeps hot water out of plastic, it won't shatter in a diaper bag, and an insulated steel bottle keeps water warm.
Either way, the nipple is usually silicone, and the plastic question shifts from the bottle to a few small parts.
Where Jili fits.
Jili holds the hot water in 18/8 stainless steel. The formula waits dry in the base until your baby's hungry, so every bottle is mixed fresh. The nipples are food-grade silicone, and the lid and funnel are TPE.3
The study tested polypropylene bottles, not Jili. Scientists are still studying what that means for babies.
Jili keeps the formula dry in the base until your baby's hungry, so the bottle you shake at the park is as fresh as one made at home.
Shop Jili · $45- Li, D. et al. Microplastic release from the degradation of polypropylene feeding bottles during infant formula preparation (opens in a new tab). Nature Food, 2020. Accessed October 2026.
- Centers for Disease Control and Prevention. Infant Formula Preparation and Storage (opens in a new tab). Accessed October 2026.
- Jili. All-In-One Baby Bottle: product details. Accessed October 2026.