Think twice before sipping from that plastic bottle in your car: new study links it to potential health risks

Leaving a bottle of water in your car on a hot day might seem harmless, but research shows it can change what’s actually in that water. Heat speeds up the release of chemicals from plastic, and some of those substances are linked to serious health concerns.

Scientists have found that BPA, microplastics, and other compounds can leach into water when bottles are exposed to high temperatures, like those inside a parked car. Here, we’ll look at what the latest study uncovered, how quickly this happens, and what safer options you can use to stay hydrated without the added risks.

What the study found about heat and bottled water

A study published in the International Journal of Environmental Research and Public Health examined how heat affects the migration of chemicals from plastic bottles into water.

The researchers looked specifically at bisphenol A (BPA) and antimony, both of which are used in manufacturing many disposable bottles. BPA is known for its potential to disrupt hormones, while antimony has been associated with nausea, vomiting, and diarrhea at high levels.

The findings were clear: the higher the temperature and the longer the bottle was exposed, the more chemicals ended up in the water. Even moderate heat made a difference. On an 80°F day, the temperature inside a parked car can climb above 110°F in less than 30 minutes, conditions that significantly increased BPA migration in the study.

Microplastics were also detected. These tiny fragments come from the breakdown of plastic over time and can enter the body through ingestion. While their full health effects are still being studied, research suggests they can accumulate in organs, trigger inflammation, and interfere with normal cellular processes.

The concern isn’t just a single hot day. Because drinking water is a daily habit, repeated small exposures can add up over weeks, months, or years. That’s why the researchers stress that these risks aren’t limited to extreme conditions—they can happen whenever bottled water is stored in warm places for long periods.

How to protect yourself and safer ways to hydrate

While the findings might sound alarming, avoiding the problem is straightforward. The simplest step is not leaving bottled water in hot environments, whether in cars, sunny windowsills, or gym bags in the heat. Keeping bottles in cool, shaded places reduces chemical migration.

Switching to reusable bottles made from stainless steel or glass is another reliable option. These materials don’t leach BPA or similar chemicals, and insulated versions keep water cold for hours, even in summer heat. For people who still prefer plastic bottles for convenience, look for products labeled “BPA-free”, though experts caution that BPA substitutes like BPS or BPF may pose similar risks.

At home, store bottled water away from direct sunlight and away from appliances that produce heat, like ovens or radiators. If you buy bottled water in bulk, rotate stock so older bottles are used first, and avoid storing them in garages or sheds that can get hot.

Plastic bottles have made staying hydrated easy, but studies show that heat changes what’s inside them. With small changes in storage habits and a shift toward safer materials, you can reduce your exposure to chemicals without sacrificing convenience, especially during the hotter months.