Water Bottles In Cars Cause Cancer?

Myth: Drinking from a plastic water bottle left in a hot car can cause cancer.

Fact: This rumor falsely claims that dioxins—a group of toxic chemicals associated with an array of health problems, including breast cancer—leach from the heated plastic into the water.

Plastics do not contain dioxins, and the sun's rays are not strong enough to create them, says Michael Trush, PhD, deputy director of the Johns Hopkins Center for Urban Environmental Health. Most single-use beverage bottles sold in the United States are made from polyethylene terephthalate (PET), a substance tested extensively for safety. There is some evidence that heat can cause bisphenol A (BPA), a compound that's been shown to have estrogenic effects in animal studies, to leach from plastic bottles into the water. (The "estrogenic effects" are thought to impact cancer risk.) However, most single-use water bottles sold in the United States are made from BPA-free plastic. And there's no proven link to breast cancer in women anyway. To be safe, drink from a reusable plastic bottle labeled "BPA free," or choose water bottles with a "1," "2," "4," or "5" in the recycling symbol on the bottom. 

Published November 2011, Prevention