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Clear guidance on conducting Environmental Risk Assessment (ERA) of nanomaterials is becoming more and more relevant as new applications of nanomaterials in the food and feed chain are developed. Upon request from EFSA, this report compiles and structures the relevant information for ERA of nanomaterials. This should support EFSA in preparing future guidance aimed at ERA of the application of nanoscience and nanotechnology in the food and feed chain. Existing ERA guidance documents were analysed for their adequacy to cover issues that are specific for nanomaterials, e.g. related to nanospecific behaviour. Each nanospecific issue was addressed by briefly reviewing the existing methods to address the issue in each separate step of ERA. In exposure assessment adaptations are needed in current approaches because nanomaterial behaviour and fate are not described by equilibrium partitioning and certain nanomaterial specific fate processes are not included in existing modelling tools and derivation of default values. In hazard and risk characterisation the main adaptations are needed in metrology and dose metrics by adequately describing the fate and behaviour of nanomaterials in exposure media. These adaptations are needed to address the issue of specific uptake mechanisms and bioavailability of nanomaterials, and the impact of nanospecific behaviour on the outcome of (chronic) toxicity studies. Furthermore, relevance of test species should be considered in relation to expected fate of a nanomaterial application in the environment. Overall, collaboration with other EU agencies (e.g. ECHA, EMA) and organisations on method developments (e.g. OECD, ISO) is advised to avoid duplication of work and contradictory recommendations in ERA guidance for nanomaterials. [ABSTRACT FROM AUTHOR]

The present study investigated how humic substances (HS) modify the aquatic toxicity of silver nanoparticles (AgNPs) as these particles agglomerate in water and interact with HS. An alga species ( Raphidocelis subcapitata), a cladoceran species ( Chydorus sphaericus), and a freshwater fish larva ( Danio rerio), representing organisms of different trophic levels, were exposed to colloids of the polyvinylpyrrolidone-coated AgNPs in the presence and absence of HS. Results show that the presence of HS alleviated the aquatic toxicity of the AgNP colloids to all the organisms in a dose-dependent manner. The particle size distribution of the AgNPs' colloidal particles shifted to lower values due to the presence of HS, implying that the decrease in the toxicity of the AgNP colloids cannot be explained by the variation of agglomeration size. The surface charge of the AgNPs was found to be more negative in the presence of high concentrations of HS, suggesting an electrostatic barrier by which HS might limit interactions between particles and algae cells; indeed, this effect reduced the algae toxicity. Observations on silver ions (Ag+) release show that HS inhibit AgNP dissolution, depending on the concentrations of HS. When toxic effects were expressed as a function of each Ag-species, toxicity of the free Ag+ was found to be much higher than that of the agglomerated particles. Environ Toxicol Chem 2015;34:1239-1245. © 2015 SETAC [ABSTRACT FROM AUTHOR]

Sedimentation of engineered nanoparticles (ENPs) has been studied mainly in artificial media and stagnant systems mimicking natural waters. This neglects the role of turbulence and heteroaggregation with sediment. The authors studied the apparent sedimentation rates of selected ENPs (cerium dioxide [CeO2], polyvinylpyrrolidone-capped silver [PVP-Ag], and silica-coated silver [SiO2-Ag]) in agitated sediment-water systems resembling fresh, estuarine, and marine waters. Experiments were designed to mimic low energy and periodically resuspended sediment water systems (14 d), followed by a long-term aging, resuspension, and settling phase (6 months), as would occur in receiving shallow lakes. The ENPs in systems with periodical resuspension of sediment were removed with sedimentation rates between 0.14 m/d and 0.50 m/d. The sedimentation rates did not vary much among ENP type, salinity, and aging time, which is attributed to the capture of ENPs in sediment flocks. The sedimentation rates were 1 to 2 orders of magnitude higher than those reported for aggregation-sedimentation in stagnant systems without suspended sediment. Heteroaggregation rates were estimated and ranged between 0.151 L/mg/d and 0.547 L/mg/d, which is up to 29 times higher than those reported for natural colloids under quiescent settling conditions. The authors conclude that rapid scavenging and sedimentation drives removal of ENPs from the water column. Environ Toxicol Chem 2014;33:1766-1773. © 2014 SETAC [ABSTRACT FROM AUTHOR]

Estimating the environmental exposure to manufactured nanomaterials is part of risk assessment. Because nanoparticles aggregate with each other (homoaggregation) and with other particles (heteroaggregation), the main route of the removal of most nanoparticles from water is aggregation, followed by sedimentation. The authors used water samples from two rivers in Europe, the Rhine and the Meuse. To distinguish between small (mainly natural organic matter [NOM]) particles and the remainder of the natural colloids present, both filtered and unfiltered river water was used to prepare the particle suspensions. The results show that the removal of nanoparticles from natural river water follows first-order kinetics toward a residual concentration. This was measured in river water with less than 1 mg L−1 CeO2 nanoparticles. The authors inferred that the heteroaggregation with or deposition onto the solid fraction of natural colloids was the main mechanism causing sedimentation in relation to homoaggregation. In contrast, the NOM fraction in filtered river water stabilized the residual nanoparticles against further sedimentation for up to 12 d. In 10 mg L−1 and 100 mg L−1 CeO2 nanoparticle suspensions, homoaggregation is likely the main mechanism leading to sedimentation. The proposed model could form the basis for improved exposure assessment for nanomaterials. Environ. Toxicol. Chem. 2012; 31: 1019-1022. © 2012 SETAC [ABSTRACT FROM AUTHOR]