Abstract
Biodegradable plastics are mostly applied in packaging materials (e.g. shopping bags), waste collection bags, catering products, and agricultural applications. In this last case, degradation takes place directly in soil where biodegradable plastic products are intentionally left after use (e.g. mulch films for weeds control). Due to the growing volumes of biodegradable polymers and plastics, interest in their environmental safety is increasing and more research is carried out. Some attempt has been made to apply biotests, used in other sectors of environmental sciences, in the assessment of biodegradable plastics safety. In this work, the quality of soils after biodegradation of the bioplastics Mater-Bi has been assessed with a large array of biotests based on model organisms representative of the different trophic levels in the food chains of the edaphic and aquatic ecosystems. Mater-Bi was degraded under controlled conditions for 6 months at a 1% concentration. The selected organisms included bacteria and protozoa (V. fischeri and D. discoideum, respectively), the green alga P. subcapitata, plants (the monocotyledon S. saccharatum and the dicotyledon L. sativum), and invertebrates animals (D. magna, a freshwater crustacean, and the Oligochaeta earthworm E. andrei), using both acute and chronic endpoints. The results of the applied ecotoxicological tests showed that the Mater-Bi materials tested at very high doses did not affect the soil quality. Soil exposed to Mater-Bi has no noxious effects on edaphic organisms; in particular, mono and dicotyledon plants results, indicate that Mater-Bi plastic products are innocuous for agricultural uses. The use of more sensitive chronic endpoints allows to exclude possible effects at population level. This is the first time that such a comprehensive approach is applied to the assessment of possible ecotoxicity effects induced by biodegradable plastics in soil and represents a possible starting point for improved standardized testing schemes.
Highlights
Biodegradable plastics are mostly applied in packaging materials, waste collection bags, catering products, and agricultural applications (Shen et al, 2009)
A sample of the matrix is tested with biotests for ecotoxicity together with a control sample not exposed to the plastic item and a control sample exposed to a GRAS (Generally Recognized As Safe) substance, such as cellulose
With respect to lab control, for the amebae exposed to the elutriates of the soil RIC 1620 (Mater-Bi containing soil) and of the cellulose soil; the effects never reach the decrease of 20% with respect to the lab controls, a value usually considered as an indication of weak toxicity
Summary
Biodegradable plastics are mostly applied in packaging materials (e.g., shopping bags), waste collection bags, catering products, and agricultural applications (Shen et al, 2009). Degradation can take place directly in soil where biodegradable plastic products are intentionally left after use (e.g., mulch films for weeds control). That is why all the testing protocols developed to characterize the biodegradable plastics and packaging include the assessment of ecotoxicity potentially originated from the biodegradation. Standards have been developed to specify the requirements for biodegradable plastics and packaging in composting (i.e., organic recycling), in home composting, and in soil. The testing approach is similar in all cases: the plastic material is exposed to the matrix of interest (e.g., compost, soil) in a very high dose and let biodegrade. No significant difference must be found between the test samples and control samples
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