Migration of BPA was also shown to be increasing with time and temperature . According to , the correlation between the migration of BPA and time which varied between 32 -55 ng/mL (on day 1) to 228-516 ng/mL (on day 6) corresponds to a second-degree polynomial (Migration = at 2 + bt + c) when tested with water at 1-6 days at 70 °C . Noted by the authors, the emergence of this variation in BPA migrated between samples may largely be due to different levels of residual BPA in the samples .