Release of bisphenol A from polycarbonate baby bottles: water hardness as the most relevant factor

The concentrations of bisphenol A (BPA) in the content of polycarbonate baby bottles reported by scientific literature were almost always clearly below 1 μg/l, but in a German consumer journal they reached 157 μg/l. These high values were interpreted as a result of microwave heating, but here they are shown to be the result of testing with tap water. Since BPA is primarily released by degradation of the polycarbonate, rather than by migration from the polymer, testing with food simulants (distilled water or distilled water/ethanol) is not appropriate. Degassing of tap water during boiling causes the pH to increase and the water to become more aggressive. BPA concentrations may reach 50 μg/l if a polycarbonate bottle is sterilized by boiling water in it (well feasible only by means of microwave heating) and this same water is used to prepare a beverage. Increased concentrations are also observed when boiling-hot beverages with a high pH are filled into the bottle, such as boiled plain water or tea. Respecting simple rules, the BPA concentrations can be kept below 0.5 μg/l.