Leaving Plastic Water Bottles in the Sun: Is it Safe?
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Leaving Water Bottles in the Sun: Is it Safe?

The chemicals used to manufacture our bottled water leads some to worry. Can the heat of the sun break down the plastic and make the water unsafe? Should you search for a cool, shady spot for your drink?

What Happens to a Water Bottle in the Sun?

Water bottles contain a soft kind of plastic named polyethylene terephthalate, or PET. Governing regulations set by the U.S. Food & Drug Administration and the Environmental Protection Agency ensure that the market’s bottled beverages — their liquids and containers — are safe for humans.

When water bottles warm up from sunlight, you may notice a slight change in the water’s taste, smell or color, but generally, the change isn’t a sign that the water has been contaminated.

study published in 2014 found that over time, a warmer storage environment than normal can leach trace amounts of antimony, a hard metal, from PET water bottles. However, all but one of the 16 brands tested still had safe levels of the substance.

Another measurement conducted in the same study was of bisphenol A (BPA), a chemical compound used in household products and containers for our food and beverages. While BPA was slightly higher in the tests as well, it didn’t exceed the EPA’s regulatory guidelines. Researchers are still investigating the effects of BPA exposure on the body, but you can look for BPA-free labeling on the packaging before you buy something if you’re concerned about ingestion.

Some old claims have also been debunked, including that the heating or freezing of disposable PET water bottles introduced a suspected carcinogen called di-ethylhexyl adipate (DEHA) into the water. The overall consensus is that it’s safe and healthy to crack open a warm water bottle — even if it won’t be quite as refreshing.

Is It Safe to Drink Bottled Water Left in the Sun?

The safety of bottled water in the sun is quite stable for shorter periods. The 2014 study found over four weeks that as exposure lengthens, chemicals increase but level out before they become unsafe.

The one location your plastic water bottle should avoid sitting for long is inside a hot car. On a clear, summer day, the sun’s concentrated rays through your car window — coupled with a warmed vinyl seat — can heat the surfaces beneath a container to over 200 degrees Fahrenheit. In 2017, a viral video shared an Idaho battery technician’s warning after he noticed his plastic bottle smoking beside him. In short, leaving water bottles in the car poses a rare but very real fire risk.

Can Bacteria Grow Inside Water Bottles?

Once a bottle has been opened, there’s a chance that airborne microbes can cling to the inside of the mouthpiece. Not every species of bacteria is a serious health risk, but after a few days, the trapped humidity in a warm, closed, near-empty bottle can breed new organisms. Fortunately, it’s harmless to refill your water bottle multiple times as long as you rinse it with hot, soapy water and let it dry out uncapped.

A good rule of thumb is to store your bottled water out of the sun to preserve its look and flavor. Warmth will cause only slight alterations to the water’s composition.

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Contact Polymer Solutions International for Securing Your Water Bottles

At PSI, we’re experts in providing safe, hygienic storage of bottled water for many commercial industries. To learn more about our services and solutions, call 610-325-7500 or contact us online today.


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