Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

Current bioavailability models, such as the free ion activity model and biotic ligand model, explicitly consider that metal exposure will be mainly to the dissolved metal in ionic form. With the rise of nanotechnology products and the increasing release of metal-based nanoparticles (NPs) to the environment, such models may increasingly be applied to support risk assessment. It is not immediately clear, however, whether the assumption of metal ion exposure will be relevant for NPs. Using an established approach of oral gluing, a toxicokinetics study was conducted to investigate the routes of silver nanoparticles (AgNPs) and Ag(+) ion uptake in the soil-dwelling earthworm Lumbricus rubellus. The results indicated that a significant part of the Ag uptake in the earthworms is through oral/gut uptake for both Ag(+) ions and NPs. Thus, sealing the mouth reduced Ag uptake by between 40% and 75%. An X-ray analysis of the internal distribution of Ag in transverse sections confirmed the presence of increased Ag concentrations in exposed earthworm tissues. For the AgNPs but not the Ag(+) ions, high concentrations were associated with the gut wall, liver-like chloragogenous tissue, and nephridia, which suggest a pathway for AgNP uptake, detoxification, and excretion via these organs. Overall, the results indicate that Ag in the ionic and NP forms is assimilated and internally distributed in earthworms and that this uptake occurs predominantly via the gut epithelium and less so via the body wall. The importance of oral exposure questions the application of current metal bioavailability models, which implicitly consider that the dominant route of exposure is via the soil solution, for bioavailability assessment and modeling of metal-based NPs.

Original publication

DOI

10.1002/etc.3036

Type

Journal article

Journal

Environ Toxicol Chem

Publication Date

10/2015

Volume

34

Pages

2263 - 2270

Keywords

Exposure route, Nanoparticles, Silver, Uptake, X-ray absorption near-edge spectroscopy, Animals, Biological Availability, Ions, Metal Nanoparticles, Oligochaeta, Risk Assessment, Silver, Soil Pollutants, Tissue Distribution, X-Ray Absorption Spectroscopy