Considerations of Environmentally Relevant Test Conditions for Improved Evaluation of Ecological Hazards of Engineered Nanomaterials

Abstract

Engineered nanomaterials (ENMs) are increasingly entering the environment with uncertain consequences including potential ecological effects. Various research communities view differently whether ecotoxicological testing of ENMs should be conducted using environmentally relevant concentrations—where observing outcomes is difficult—versus higher ENM doses, where responses are observable. What exposure conditions are typically used in assessing ENM hazards to populations? What conditions are used to test ecosystem-scale hazards? What is known regarding actual ENMs in the environment, via measurements or modeling simulations? How should exposure conditions, ENM transformation, dose, and body burden be used in interpreting biological and computational findings for assessing risks? These questions were addressed in the context of this critical review. As a result, three main recommendations emerged. First, researchers should improve ecotoxicology of ENMs by choosing test endpoints, duration, and study conditions—including ENM test concentrations—that align with realistic exposure scenarios. Second, testing should proceed via tiers with iterative feedback that informs experiments at other levels of biological organization. Finally, environmental realism in ENM hazard assessments should involve greater coordination among ENM quantitative analysts, exposure modelers, and ecotoxicologists, across government, industry, and academia.

Assessing nanomaterial exposures in aquatic ecotoxicological testing: Framework and case studies based on dispersion and dissolution

“…The resulting, more consistently generated data may accelerate the development of ENM databases to foster comparability and predictive tools that might ultimately reduce testing needs. Finally, decisions concerning the extent of efforts to modify test procedures to, for example, produce stable exposures rather than accept exposure variability will likely be subject to regulatory decisions and guidance yet to be resolved (Beaudrie et al 2013a,b;Petersen et al, 2015) but need to be considered in full risk or life cycle assessments (Holden et al, 2016, Godwin et al, 2015. Thus, we caveat that these environmental exposure considerations and regulatory uncertainties are not addressed in the framework and are outside the scope of this hazard data generation focused manuscript.…”

“…We demonstrated hazard testing procedures with focus on critical issues for standardized ecotoxicity testing of ENMs discussed by others (Diamond et al, 2009;Handy et al, 2012;Holden et al, 2016;Hund-Rinke et al, 2015;Klaine et al, 2008;Petersen et al, 2015;Potthoff et al, 2015). Key testing issues derive from the particulate and fibrous nature of ENMs, and their tendency to agglomerate and settle out of suspension in bioassay media, resulting in significant exposure variation and thus complicated dosimetry.…”

“…Interim hazard assessment methods are needed since NEPs are rapidly entering commercial and other markets; investigators need to supply the best available knowledge on ENM toxicological exposure and hazard to facilitate current risk assessment decisions (Godwin et al, 2015;Hansen et al, 2014). A clear and consistent testing framework process for generating hazard data for ENMs is needed, in addition to a more adaptive and diverse set of analyses and techniques for ENM risk assessment (Holden et al, 2016;Hund-Rinke et al, 2015;Jahnel, 2015;Potthoff et al, 2015).…”

“…The need for environmental realism in ENM safety testing is currently being deliberated and is addressed in Tier 5 of the strategy (Collier et al, 2015) and in separate exposure assessments considered in risk decisions (Godwin et al, 2015). Thus, we caveat that additional extensive analysis and consideration is required in risk analysis (Holden et al, 2016).…”

Nanomaterials in the Environment: Perspectives on in Vivo Terrestrial Toxicity Testing

“…Furthermore, abiotic factors can influence specific physicochemical properties of NMs affecting their bioavailability and toxicity (El Badawy et al, 2010;Grillo et al, 2015). Thus, to ensure the reliability and reproducibility of ecotoxicity tests, NMs should be accurately characterized in multiple life cycle endpoints and the experimental parameters should be carefully chosen (Holden et al, 2016).…”