Multigenerational toxicity of microplastics derived from two types of agricultural mulching films to Folsomia candida

Degradation and fragmentation of mulching films represents an increasing source of microplastics (MPs, plastic particles 1 μm to 5 mm in size) to agricultural soils. MPs have been shown to affect many soil invertebrates, including springtails. However, these studies typically use test materials representing less environmentally relevant particle types, such as pristine uniform MPs, which do not represent the large range of particle sizes and morphologies found in the field. This study aimed at providing insight into the adverse effects of MPs originating from agricultural mulching films, by using artificially aged MPs derived from both biodegradable (starch-polybutadiene adipate terephthalate (PBAT)) blend, as well as conventional (linear low-density polyethylene (LLDPE)) plastic polymers. The soil dwelling springtail Folsomia candida was exposed to these MPs for five generations in order to elucidate population effects due to possible reproduction toxicity, endocrine disruption, mutagenesis or developmental toxicity. F. candida were exposed to 0, 0.0016, 0.008, 0.04, 0.2, 1, 2, 3, 4 and 5 % (w/w dry soil) MPs in Lufa 2.2 soil, which includes concentrations within the range of environmental relevance. Juveniles produced at each concentration were transferred to the next generation, with the parental, F2 and F4 generations being exposed for four weeks and F1 and F3 generations for five weeks. No concentration-dependent effects on F. candida survival or reproduction were observed in exposures to either of the MPs, in any of the generations. These results suggest that the particular MPs used in this study, derived from mulching films used on agricultural soils, may not be potent toxicants to F. candida, even after long-term exposure and at elevated concentrations.