On the lifespan of Enchytraeus crypticus - impact of iron (nanomaterial and salt) on aging

Iron oxide nanomaterials (Fe₃O₄ NMs) have important biomedical and environmental applications, e.g. drug delivery, chemotherapy, magnetic resonance imaging contrast agents, etc. However, the environmental risks of such Fe₃O₄ are not fully assessed, particularly for soil living invertebrates, which are among the ones in the first line of exposure. Research has showed that longer-term exposure time is required to assess hazards of NMs, not predicted when based on shorter time and are therefore recommended. Thus, in the present study the effects of Fe₃O₄ NMs and FeCl₃ were assessed in the terrestrial environment, using the soil model species <i>Enchytraeus crypticus</i> (Oligochaeta), throughout its entire lifespan (202 days). Two animals' density were used: 1 (D1) and 40 (D40) animals per replicate, in LUFA 2.2 soil. The endpoints were survival and reproduction monitored over-time, up to 202 days. Results showed that density clearly affected the toxicity response, with higher toxicity and lower lifespan in D1 compared to D40. Overall, FeCl₃ was more toxic than Fe₃O₄ NM in terms of reproduction, however, adult animals can be at higher (long-term) risk when exposed to Fe₃O₄ NM. Differences might be linked to slower Fe kinetics for the Fe₃O₄ NMs, i.e., slower Fe dissolution and release of ions.