Natural degradation of APAP in the positive control was less than 1% after 48 h, demonstrating the stability of the compound in aqueous solutions and the refore the environment. Fig. 3 A depicts the APAP concentration in the exposure media over time. After 24 h,72+7% of the initial APAP exposure concentration remained in the media and after 48 h 56+7% for the various ball numbers.