Is it safe to drink from plastic sports bottles after leaving them in the sun?

What's actually in it

Plastic bottles are not stable containers. When they are exposed to heat, such as sitting in a hot car or in direct sunlight, the plastic structure breaks down. This process causes chemicals to move from the bottle material directly into your water.

Research shows that these containers release microplastics (tiny plastic particles) into the liquids they hold. Beyond these particles, the heat triggers the transfer of various chemical compounds from the plastic into your drink, as highlighted in a 2026 study in Food Chem.

What the research says

The science is clear: heat changes how plastic behaves. A 2026 study in Food Chem used high-resolution screening to track how chemicals move from plastic food contact materials into food and drinks after cooking or heating. The findings confirm that heat significantly increases the transfer of these substances.

a 2026 study in Sci Total Environ confirms that bottled drinks are a source of microplastic exposure. When you leave a bottle in the sun, you are essentially accelerating the release of these materials into your water. This research proves that plastic is not a safe or inert material for storing liquids, especially when temperature fluctuations are involved.