Are compostable plastics like PLA always safer than regular plastic?
Not always. PLA can still become microplastic. A 2026 mouse and cell study found PLA microplastics caused heart changes in adolescent mice through senescence and ferroptosis pathways.
What's actually in it
PLA, or polylactic acid, is a plant-based plastic. It is used in some compostable cups, cutlery, and food packaging.
Compostable does not mean it disappears in your kitchen trash or backyard compost. PLA usually needs industrial composting conditions. If it breaks into tiny pieces first, it can still become microplastic.
What the research says
A 2026 study in Toxicology exposed adolescent mice to PLA microplastics for 28 days. The mice showed heart-development changes, including disorganized heart cells, thinner heart muscle, and fibrosis.
The researchers also found signs of cardiomyocyte senescence and ferroptosis in mouse heart tissue and heart cells. This was an animal and cell study, not a human food-packaging trial. Still, it shows that PLA microplastics should not be treated as automatically harmless.
What to do
Use compostable plastic only when you need disposable items. For everyday meals and drinks, choose durable materials like stainless steel kitchen swaps, glass, or ceramic.
The research at a glance
| Study | Journal | Year |
|---|---|---|
| Adolescent exposure to polylactic acid microplastics causes cardiac fibrosis by promoting cardiomyocyte senescence. | Toxicology | 2026 |