Imaging of engineered nanoparticles and their aggregates under fully liquid conditions in environmental matrices.

The increasing industrial production of engineered nanoparticles (ENPs) raises concern over their safety to humans and the environment. There is a lack of knowledge regarding the environmental fate and impact of ENPs and in situ methods are needed to investigate e.g. nanoparticle aggregation and adsorption in the media of concern such as water, sediment and soil. In this study, the application of wet scanning electron microscopy (WetSEM) technology in combination with energy dispersive x-ray spectroscopy (EDS) to visualise and elementally identify metal and metal oxide nanoparticles (Au, TiO(2), ZnO and Fe(2)O(3)) under fully liquid conditions in distilled and lake water as well as in a soil suspension has been investigated. WetSEM capsules comprise an electron transparent membrane enabling the imaging and EDS analysis of liquid samples. Results are compared with conventional SEM images and show that WetSEM/EDS is a promising complementary tool for the in situ investigation of ENPs and their aggregates in natural matrices. In combination with other analytical tools (e.g. HDC- or FFF-ICP-MS, DLS), WetSEM could help to provide a better understanding of the fate and behaviour of ENPs in the environment.

Detection and characterization of engineered nanoparticles in food and the environment.

Nanotechnology is developing rapidly and, in the future, it is expected that increasingly more products will contain some sort of nanomaterial. However, to date, little is known about the occurrence, fate and toxicity of nanoparticles. The limitations in our knowledge are partly due to the lack of methodology for the detection and characterisation of engineered nanoparticles in complex matrices, i.e. water, soil or food. This review provides an overview of the characteristics of nanoparticles that could affect their behaviour and toxicity, as well as techniques available for their determination. Important properties include size, shape, surface properties, aggregation state, solubility, structure and chemical composition. Methods have been developed for natural or engineered nanomaterials in simple matrices, which could be optimized to provide the necessary information, including microscopy, chromatography, spectroscopy, centrifugation, as well as filtration and related techniques. A combination of these is often required. A number of challenges will arise when analysing environmental and food materials, including extraction challenges, the presence of analytical artifacts caused by sample preparation, problems of distinction between natural and engineered nanoparticles and lack of reference materials. Future work should focus on addressing these challenges.

Probabilistic risk assessment for linear alkylbenzene sulfonate (LAS) in sewage sludge used on agricultural soil.

Deterministic and probabilistic risk assessments were developed for commercial LAS in agricultural soil amended with sewage sludge. The procedure done according to ILSI Europe's Conceptual Framework [Schowanek, D., Carr, R., David, H., Douben, P., Hall, J., Kirchmann, H., Patria, L., Sequi, P., Smith, S., Webb, S.F., 2004. A risk-based methodology for deriving quality standards for organic contaminants in sewage sludge for use in agriculture-conceptual Framework. Regul. Toxicol. Pharmacol. 40 (3), 227-251], consists of three main steps. First, the most sensitive endpoint was determined. This was found to be the chronic ecotoxicity of LAS to soil invertebrates and plants. Additional endpoints, such as potential for plant uptake and transfer in the food chain, leaching to groundwater, surface erosion run-off, human health risk via drinking water, plant consumption and soil ingestion were also systematically evaluated but were all assessed to be of little toxicological significance. In the second step, a back-calculation was conducted from the Predicted No-Effect Concentration in soil (PNECsoil) to a safe level of LAS in sludge (here called 'Sludge Quality Standard'; SQS). The deterministic approach followed the default agricultural soil exposure scenario in the EU-Technical Guidance Document (TGD). The SQS for LAS was calculated as 49 g/kg sludge Dry Matter (DM). In order to assess the potential variability as a result of varying agricultural practices and local environmental conditions, two probabilistic exposure assessment scenarios were also developed. The mean SQS was estimated at 55 and 27.5 g/kg DM for the homogeneous soil mixing and soil injection scenarios, respectively. In the final step, the resulting SQS values were evaluated for consistency and relevance versus available information from agricultural experience and field tests. No build-up, adverse impact on soil fertility, agronomic performance, or animal/human health have been reported for agricultural fields which have received sludge with high LAS levels for up to 30 years. Distribution statistics of LAS concentrations in anaerobically digested sewage sludge measured across Europe were created (mean value: 5.56 g LAS/kg sludge DM). When compared to the above mean SQS values, adequate risk characterisation ratios of 0.08-0.2 were found. The 'ecological risk' parameter calculated for anaerobic sludge from the probabilistic approaches was below 3%. A regulatory Limit Value for LAS of 2.60 g/kg sludge DM was originally proposed in the 3rd Draft of the Working Document on Sludge [CEC, 2000b. Working Document on Sludge. Third Draft, Brussels 27 April 2000, DG. Environment, 18 p.]. The current assessment, based on an updated dataset and a refined assessment procedure, suggests that the need for a limit value for LAS in sewage sludge cannot be substantiated on a risk basis.

Construction and evaluation of a transgenic hsp16-GFP-lacZ Caenorhabditis elegans strain for environmental monitoring.

A novel integrated transgenic Caenorhabditis elegans strain (PC161) incorporates a double reporter construct with green fluorescent protein (GFP) and lacZ genes fused in-frame into the second exon of the hsp16-1 gene. This construct also includes the Simian Virus 40 (SV40) nuclear localization signal such that the fusion protein accumulates in the nuclei of expressing cells. The PC161 strain was used to monitor the effects of several known stressors, including heat, cadmium, and microwave radiation. The time course of induction was similar for both reporters but was strongly influenced by pretreatment conditions. The PC161 worms kept at 15 degrees C beforehand showed a steady increase in reporter expression (up to at least 16 h) when heated to 30 degrees C. However, if washed on ice prior to heat stress at 30 degrees C, PC161 worms showed a much steeper rise in reporter expression, reaching a maximum after 2.5 h and then plateauing. Heat shock induced strong expression of both reporter genes in all tissues apart from the germ line and early embryos. A highly significant linear dose-response relationship was observed for both transgenes with increasing cadmium concentrations (5-100 microg/ml). Prolonged exposure to microwave radiation (750 MHz and 0.5 W for 16 h) also induced expression of both transgenes at 25 and (to some extent) 27 degrees C, but only beta-galactosidase activity was detectable at 23 degrees C, and neither reporter was detectably expressed at 21 degrees C. Throughout all exposures, the lacZ reporter product was more readily detectable than coexpressed GFP. However, the GFP reporter affords opportunities to monitor the stress response in living worms.