It is well recognized that PCL undergoes hydrolytic degradation and consequently releases breakdown products, implying that breakdown products could be the dominating source of the observed toxicity and bioactivity. As with nanoplastics, oligomers are increasingly being recognized as chemicals of concern for human health and the environment. Tamayo-Belda et al. demonstrated that consumer-grade PCL pellets shed appreciable quantities of nanoplastics (1.70.1 mg/g pellet; 210 9 particles/g pellet; mean diameter 6715 nm), small microplastics (0.70.2 mg/g pellet; diameter 100-1000 nm), and linear and cyclic oligomers (0.30.1 mg/g pellet) within 1 day of incubation in 1 mM potassium phosphate buffer at pH 7 and ~28 ºC.