Ecotoxicity test methods for engineered nanomaterials: Practical experiences and recommendations from the bench

Abstract

Abstract-Ecotoxicology research is using many methods for engineered nanomaterials (ENMs), but the collective experience from researchers has not been documented. This paper reports the practical issues for working with ENMs and suggests nano-specific modifications to protocols. The review considers generic practical issues, as well as specific issues for aquatic tests, marine grazers, soil organisms, and bioaccumulation studies. Current procedures for cleaning glassware are adequate, but electrodes are problematic. The maintenance of exposure concentration is challenging, but can be achieved with some ENMs. The need to characterize the media during experiments is identified, but rapid analytical methods are not available to do this. The use of sonication and natural/synthetic dispersants are discussed. Nano-specific biological endpoints may be developed for a tiered monitoring scheme to diagnose ENM exposure or effect. A case study of the algal growth test highlights many small deviations in current regulatory test protocols that are allowed (shaking, lighting, mixing methods), but these should be standardized for ENMs. Invertebrate (Daphnia) tests should account for mechanical toxicity of ENMs. Fish tests should consider semistatic exposure to minimize wastewater and animal husbandry. The inclusion of a benthic test is recommended for the base set of ecotoxicity tests with ENMs. The sensitivity of soil tests needs to be increased for ENMs and shortened for logistics reasons; improvements include using Caenorhabditis elegans, aquatic media, and metabolism endpoints in the plant growth tests. The existing bioaccumulation tests are conceptually flawed and require considerable modification, or a new test, to work for ENMs. Overall, most methodologies need some amendments, and recommendations are made to assist researchers. Environ. Toxicol. Chem. 2012;31:15-31. # 2011 SETAC

Potential scenarios for nanomaterial release and subsequent alteration in the environment

“…The analytical methods to identify and especially to characterize and quantify ENM at micrograms per liter or lower concentrations in natural systems are not yet available, with the possible exception of fullerenes [87,88]. However, characterizing PW-ENM coming out of products could be addressed by using existing techniques, as described in the accompanying review on analysis of ENM [89]. Many efforts are underway to apply these techniques to ENM in environmental and biological media [90].…”

“…In addition, effects tests that are conducted in artificial media, such as algal growth media, might not accurately reflect the exposure scenarios that will be observed in the natural environment (see Handy et al [89] in this issue).…”

Metal‐based nanoparticles in soil: Fate, behavior, and effects on soil invertebrates

“…Therefore, some attention should be given to this issue when designing experiments and choosing the spiking procedures. Although the review by Handy et al [72] on practical experiences and recommendations does mention soil, only little attention has been given to soil experiments. However, prior studies with NPs in soils have presented different contamination methodologies, including mixing the NPs powder directly in with the soil, adding a stock dispersion made in distilled water to soil [54], or preparing a stock dispersion in soil elutriate that is then mixed in with the soil [59].…”

Paradigms to assess the environmental impact of manufactured nanomaterials

“…Their work provided the impetus for this article, and the results are contained in this issue's three critical reviews authored by Handy et al [14], von der Kammer et al [15], and Nowack et al [18].…”

“…Complex environments, whether natural or laboratory assays, bring specific challenges. These challenges include the fact that natural environments are not at equilibrium; the redox potential of a natural environment is difficult to mimic in a laboratory bioassay; and nanomaterial aggregation state changes continuously during bioassays [14]. Differentiating engineered nanomaterials from backgrounds of similar but natural materials is also difficult.…”