Do polypropylene food containers release nanoplastics into hot water?

What's actually in it

Polypropylene (PP) is the plastic used in most "microwave-safe" food containers, yogurt cups, and takeout tubs. It's labeled with recycling code #5. While it holds up well to heat without melting, that doesn't mean it stays intact at the nanoscale. Hot liquids break loose tiny particles from the plastic surface that are invisible to the naked eye.

Nanoplastics are particles smaller than 1 micrometer. They're so small they can cross cell membranes and enter your bloodstream. They're also nearly impossible to filter out once they're in your food or drink.

What the research says

A 2025 study in J Agric Food Chem measured nanoplastic release from polypropylene food containers filled with both hot and cold water. Hot water released dramatically more nanoplastics than cold water. The numbers were in the billions of particles per liter.

The hotter the water, the more particles came loose. Boiling water was the worst, but even warm tap water released measurable amounts. Repeated use and washing also increased particle release over time as the container surface degraded.

These nanoplastics are small enough to be absorbed through the gut wall and into your organs. If you're pouring hot soup, coffee, or boiling water into polypropylene containers, you're getting a large dose of nanoplastics with every serving. Glass or stainless steel containers don't have this problem.