Towards realistic ecotoxicity evaluation of nanoparticles
Nanotechnology, the science of all things very small, has changed products and processes in fields from consumer electronics to energy to cosmetics. However, the very properties that make nanomaterials so unique and exciting in engineered devices – largely related to their chemical reactivity and electrical and magnetic effects – could induce ecotoxicity in the sensitive microbial ecosystems found in water and soil. Scientists addressed the need for a more realistic hazard and risk assessment of exposure to engineered NPs with EU support of the project MICRONANOTOX (Microbial community nano-ecotoxicology: interplay between effects on structure and the consequent effects on function). They chose two of the most important commercial engineered NPs, silver and zinc oxide, and investigated effects at environmentally relevant concentrations. Attention was also given to how the engineered NPs are influenced by their respective environments through interactions that may modify their structures or properties. The research highlighted the difficulty of measuring and analysing long-term NP-specific effects on microbial populations in aqueous environments due to insufficient sensitivity of common analytical techniques. Measurement in soil was complicated by the high background of naturally occurring particles. The team was able to observe interactions between the microbial communities and the engineered NPs. For example, the microbes exuded substances leading to formation of so called eco-coronas of natural organic macromolecules around the NPs. Scientists also applied the well-established, cultivation-independent community fingerprinting method called terminal restriction fragment length polymorphism. They found that the biodiversity measure in both terrestrial and aquatic microbial communities was not well suited to detection of NP-induced stress at low NP concentrations. Time effects were more important than stress ones, making it difficult to distinguish between stress-related NP effects and time-related non-NP effects during long-term exposures. This project has contributed to the need for environmentally more realistic hazard and risk assessment of NPs for microbial communities in large part by revealing the path for future research. In addition to technical difficulties with current analytical methods, future research must take into account interactions between the metal NPs and the microbes as they can strongly influence the properties of the NPs themselves.
Keywords
Ecotoxicity, nanoparticles, nanotechnology, microbial, ecosystems
