Do polypropylene food containers shed nanoplastic when you pour boiling water in them?

What's actually in it

Polypropylene, marked with the #5 recycling code, has a reputation as the safer plastic. It doesn't use bisphenols, and it handles dishwasher heat better than most. The catch is that hot liquid still pulls plastic out of the surface, in the form of nanoplastic particles too small to see.

You'll find polypropylene in deli soup tubs, instant noodle bowls, baby bottles, and most reusable food storage with a hinged lid.

What the research says

A 2025 study in J Agric Food Chem poured hot and cold water into polypropylene food containers and counted what came out. Hot water released billions of nanoplastic particles per container in a single use. Cold water released far fewer. The hotter the water, the bigger the count.

The team noted that even short contact with boiling water, like steeping noodles or formula, was enough to push the count high.

Skip pouring boiling water into polypropylene. Use a glass or ceramic bowl for hot soup, instant noodles, and tea. Cool food before storing it in plastic, and never microwave food in a plastic tub even if the lid says "microwave-safe."