Additives in bioplastics: Chemical characterization, migration in water and effects on photosynthetic organisms

The potential release in the environment and biological effects of chemicals like additives and non-intentionally added substances present in conventional plastics and bioplastics is an issue that could occur if these materials are not properly disposed of. Herein, seven leachates of biobased and biodegradable plastics made of polylactic acid (PLA), polybutylene succinate (PBS)/PLA blends, and starch-based blends (SB) were characterized and compared for the inorganic and organic additives present in the source materials. The main inorganic elements found in the leachates were Na, Mg, K, and Ca (0.1-100 mg L^-1), corresponding to the main elements present in the bioplastics. Also trace elements such as Ba, Zn, Sr, B, Fe, Ti, Al, Mn, Cu, and Sn occurred in leachates with concentrations between 1 and 1000 μg L^-1. In contrast, most of the organic additives found in the bioplastics did not migrate in water and the few organic compounds detected and identified were not of concern. The lowest tested concentration of PBS/PLA- and SB-leachates (0.5 % of the corresponding initial leachate) induced a significant algal growth inhibition (corresponding to bioplastic concentrations in water of 0.4 g L^-1). Conversely, PLA-based materials were less toxic (LOEC corresponding to 10 % of the leachates or >75 %). No effect on seed germination nor the development of roots and shoots of cress was observed for any leachate prepared from PLA and PBS/PLA materials. Leachates prepared from SB bags inhibited the growth of roots and shoots at the concentrations of 25 and 50 %, while they induced hormesis at 10 % concentration promoting a growth higher than the control.