During the chemical process of polymerisation, bisphenol A (BPA) reacts and becomes firmly bound into the structure, thus actually building the polymer material. More than 99% of all BPA produced worldwide is converted into polymers.
Like with any chemical process, unavoidable trace levels of BPA (so-called free or residual BPA) can occur in the final polymer. The amount of free BPA in the polymer, however, does not play a key role in the question of BPA-migration. This is because in many cases the dominant mechanism responsible for the release of BPA from the polymer surface into the contacting aqueous liquid is hydrolysis, not the amount of free BPA monomer.
Several high quality migration studies on BPA, which included daily use conditions such as heating, microwaving, machine-dishwashing, rinsing, sterilising, have repeatedly shown that migration from BPA-based polycarbonate is very low and far below the safety levels set by the authorities. It does not pose a health risk to the consumer under normal handling and use of the products.
For example, a person weighing 60kg would have to consume every day of his/her entire life more than 300 l of water from a polycarbonate water dispenser, only to reach the level established as safe by the EFSA.
In fact, scientific studies have proved that trace amounts of BPA that might enter the human body are rapidly "metabolised" into an inactive kind of sugar, which is excreted from the body a day with no detrimental health effect.
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