What the baby bottle study found
Emerging In 2020, researchers at Trinity College Dublin tested 10 common baby bottles made of or containing polypropylene, following World Health Organization guidance for cleaning, sterilizing and preparing formula. The bottles released between 1.3 and 16.2 million microplastic particles per liter, plus far larger numbers of nanoplastics.
Temperature drove the results. At 25°C (room temperature) bottles released about 0.6 million particles per liter; at the 70°C used for mixing formula, much more. Vigorous shaking added to it. Using bottle-feeding rates in 48 regions, the team estimated that bottle-fed babies in their first year take in about 1.6 million particles a day on average. Polypropylene makes up roughly 80% of the global baby bottle market. The same team found polypropylene kettles and lunch boxes shed at similar levels.
No one yet knows what this means for babies' health. But infants are small, still developing, and take in more per kilogram than adults, so reducing exposure is a sensible precaution.
Safer formula preparation, step by step
These steps come from the study team's own recommendations, which they tested and found greatly reduced particle release. They work alongside, not instead of, your local health authority's hygiene advice.
- Sterilize the bottle the way your health authority recommends.
- Boil water in a non-plastic kettle or pan, such as stainless steel or glass.
- Rinse the sterilized bottle three times with that boiled water once it has cooled to room temperature. This washes away particles released during sterilizing.
- Mix the formula in a glass or stainless steel container using water of at least 70°C, as food-safety guidelines require.
- Let it cool to feeding temperature, then pour it into the bottle.
- Swirl gently rather than shaking hard.
- Never reheat formula or milk in a plastic bottle, especially in a microwave. Warm it in a glass container in a bowl of warm water instead.
Easiest option: glass bottles avoid most of these steps. Choose ones with a silicone sleeve if you worry about breakage.
Baby food and toddler meals
- Don't microwave food in plastic pouches or tubs. In a 2023 study, heated baby-food containers released billions of nanoplastics per square centimeter. Infants drinking microwaved water and toddlers eating microwaved dairy had the highest estimated intake.
- Squeeze pouches are convenient for travel; at home, spoon food from a bowl.
- Use stainless steel, glass or ceramic plates, cups and lunch boxes for warm food.
- Be cautious with melamine and "bamboo" plates that are bound with melamine resin, which can break down with heat.
Toys, teethers and the nursery
- Choose teethers made of natural rubber, food-grade silicone or wood.
- Babies crawl through floor dust, which collects synthetic fibers. Vacuum with a HEPA vacuum and wipe floors with a damp cloth.
- Natural-fiber rugs, bedding and sleepwear reduce fibers in the air around a sleeping baby.
Frequently asked questions
Are glass baby bottles better than plastic?
For microplastics, yes. Glass does not shed plastic particles. Many parents use glass bottles with a silicone sleeve to reduce breakage. If you use plastic bottles, the preparation steps on this page reduce shedding a great deal.
Are silicone baby bottles and nipples safe?
Silicone is not a conventional plastic and is more heat stable, but research on particle release from silicone is limited. It is generally considered a reasonable alternative to polypropylene, especially for nipples, which have few other options.
Should I still sterilize plastic bottles?
Yes. Follow your health authority's sterilization advice to protect your baby from infection. Then rinse the sterilized bottle at least three times with room-temperature water that was boiled in a non-plastic kettle, which removed most released particles in tests.
Is breastfeeding free from microplastics?
Some studies have reported microplastics in breast milk, though measurement quality varies. Breast milk's well-established health benefits far outweigh this uncertain concern, and health authorities continue to recommend breastfeeding where possible.
Keep reading
Sources
- Li et al. (2020), Microplastic release from the degradation of polypropylene feeding bottles during infant formula preparation, Nature Food
- Trinity College Dublin (2020): recommended sterilisation and formula preparation procedures
- Hussain et al. (2023): microwaving baby food containers (University of Nebraska–Lincoln)
- Food Packaging Forum (2020): study summary on baby bottle microplastics