Don’t leave your water bottles in a hot car! You’ll get breast cancer! That’s the warning that has been circulating on the web ever since singer Sheryl Crow appeared on the Ellen DeGeneres show and discussed her breast cancer. She didn't actually say that her breast cancer was caused by having left water bottles in a car. And what if she had? Is Sheryl an icon of science? Hardly. Unfortunately Sheryl was diagnosed with breast cancer and when such a calamity occurs people commonly look for possible causes of their affliction. The lay press is filled with articles demonizing plastics, mostly in an unjustified fashion, and Sheryl likely heard about chemicals like bisphenol A and the phthalates that have been accused of causing cancer. Neither of these is present in the kind of water bottles Sheryl was concerned about. Bisphenol A is used to make polycarbonate plastics which are used in the large carboys that sit on top of water coolers but not in the commonly used water bottles which are made of polyester. And here some confusion about phthalates enters the picture.
One of the chemicals used to make polyester is terephthalic acid. There could conceivably be trace amounts of this that leach into the water. The “hot car” connection comes from the correct notion that an increase in temperature increases the leaching of water-soluble compounds from plastic. But terephtalic acid is not the phthalate that has been implicated by some in health problems. That is diethylhexylphthalate, a chemical added to some plastics, mostly to polyvinyl chloride (PVC), to increase their flexibility. The only PVC used in water bottles is in the cap, any leaching from that would be trivial. And it needs to be emphasized that there is no credible evidence that bisphenol A or phthalates play a role in breast cancer.
Sadly Sheryl Crow now has been diagnosed with a brain tumour. She wonders whether this was caused by her use of a cell phone. Not according to the vast majority of studies. Cancer is a terrible disease and in most cases the cause is unknown, which of course opens the door to all sorts of speculation. I think bottled water should be shunned. But not because of any cancer connection. It is an environmental disaster. Only a small percentage of the bottles are recycled and using valuable petroleum resources to make bottles that are totally unnecessary is foolish. But the bottled water industry has done a wonderful job convincing the public that they need to pay for something that is widely available for free.