Earthworm avoidance of silver nanomaterials over time.

Avoidance behaviour offers a highly relevant information as it reveals the ability to avoid (or not) possible toxic compounds in the field, hence it provides information on reasons for the presence/absence in the field. The earthworm Eisenia fetida was used to study avoidance behaviour to four silver forms (three nanomaterials (NMs) and one salt) over four time points (24, 48, 72 and 96 h), using OECD standard soil. Avoidance behaviour depended on both exposure material and concentration, but in general changed little with exposure duration. Avoidance was highest for the salt (AgNO3) for all exposure durations and showed a continuous higher avoidance with time (based on EC50 values). The AgNMs avoidance was in the order NM300K<AgNM-non coated = AgNM- PVP coated. It was not possible to identify one soil solution fraction that correlated with EC50 across materials.