Researchers at Purdue University have...
Claims that plastic bottled water containers stored in warm environments (e.g., a hot automobile) “leach” unnamed chemicals that cause breast cancer or other maladies are not based in science and are unsubstantiated. There are no studies that prove this theory, instead, these allegations have been perpetuated by viral emails and media hype that only frighten and confuse consumers.
The U.S. Food and Drug Administration (FDA) comprehensively regulates the safety of foods and beverages, including bottled water. This includes a careful review of food and beverage packaging materials, including plastics, before allowing them on the market. With respect to leaving bottled water in a hot car, FDA has stated:
For approved plastics, FDA has found that the levels of migration to food of the substances due to the use of the plastics in contact with food are well within the margin of safety based on information available to the agency. This means no short or long-term health effects are likely to occur, even from life-long, daily dietary exposure to these substances migrating from plastic food-contact materials.
The International Bottled Water Association (IBWA) does urge consumers to handle and store bottled water containers with the same care and respect as they would any other food or beverage product.