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

Scott Winfield
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by Scott Winfield

When temperature rises, drinking water is the best way to stave off dehydration. But what about the water bottle that’s been rolling around the back seat of your car for weeks?

Is bottled water in a hot car safe to drink? 

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.

Is it Safe to Drink Bottled Water Left in Hot Car

Many people keep bottled water in their cars for various reasons. Some individuals like having bottled water on hand for emergencies, while others may forget their bottles inside the car. But what is the best practice if you decide to keep some bottles in your vehicle?

The FDA recommends storing bottled water in a car for no longer than a year (in the case of sparkling water) and two years for still water. However, this recommendation makes a critical assumption: that the water will remain at a cool temperature.

If you live somewhere hot, the guidelines change. In this case, the FDA recommends storing water in your car for two weeks or less.

Before we talk about why, you may be wondering how to safely keep a supply of water in your car. Your best bet is canned emergency water, which is readily available on Amazon and lasts up to fifty years at most temperatures. 

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, which is 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. BPA is also a likely human carcinogen, although the FDA finds it safe in small amounts

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

The Mayo Clinic was quick to assure consumers that small doses of BPA exposure are not a health hazard, and the FDA agreed. The International Bottled Water Association (IBWA) also stands behind the statements from both of these organizations.

Despite the words of caution from the authorities, it’s probably best to play it safe. Most experts recommend keeping plastic water bottles out of hot places like your car or garage. Instead, you should store water in a cool and dark storeroom, off the floor 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.

Leaving Water Bottles in Hot Car Is it Safe to Drink

An unopened bottle presents minimal risk, especially if the alternative is dehydration.

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 to more serious medical problems. 

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. Dump it out if so.

Does Bottled Water in Hot Car Cause Cancer?

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

People also claim that drinking water from a plastic bottle that has been frozen and reused 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–despite emails citing institutions like Johns Hopkins University or the Walter Reed Army Medical Center. The plastic used in water bottles has no dioxins, so you can put your cancer worries to bed.

What’s more, using plastic products is not associated with cancer. If you like to drink from plastic bottles and store food in plastic containers, you can continue to do so without worry.

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Scott Winfield
Scott Winfield
My name is Scott Winfield and researching and writing about water filters and other strategies to purify water has become my full time passion in recent years. I'm glad that you found our site and you can look forward to authoritative and well researched content here to help you get the best in water.
  1. that was a great article. worth reading. you have summarized the details in very simple words. thanks for the kind information’s.

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