Hazard profiling of compostable shopping bags. Towards an ecological risk assessment of littering

Littering represents an ecological threat. To date, studies have mainly focused on the formation and quantification of microplastics. Toxicity has generally been considered from the point of view of food safety rather than from an environmental viewpoint. There is an urgent need to develop a framework approach to assessing the ecological hazards associated with litter, particularly packaging litter. In fact, measuring the ecological impacts of packaging and single-use items is clearly a prerequisite for developing a control and mitigation strategy of accidental waste leakage. This study proposes a characterization methodology for the assessment of the ecological hazard of packaging and single-use items made with any material in the event of littering. This preliminary methodology is based on four aspects of ecological hazards: the migration of persistent ecotoxic chemicals by diffusion (type 1); the release of persistent ecotoxic chemicals after degradation (type 2); the physical persistence of the packaging (type 3); and the release of persistent micro-particles due to wear (type 4). A compostable shopping bag was tested using this classification in order to create a preliminary hazard profile. The bag released substances (6-7% of its mass) when soaked in water in less than three days. This leachate showed a high level of biodegradation and caused no adverse effects on germination and root development of cress seeds. The bag, tested according to the EN 13432 standard, does not cause ecotoxic effects after biodegradation when analysed with a plant growth test. The bag fragmented in soil and disappeared in 500 days. The bag, ground to microplastics, showed biodegradability when exposed to soil, with a half-life of 118 days.