Abstract.The acute ecotoxicity of different diameters of silica and polyethyleneimine polystyrene (PS-PEI) nanoparticles (NPs) was assessed on a test battery of aquatic organisms representing different trophic levels. Daphnia magna, Thamnocephalus platyurus, Pseudokirchneriella subcapitata and Vibrio fischeri, were employed in a series of standard acute ecotoxicity tests and work was complemented with two cytotoxicological end points on a rainbow trout gonadal cell line (RTG-2). Physico-chemical characterization of the NPs was performed in the different test media employed, using dynamic light scattering (DLS) and zeta potentiometry. In contrast to silica NPs exposure, for which no effect was observed for concentrations up to 1000 µg ml -1 for all in vivo aquatic organisms tested, significant toxicity was detected after exposure to PS-PEI NPs at concentrations from 0.40 µg ml -1 to 416.5 µg ml -1.Differing sensitivities for each NP diameter for the different organisms was observed as: P. subcapitata > D. magna > T. platyurus > V. fischeri.The effects observed were dependent in some cases on the NP size, a higher effect being observed for the larger NPs. Finally, cytotoxicity studies showed an effect at the highest concentrations for both sets of NPs which was greater in the case of the PS-PEI NPs.However, as agglomeration and sedimentation of the nanoparticles was observed at these concentrations, the cytotoxicity studies were found not to be a reliable ecotoxicity test model.Keywords: Nanopolystyrene; Silica Nanoparticles; Ecotoxicity; Cytotoxicity.3 1 Introduction.The development of materials and products at the nanoscale has become a major investment area on a global level. Nanotechnology is largely based on these materials, generally defined as nanomaterials (NMs), which, for regulatory purposes, have been recently defined by the European Commission (EC) as any natural, incidental, or manufactured particulate material which is in the unbounded, aggregated or agglomerated form and with at least a 50 % of the particles in the number size distribution that has at least one dimension in the size between 1 and 100 nanometers (nm) (EC 2011). NPs fall within this definition, but to be more specific, NPs are defined as particulate materials with three dimensions of the order of 100 nm or less (Loevestam et al. 2010).NMs often exhibit enhanced or different properties when compared with the bulk material due to their extremely small size, consequent high specific surface area, surface energy and other factors such as larger proportions of under co-ordinated bonds and spatially constrained electronic wavefunctions (Lead and Wilkinson 2006). Certain NMs can offer, amongst others, distinct optical, electrical and magnetic properties, rendering them of great potential in a very wide range of fields and applications (Rao and Cheetham 2001). These, and other properties, make NMs very useful in technology and their use is rapidly increasing due to their applications in areas such as textiles, electronics, pharmaceutics, co...

Diflubenzuron and teflubenzuron are benzoylureas that are used in aquaculture to control sea lice. Flubenzurons have low toxicity to many marine species such as fish and algae but by their nature are likely to have significant adverse effects on nontarget species such as crustaceans and amphipods. Although the exact mechanism of toxicity is not known, these compounds are thought to inhibit the production of the enzyme chitin synthase during molting of immature stages of arthropods. These chitin synthesis inhibitors are effective against the larval and pre-adult life stages of sea lice. Due to their low solubility and results of recent monitoring studies conducted in Norway, the sediment compartment is considered the most likely reservoir for these compounds and possible remobilization from the sediment to benthic crustaceans could be of importance. For this reason, the epibenthic copepod Tisbe battagliai was selected for investigations into the acute and developmental effects of these compounds. For comparative purposes, azamethiphos was investigated to identify differences in sensitivity and act as a negative control for developmental effects at environmentally relevant concentrations. Standard acute studies with adult copepods showed little or no acute toxicity at milligrams per liter levels with the flubenzurons, whereas a naupliar developmental test demonstrated that environmentally relevant concentrations (e.g., nanograms per liter) caused a complete cessation of molting and finally death in the exposed copepods.

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In this study, a lab-scale wastewater treatment plant (WWTP), simulating biological treatment, received 10 μg/L Ag and 100 μg/L TiO nanoparticles (NPs) for 5 weeks. NP partitioning was evaluated by size fractionation (>0.7 μm, 0.1-0.7 μm, 3 kDa-0.1 μm, < 3 kDa) using inductively coupled plasma mass spectrometry (ICP-MS), single particle ICP-MS and transmission electron microscopy. The ecotoxicological effects of the transformed NPs in the effluent were assessed using a battery of marine and freshwater bioassays (algae and crustaceans) and an in vitro gill cell line model (RTgill-W1). TiO aggregates were detected in the effluent, whereas Ag NPs (0.1-0.22 μg/L) were associated with S, Cu, Zn. Fractionation showed that >80% of Ag and Ti were associated with the effluent solids. Increased toxicity was observed during weeks 2-3 and the effects were species-dependent; with marine epibenthic copepods and algae being the most sensitive. Increased reactive oxygen species formation was observed in vitro followed by an increase in epithelial permeability. The effluent affected the gill epithelium integrity in vitro and impacted defense pathways (upregulation of multixenobiotic resistance genes). To our knowledge, this is the first study to combine a lab-scale activated sludge WWTP with extensive characterization techniques and ecotoxicological assays to study the effects of transformed NPs in the effluent.

Silver, known for its antibacterial properties and for its toxicity to aquatic organisms, is one of the most frequently used nanomaterials and silver nanoparticles can be found in a range of consumer products as well as medical applications. The present study investigated the toxicity of three different nanomaterials (Mesosilver, NM300K and NM302) and AgNO 3 , in the algae Raphidocelis subcapitata. Exposures in the low µg L -1 range were combined with characterization of exposure media to determine whether differences in toxicity could be linked to changes in Ag speciation. All tested Ag compounds, except the NM302 Ag rods, reduced growth in the following order AgNO 3 ≥ M-Ag > NM300K > NM302 with 50 % effect concentrations of 7.09 (3.83-10.52), 9.7 (range not calculated) and 24.18 (15.66-98.16) µg L -1 , for AgNO 3 , Mesosilver and NM300K, respectively. Characterization of exposure media showed that both concentration and time influenced the speciation and stability of Ag in test media, regardless of Ag source, and also affected the toxicity to R. subcapitata. In both AgNO 3 and Mesosilver exposure the toxicity was correlated with the presence of Ag(I) (< 10 kDa), however levels of Ag(I) were too low to account for the observed Mesosilver effects, indicating a nanospecific contribution. Nanospecific toxicity was also observed for NM300K after 24 h of exposure, however the algae population recovered over time probably due to changes in exposure caused by aggregation of the nanoparticles.