Moreover, while some studies demonstrate that kd represents the mineralization of plastic to carbon dioxide, dissolution to dissolved organic carbon, or assimilation to biomass, 14 many studies present no evidence of complete or partial transformation. This poses challenges in knowing whether kd represents the chemical degradation (depolymerization) of the polymer or merely the physical degradation (disintegration) to microplastics. Regardless of the degradation process, the impacts of any degradation products released from plastic items must also be considered. Finally, a key challenge is that the molecular and microstructural features underpinning polymer degradation 46 also control many other polymer properties (e.g., Young's modulus). Of the studies reporting data sufficient to calculate kd, less than half included characterization of any physical and mechanical properties or provided enough details to determine them after the fact. Because the environmental lifetime of an item can depend on kd and other material properties, making effective material selection decisions will require reporting comprehensive details of material properties along with kd.