Effects of soil and dietary exposures to Ag nanoparticles and AgNO 3 in the terrestrial isopod Porcellionides pruinosus Paula S. Tourinho a, * , Cornelis A.M. van Gestel b , Kerstin Jurkschat c , Amadeu M.V.M. Soares a , Susana Loureiro a a Department of Biology and the Centre for Environmental and Marine Studies, University of Aveiro, Aveiro, Portugal b Department of Ecological Science, Faculty of Earth and Life Sciences, VU University, Amsterdam, The Netherlands c Department of Materials, Oxford University, Begbroke Science Park, Begbroke Hill, Yarnton, Oxford, OX51PF, United Kingdom article info Article history: Received 30 March 2015 Received in revised form 28 May 2015 Accepted 29 May 2015 Available online Keywords: Toxicity Routes of exposure Silver nanoparticles Bioavailability abstract The effects of Ag-NPs and AgNO 3 on the isopod Porcellionides pruinosus were determined upon soil and dietary exposures. Isopods avoided Ag in soil, with EC50 values of ~16.0 and 14.0 mg Ag/kg for Ag-NPs and AgNO 3 , respectively. Feeding inhibition tests in soil showed EC50s for effects on consumption ratio of 127 and 56.7 mg Ag/kg, respectively. Although similar EC50s for effects on biomass were observed for nanoparticulate and ionic Ag (114 and 120 mg Ag/kg dry soil, respectively), at higher concentrations greater biomass loss was found for AgNO 3 . Upon dietary exposure, AgNO 3 was more toxic, with EC50 for effects on biomass change being >1500 and 233 mg Ag/kg for Ag-NPs and AgNO 3 , respectively. The difference in toxicity between Ag-NPs and AgNO 3 could not be explained from Ag body concentrations. This suggests that the relation between toxicity and bioavailability of Ag-NPs differs from that of ionic Ag in soils. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Silver nanoparticles (Ag-NPs) are widely used in the nanotech- nology industry and consumer products, especially due to their bactericidal properties. The production of Ag-NPs has increased in the last years, and it is one of the most produced NPs on the market (Meyer et al., 2009). Due to the release from NP-containing products, Ag-NPs may enter the aquatic environment and reach the soil through the land application of treated sewage sludge or biosolids (Gottschalk et al., 2009; Kaegi et al., 2011). In sewage sludge, the concentration was estimated to reach ~1.7 mg Ag/kg in Europe (Gottschalk et al., 2009). In biosolids-amended soils, however, much lower concen- trations are expected, although the continuous input of biosolids to agricultural land may lead to increasing Ag-NP concentrations over time. For example, an increase rate of 36 mg Ag/kg/y is estimated for agricultural land through sludge application in the United Kingdom (Whiteley et al., 2013). Modeled Ag-NP concentrations in soils exclusively treated with sludge ranged from ~10 to 100 mg/kg in Europe (Gottschalk et al., 2013). However, in sludge-free soils, estimated Ag-NP concentrations were 0.1e 1 mg/kg (Gottschalk et al., 2013). Toxicity studies on Ag-NPs in soil have shown that responses may occur at low levels of exposure. In a field experiment, effects of Ag-NPs on plants and microbial processes were found at concen- trations as low as 0.14 mg Ag/kg (Colman et al., 2013). And avoid- ance behavior of earthworms, measured as EC50, has been reported at ~4e8 mg Ag/kg in natural soil (Shoults-Wilson et al., 2011b). Up to date, dietary toxicity of NPs to isopods has previously been tested for Cu-NPs (Golobic et al., 2012), TiO 2 -NPs (Valant et al., 2012), ZnO-NPs (Pipan-Tkalec et al., 2010), and Ag-NPs (Tkalec et al., 2011). Only two studies have evaluated the effects of soil exposure on isopods for ZnO and CeO 2 -NPs (Tourinho et al., 2013, 2015). Previous studies with the isopod Porcellionides pruinosus have shown that different routes of exposure (i.e. food and soil) need to be evaluated to properly assess the effects of contaminants on isopods (Sousa et al., 2000; Vink et al., 1995). The objective of this study was to evaluate the toxicity of Ag-NPs and ionic Ag to the terrestrial isopod P. pruinosus, using soil and food as exposure routes. For this purpose, avoidance behavior and feeding inhibition were evaluated in natural soil spiked with Ag- NPs and ionic Ag (AgNO 3 ). Additionally, a feeding inhibition test * Corresponding author. E-mail address: paulatourinho@ua.pt (P.S. Tourinho). Contents lists available at ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol http://dx.doi.org/10.1016/j.envpol.2015.05.044 0269-7491/© 2015 Elsevier Ltd. All rights reserved. Environmental Pollution 205 (2015) 170e177