Release of bisphenol A from polycarbonate baby bottles: mechanisms of formation and investigation of worst case scenarios

The question was further investigated whether there could be conditions resulting in contamination of beverages in polycarbonate bottles for babies with bisphenol A (BPA) at concentrations causing the tolerable daily intake (TDI) to be approached or exceeded. It is a follow up of previous work showing increased release of BPA after extended use of the bottles. Migration in the proper sense was low, but larger amounts of BPA were observed from degradation of the polycarbonate. Since there are no standardized testing conditions to determine release by degradation of the polymer, worst case scenarios were investigated. Alkali washing solutions at concentrations typical for dishwashers contained BPA in concentrations little above 100 mu g/l. In reality they are diluted in the general washing liquid and finally poured out. Drying was the most critical step, particularly after inadequate rinsing of bottles, when alkali detergent was "baked" to the bottle wall at elevated temperature. BPA thus formed is transferred into the beverage, but is unlikely to exceed 10 mu g/l. The highest transfer into the beverage (up to about 500 mu g/l) could occur when the bottle is positioned in the dishwasher at such inclination that the detergent solution does not fully run off and is poorly rinsed, but this scenario is unlikely to often occur. In conclusion, even rather extreme scenarios do not result in BPA contamination near to the level corresponding to the TDI.