A Comprehensive Ecotoxicity Study of Molybdenum Disulfide Nanosheets versus Bulk form in Soil Organisms.

The increasing use of molybdenum disulfide (MoS 2 ) nanoparticles (NPs) raises concerns regarding their accumulation in soil ecosystems, with limited studies on their impact on soil organisms. Study aim: To unravel the effects of MoS 2 nanosheets (two-dimensional (2D) MoS 2 NPs) and bulk MoS 2 (156, 313, 625, 1250, 2500 mg/kg) on Enchytraeus crypticus and Folsomia candida . The organisms' survival and avoidance behavior remained unaffected by both forms, while reproduction and DNA integrity were impacted. For E. crypticus , the individual endpoint reproduction was more sensitive, increasing at lower concentrations of bulk MoS 2 and decreasing at higher ones and at 625 mg/kg of 2D MoS 2 NPs. For F. candida , the molecular endpoint DNA integrity was more impacted: 2500 mg/kg of bulk MoS 2 induced DNA damage after 2 days, with all concentrations inducing damage by day 7. 2D MoS 2 NPs induced DNA damage at 156 and 2500 mg/kg after 2 days, and at 1250 and 2500 mg/kg after 7 days. Despite affecting the same endpoints, bulk MoS 2 induced more effects than 2D MoS 2 NPs. Indeed, 2D MoS 2 NPs only inhibited E. crypticus reproduction at 625 mg/kg and induced fewer ( F. candida ) or no effects ( E. crypticus ) on DNA integrity. This study highlights the different responses of terrestrial organisms to 2D MoS 2 NPs versus bulk MoS 2 , reinforcing the importance of risk assessment when considering both forms.