Key challenges for nanotechnology: Standardization of ecotoxicity testing.

Nanotechnology is expected to contribute to the protection of the environment, but many uncertainties exist regarding the environmental and human implications of manufactured nanomaterials (MNMs). Contradictory results have been reported for their ecotoxicity to aquatic organisms, which constitute one of the most important pathways for their entrance and transfer throughout the food web. The present review is focused on the international strategies that are laying the foundations of the ecotoxicological assessment of MNMs. Specific advice is provided on the preparation of MNM dispersions in the culture media of the organisms, which is considered a key factor to overcome the limitations in the standardization of the test methodologies.

Towards the standardization of nanoecotoxicity testing: Natural organic matter 'camouflages' the adverse effects of TiO2 and CeO2 nanoparticles on green microalgae.

In the last few years, the emission of CeO2 and TiO2 nanoparticles (NPs) into the environment has been raising concerns about their potential adverse effects on wildlife and human health. Aquatic organisms constitute one of the most important pathways for the entrance of these NPs and transfer throughout the food web, but divergences exist in the experimental data published on their aquatic toxicity. The pressing need for standardization of methods to analyze their ecotoxicity requires aquatic media representing realistic environmental conditions. The present study aimed to determine the usefulness of Suwannee River natural organic matter (SR-NOM) in the assessment of the agglomeration kinetics and ecotoxicity of CeO2 and TiO2 NPs towards green microalgae Pseudokirchneriella subcapitata. SR-NOM alleviated the adverse effects of NPs on algal growth, completely in the case of TiO2 NPs and partially in the case of CeO2 NPs, suggesting a 'camouflage' of toxicity. This behavior has been observed also for other algal species and types of natural organic matter in the literature. Furthermore, SR-NOM markedly increased the stability of the NPs in algal medium, which led to a better reproducibility of the toxicity test results, and provided an electrophoretic mobility similar to that previously reported in various river and groundwaters. Thus, SR-NOM can be a representative sample of what is found in many different ecosystems, and the observed 'camouflage' of the effects of CeO2 and TiO2 NPs on algal cells might be considered as a natural interaction occurring in their standardized ecotoxicological assessment.

Colloidal stability and ecotoxicity of multiwalled carbon nanotubes: Influence of select organic matters.

In the last few years, the release of multiwalled carbon nanotubes (MWCNTs) into the environment has raised serious concerns regarding their fate and potential impacts. Aquatic organisms constitute an important pathway for their entrance and transfer throughout the food web, and the current demand for standardization of methodologies to analyze the interactions of MWCNTs with them requires aquatic media that represent natural systems. However, the inherent hydrophobicity of MWCNTs and the substances present in natural waters may greatly affect their stability and bioavailability. The present study analyzes the influence of the most referenced synthetic and natural organic matters (Sigma-Aldrich humic acid and Suwannee River natural organic matter) in the agglomeration kinetics and ecotoxicity of MWCNTs, with the aim of determining their suitability to fulfill the current standardization requirements. Natural organic matter provides increased colloidal stability to the MWCNTs' dispersions, which results in higher adverse effects on the key invertebrate organism Daphnia magna. Furthermore, the results obtained with this type of organic matter allow for observation of the important role of the outer diameter and content impurities of MWCNTs in their stability and ecotoxicity on daphnids. Sigma-Aldrich humic acid appeared to alter the response of the organisms to carbon nanotubes compared with that observed in the presence of natural organic matter.

Ecotoxicity of multiwalled carbon nanotubes: standardization of the dispersion methods and concentration measurements.

There are currently a variety of applications for multiwalled carbon nanotubes (MWCNTs), but considerable concerns exist regarding their release into the environment. Their potential accumulation by aquatic organisms could lead to transfer throughout food chains. Considering the divergences in experimental data published on the ecotoxicity of carbon nanotubes, further research is required. The dispersion of MWCNTs in aqueous culturing media of organisms as well as the determination of concentrations are relevant aspects to obtain accurate ecotoxicity results. Ultraviolet-visible spectroscopy is one of the most reported techniques to analyze concentration quickly and economically, but the methodologies to prepare dispersions and selecting the wavelengths for ultraviolet-visible measurements have not yet been clearly defined. The present study demonstrates that dispersion procedures influence absorbance, and an approach to determine the most appropriate measurement wavelength is proposed. Ecotoxicity tests with MWCNTs were performed on Vibrio fischeri bacteria, and divergences in the results were observed with respect to those previously reported. The present study contributes to the attempt to overcome the lack of standardization in the environmental assessment of MWCNTs.

Ionic liquids as lubricants or lubrication additives: an ecotoxicity and biodegradability assessment.

This paper reports on the (eco)toxicity and biodegradability of ionic liquids considered for application as lubricants or lubrication additives. Ammonium- and pyrrolidinium-based cations combined with methylsulphate, methylsulphonate and/or (CF(3)SO(2))(2)N(-) anions were investigated in tests to determine their aquatic toxicity using water fleas Daphnia magna, green algae Selenastrum capricornutum and marine bacteria (Vibrio fischeri). Additional test systems with an isolated enzyme (acetylcholinesterase) and isolated leukaemia cells from rats (IPC-81) were used to assess the biological activity of the ionic liquids. These compounds generally exhibit low acute toxicity and biological activity. Their biodegradability was screened according to OECD test procedures 301 B and 301 F. For choline and methoxy-choline ionic liquids ready biodegradability was observed within 5 or 10 d, respectively. Some of the compounds selected have a considerable potential to contribute to the development of more sustainable products and processes.