Ecotoxicity test methods and environmental hazard assessment for engineered nanoparticles

Abstract

This paper considers whether current standard ecotoxicity methods are fit for purpose for assessing the hazards of engineered nanoparticles. We conclude that the types of test species and biological endpoints used within standard environmental hazard assessment frameworks are generally appropriate. However, there are areas of considerable uncertainty associated with characterisation of nanoparticle exposure in test systems that apply to all ecotoxicity testing guidelines, except those in which dosing of nanoparticles is oral. These include the way in which the substance is dosed into, and maintained within, the test medium; measurement and characterisation of nanoparticles in the test system; better understanding and reporting of abiotic factors that influence behaviour of nanoparticles in the test medium; and agreement on how dosimetric data should be reported.

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

“…These generic issues can present practical problems, such as how to clean and prepare test vessels, but they also can represent issues of fundamental scientific importance, such as experimental design and the use of controls. The scientific issue around experimental design, including the use of reference ENMs, particle size controls, whether to use dispersing agents, and so forth, have been discussed extensively [5,11,12]. The present study focuses on the practical aspects of deciding what to do and how to do it.…”

“…Clearly, imposing the concepts and validation criterion used in regulatory methods on the scientific community for ENMs generally is not desirable. Some commonly agreed-upon aspects will emerge, such as the use of suitable controls [5], but at this early stage, the opportunity exists to incorporate environmentally relevant conceptual models for ENM in the testing strategy [24].…”

“…The minimum characterization requirements for stock solutions of ENMs have been discussed at length, with agreement that stock solutions can be verified [5,11], but less consideration has been given to practical measurement during an ecotoxicity test. A consensus view from the scientific community on what dose metric should be used routinely in ecotoxicity testing is still forming, and collecting a sufficient weight of evidence for or against using a particular dose metric (such as particle size, particle number, or mass concentration) in a regulatory test will take some years, and it may be specific for some types of ENMs.…”

“…These standardized tests have aspects of international harmonization (the Organisation for Economic Co-operation and Development [OECD] tests, [5]; International Organization for Standardization, Daphnia immobilization test [6]), and many countries and institutions also have their own protocols. For example, the American Society of Testing and Materials Committee on Biological Effects and Environmental Fate has written protocols for testing substances on a range of aquatic invertebrates and fish [7].…”

“…Consequently, some debate has ensued about the utility of existing regulatory tests for ENMS. The consensus is that the existing methods and framework for hazard assessment (standard test organisms, mortality, growth and reproduction endpoints) are generally fit for this purpose, but the details within each group of tests may require modification or optimization to work well with ENMs [5]. Recently, the OECD made some preliminary recommendations on how to dose toxicity test systems with ENMs [9], and the long process of validating standard regulatory tests for new ENMs has begun (the OECD sponsorship program, [10]).…”