Is It Safe To Drink Bottled Water Left In The Sun?

It's safe to assume that many people keep an emergency bottle of water or two on hand in their cars. Whether it's a busy afternoon that's left you parched or hours stuck in traffic that have you reaching for that bottle that's been rolling around on the backseat floorboard, you might want to rethink drinking it. While there have been many debates on the subject and information on whether or not it is safe to drink bottled water that has been left in the hot sun varies, there is a clear answer on the matter.

There have been two opposing forces presenting dialog on the safety of drinking from plastic water bottles that have been exposed to heat: the industry and its representation through the International Bottled Water Association and the scientists who study and research plastics. The voices from the industry claim that the water bottle companies test the safety of their products when exposed to heat and claim that their bottled water has been tested for safety after being left in hot cars and it is okay to consume. Plastics scientists, however, disagree.

Why you shouldn't drink bottled water exposed to heat

Scientists who specialize in plastics explain that the hotter a bottle of water gets, the more toxic chemicals inside of the plastics leak out into the water they hold. In fact, a 2008 study published in Water Research analyzed just how long a bottle of water can withstand heat before it reaches an unsafe level of toxic antimony that is used in plastic.

The study found that bottled water is safe in 70-degree Fahrenheit weather, but, during hotter days, that's not the case. When bottled water is exposed to extreme heat, such as the inside of a car on a summer day, it takes just over one month of exposure to that much heat for unsafe levels of antimony to be detected in the water.

Instead, try buying a bottle of water when you need it rather than leaving extra bottles in the sun for too long. You can also keep a reusable water bottle on hand so you can fill up whenever you need to without the risk of leaving water in the sun for extended periods of time.

Harmful bacteria can grow inside water bottles, too

Leaving an opened water bottle in the scorching heat, such as inside a hot car, can create a breeding ground for potentially harmful bacteria. The combination of warmth and exposure to air provides an ideal environment for microbial growth. Bacteria, including pathogenic strains, thrive in such conditions, multiplying rapidly and posing health risks if consumed. One harmful type of bacteria that can easily grow in such conditions is E. coli. 

To ensure the safety of your drinking water, it's crucial to store water bottles in a cool, shaded place away from direct sunlight and extreme heat. Always close the bottle cap tightly to minimize exposure to outside contaminants. Also, regularly clean and replace your water bottles to reduce the risk of bacterial growth and chemical leaching, ensuring that you stay hydrated with safe and refreshing water.

So, be sure to consume the water in your single-use plastic water bottles in a timely fashion — and change out the bottled water you keep in your car.