Detection of toxicity released by biodegradable plastics after composting in activated vermiculite

The composting test method based on activated vermiculite is a comprehensiv e system for the assessment of the environmental impact of biodegradable pl astics. It allows, in a single test, (i) the measurement of the mineralizat ion of the polymer under study; (ii) the retrieval of the final polymeric r esidues and (iii) determination of the biomass (to make a final mass balanc e); (iv) detection of breakdown products of the original polymer. In this s tudy it is shown that the vermiculite test method is also suitable to perfo rm ecotoxicological studies. The Flash test is a method based on kinetic me asurement of bioluminescence by Vibrio fischeri, and was applied to evaluat e the toxicity of compost samples and vermiculite samples after the biodegr adation of a polyurethane (PU) based plastic material. Toxicity was detecte d in vermiculite samples contaminated by 4,4 ' diamino diphenyl methane (MD A), a toxic breakdown product released by the PU moiety, as shown by HPLC. On the other hand, neither toxicity nor the presence of MDA was detected in mature compost. A recovery experiment previously performed had shown a 10% MDA recovery yield from mature compost. The possibility of testing the eco toxicity of extracts obtained from mineral matrix after biodegradation make s the vermiculite test system particularly interesting for the overall asse ssment of the environmental impact of biodegradable plastics. (C) 2001 Else vier Science Ltd. All rights reserved.