Identification and characterization of single use oxo/biodegradable plastics from Mexico City, Mexico: Is the advertised labeling useful?

The compositional characterization of single-use plastics (SUPs), often advertised as biodegradable (B) and oxo-biodegradable (OB), is an important step towards plastic pollution mitigation through the formulation of appropriate (re) use and disposal strategies. We present here the very first study to screen daily SUPs in Mexico through comprehensive characterizations of 33 randomly collected samples (B and OB) of high consumption, with or without food contact, from the markets (n = 80), bakeries (n = 5), pharmacies (n = 5) and near public transportation systems (n = 2) across 16 municipalities of Mexico City, using the polymer composition, metal contents and thermal properties. These SUPs are composed of 85% high-density polyethylene and 15% low-density polyethylene, with significant inorganic additives, and all of them show variable thermal degradation behavior. Among the twenty five different metals identified, most of the SUPs exceed the standard international norms (94/62/EC; EN 13432; 2016/1416; ASTM D6400-04) for Cu, Cr, Mo, Zn, Fe and Pb with the maximum concentrations of 1898 mg/kg, 1586 mg/kg, 95 mg/kg, 1492 mg/kg, 1900 mg/kg and 7528 mg/kg, respectively. Our findings uncovered that the collected SUPs from Mexico City did not have the suitable physicochemical characteristics and they might end up adding to the exponentially growing solid waste in the immediate future. Hence, we recommend the implementation of strict norms to certify the SUPs.