Is it safe to buy kids' lunchboxes made from plastic with silicone lids?
Not ideal. The plastic body is in contact with food all morning and often goes in the microwave.
What's actually in it
Marketing often foregrounds the silicone lid or divider while the main compartment is polypropylene or Tritan plastic. Food sits in that tray from breakfast prep until lunch at school: four to six hours of contact time, including the ride in a warm backpack. When parents send leftovers, the tray often goes in the microwave at home first to pack warm food, then back in the microwave at school for a few seconds of reheat.
Popular "PlanetBox" style stainless sets are different: the main body is metal, with silicone seals. Plastic-bodied lunchboxes are much cheaper and far more common.
What the research says
A 2025 study in J Agric Food Chem measured nanoplastic release from polypropylene food containers into hot and cold water. Both hot and cold conditions released plastic. For a lunchbox, the full day of contact at body-warm temperatures falls squarely in this range, even without a microwave step.
A stainless steel bento with silicone seals is the cleanest daily lunchbox. It's more expensive up front (around $30 to $60) and lasts many years. For families staying with plastic, a simple fix is to pack food in small glass or stainless inner containers that fit inside the plastic outer shell, so the food contacts glass or stainless instead of plastic. And skip warm food that sits in the box: pack cold, eat cold.
The research at a glance
| Study | Journal | Year |
|---|---|---|
| Release of Nanoplastics from Polypropylene Food Containers into Hot and Cold Water. | J Agric Food Chem | 2025 |
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