Leaving Water Bottles in Hot Car: Is it Safe to Drink?

When we’re thirsty, we reach for the closest water bottle around. But what if that bottle has been rolling around the back seat of your car for weeks?

Is bottled water that has remained a long time in a hot car safe to drink? We’ll answer this question and more below.

Is It Bad to Leave Water Bottles in the Car?

Even though experts warn against keeping disposable plastic water bottle in a hot car, nothing terrible is likely to happen if you do so.

Many people keep bottled water in their cars for various reasons. Some individuals like having bottled water on hand for emergencies, while others may simply forget it inside the car.

Luckily for them, the FDA doesn’t have any specific recommendations about keeping water bottles in hot temperatures. So, what they’re doing isn’t officially bad.

However, that shouldn’t mean it’s completely fine either, as plastic tends to react badly to heat. Moreover, subjectively speaking, water that’s remained too long in heat won’t taste great.

What Happens When Plastic Water Bottles Get Hot?

Plastic is made from polymers. These chemical-bonded molecules begin to break down when heated, which can allow chemicals in the plastic to leach into the water.

A popular 2014 study explains the phenomenon. After four weeks at 158 degrees Fahrenheit, researchers found that some antimony and bisphenol A (BPA) had leached into the water.

Antimony, used to manufacture plastic, can be toxic in high doses. BPA makes plastic bottles tough and glossy, but it has been deemed an endocrine disruptor as well as a potential human carcinogen.

While the study made alarming discoveries, it’s critical to note that it looked at sixteen different water brands. Of these sixteen, only one had BPA levels above EPA regulations with trace amounts of antimony. Moreover, the FDA finds BPA safe in small amounts.

Still, it’s probably best to play it safe. Most experts recommend keeping plastic water bottles out of hot places like your car or garage. You should store them in a cool, dark place and away from heat sources.

An Unintended Consequence of Storing Water Bottles in Hot Car

There’s another reason you should be careful with leaving plastic water bottles in the car –likely one that never crossed your mind. In the right conditions, you may start a small fire!

The sun’s powerful rays have lots of energy; enough to channel light into a high-powered magnifying glass, using the water bottle as a lens. In the right conditions, this beam could cause a car’s upholstery to burn.

While most vehicles are manufactured with fire-retardant materials, your water bottle can be enough to leave some serious burn marks.

Is it Safe to Drink Bottled Water Left in Hot Car?

Occasionally drinking forgotten bottled water in a hot car is unlikely to have any serious health effects. However, it’s critical to distinguish between opened and unopened bottles.

An unopened bottle presents minimal risk, but you should avoid drinking from a water bottle that’s been opened and then left in a hot space. Hot vehicles provide the perfect breeding ground for bacteria to grow, so it’s best to toss any opened bottles left in your car. 

Does Bottled Water Go Bad in Heat?

It’s vital to understand that water itself doesn’t go bad. When stored properly, bottled water lasts quite a long time. There is no limit on the shelf life of water, which is why the FDA doesn’t require bottled water products to carry an expiration date. 

What does deteriorate and “go bad” in the heat is the container, which we discussed above. When heat affects the bottle, it can cause mild effects, like changes in flavor or smell, as well as more serious medical problems like increased blood pressure due to potential BPA contamination.

To prevent heat damage to your water, it’s best to store bottles in a cool place. The ideal temperature is between 50 and 70 degrees Fahrenheit, though extreme cold can damage water bottles too. 

For most people, it’s pretty easy to tell if something’s off with your water. If there is a contaminant present, you are likely to notice a strange taste or smell.

Does Bottled Water in Hot Car Cause Cancer?

You may have heard this claim, which has circulated unchecked on the internet for many years, but drinking bottled water in a hot car does not cause cancer.

People also claim that drinking water from a frozen plastic bottle causes cancer. The reasoning is that heating and freezing plastic bottles releases chemicals that might cause cancer, like dioxins.

Fortunately, there are no studies to back up these claims. The plastic in water bottles has no dioxins, so you can put your cancer worries to bed.

Moreover, using plastic products isn’t associated with cancer since the BPA amount that might leach from them is pretty low compared to carcinogen levels, as stated by the FDA. If you like to drink from plastic bottles and store food in plastic containers, you can continue to do so without worry.

Conclusion

Most water bottles are made of plastics. While the reaction between heat and plastic can cause hazardous contaminants like BPA to leach into the water, it’s improbable that the BPA levels will reach dangerous levels. So, there’s little or no risk associated with drinking water from a bottle that’s been left in a hot car.