Leaving a plastic water bottle in a hot car might seem harmless, but it can pose several health risks. When exposed to high temperatures, plastic bottles can leach chemicals into the water they contain. Temperatures above 85°F (29°C) can trigger this chemical release, and the higher the heat, the faster the process occurs. These chemicals, such as Bisphenol A (BPA) and phthalates, are known endocrine disruptors, which can interfere with hormones and potentially lead to various health issues over time.