Is it safe to drink from a plastic water bottle left in a hot car?
No. Car heat drives microplastics and plasticizer release from PET bottles into the water.
What's actually in it
PET bottles (recycling 1) are stable at room temperature. Inside a car on a sunny day, surface temperatures can hit 60-80°C. At that heat, PET releases antimony (used as a catalyst), acetaldehyde (a degradation product), and more microplastic particles.
Antimony is a metalloid toxic to kidneys at high doses. Acetaldehyde is a known carcinogen.
What the research says
A 2025 study in Environ Monit Assess detected microplastic fragments in nearly every bottle of drinking water tested. A 2025 study confirmed particle release scales with temperature.
Keep water bottles out of the car when possible. For commutes and travel, use a stainless steel or glass insulated bottle. If a bottle has been sitting in a hot car, pour it out.
The research at a glance
| Study | Journal | Year |
|---|---|---|
| Microplastics in drinking water bottles and milk packaging. | Environ Monit Assess | 2025 |
| Release of Nanoplastics from Polypropylene Food Containers. | J Agric Food Chem | 2025 |
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