Fate and Toxicity of CuO Nanospheres and Nanorods used in Al/CuO Nanothermites Before and After Combustion

Abstract

Although nanotechnology advancements should be fostered, the environmental health and safety (EHS) of nanoparticles used in technologies must be quantified simultaneously. However, most EHS studies assess the potential implications of the free nanoparticles which may not be directly applicable to the EHS of particles incorporated into in-use technologies. This investigation assessed the aquatic toxicological implications of copper oxide (CuO) nanospheres relative to CuO nanorods used in nanoenergetic applications to improve combustion. Particles were tested in both the as-received form and following combustion of a CuO/aluminum nanothermite. Results indicated nanospheres were more stable in water and slowly released ions, while higher surface area nanorods initially released more ions and were more toxic but generally less stable. After combustion, particles sintered into larger, micrometer-scale aggregates, which may lower toxicity potential to pelagic organisms due to deposition from water to sediment and reduced bioavailability after complexation with sediment organic matter. Whereas the larger nanothermite residues settled rapidly, implying lower persistence in water, their potential to release dissolved Cu was higher which led to greater toxicity to Ceriodaphnia dubia relative to parent CuO material (nanosphere or rod). This study illustrates the importance of considering the fate and toxicology of nanoparticles in context with their relevant in-use applications.

Gaining a Critical Mass: A Dose Metric Conversion Case Study Using Silver Nanoparticles

“…Previous research reported substantially different dissolution kinetics between citrate- and PVP-AgNPs. , Further, research suggested that the applicability of a TESA dose metric is confounded for by ligands, such as natural organic matter . However, in pristine media it generally appears that TESA is a better predictor of acute toxicity for soluble NPs, as shown for differently shaped microsized , and nanosized CuO particle suspensions. Surface area has also shown efficacy for CeO NPs .…”

“…Reviews − and documents on the toxicology of nanoparticles (NPs) have discussed the applicability of the mass-only metric without consensus. Aerosol toxicologists have recognized the need for alternative dose metrics (particle count, surface area, charge, shape) to express the implications of NPs. − Most aquatic ecotoxicology studies continue to express NP toxicity primarily by mass, with recent exceptions. − This is due in part to the intensiveness of characterizing all needed NP attributes (size, surface area, number, agglomeration, dissolution) in aquatic exposures, changes during the assay, lack of standardized guidance on how to apply alternative dose metrics, and analytical limitations (low μg/L) at environmentally and toxicologically relevant concentrations . However, the large variability in ecotoxicological end points for the same type of NP provides evidence that total NP mass is not predictive of biological effects.…”

Nanostructured Energetic Composites: Synthesis, Ignition/Combustion Modeling, and Applications

“…Thus, researchers must carefully refer to the material safety data sheet to follow adequate precautions and arrange appropriate disposal. 174,175 The superiorities of nanostructured energetic composites are already revealed in various forms; however, the control that can be exerted on nanocomposites is insufficient until now. Apart from the layered vapor deposition, most of the abovementioned methods can hardly and effectively modulate the delicate structure of nanocomposites.…”

“…Some reactants and reaction products can be hazardous to human beings and the environment, particularly when the particle diameter reaches nanometer range. Thus, researchers must carefully refer to the material safety data sheet to follow adequate precautions and arrange appropriate disposal. , …”

Adapting OECD Aquatic Toxicity Tests for Use with Manufactured Nanomaterials: Key Issues and Consensus Recommendations

“…The aerosol science literature has addressed alternative dose metrics for particles (e.g., see refs − ), and several recent ecotoxicology studies have reported improved dose–response expression by surface area, − , ion release, , or particle number . However, the development of a standardized alternative dose metric for MNs for hazard assessments is encumbered for a number of reasons: (1) it is unlikely that any one alternative dose metric will provide an improvement over mass for all MNs in all test systems; (2) it is more difficult to directly measure surface areas and particle numbers compared with mass concentrations at bioassay-relevant concentrations in bioassay media, although methods are becoming available; (3) unless size distribution data are known or measurable, polydisperse particle suspensions in test media will further complicate the interpretation of exposure relative to effect; and (4) dynamic changes in dispersion stability or consistency (suspended concentration, agglomeration, and dissolution) confound concise interpretation and render dose metric conversions from size and mass less accurate.…”