ENM fate in freshwater through adaption of USEtox

Engineered nanomaterials (ENMs) have in recent time received substantial attention, both in scientific and consumer circles, as these materials are introduced to a steadily increasing number of consumer products. This has led to environmental concerns on how this new material class behaves in the environment, at which concentrations organisms are exposed to the materials and what effects these materials may have on the environment. In relation to metal-oxide engineered nanomaterials (ENMs), as is the general case for ENMs, many environmental aspects are still unknown and/or hence not properly scientifically mapped. One approach that has not been given much attention in relation to environmental assessment of ENM, more precisely the fate, exposure and effect modelling of metal-oxide ENMs is the application of adapted characterization modelling (ACM) and hence application of characterisation models designed for single (chemical) compound assessment e.g. the USEtoxTM model for characterisation of ENM effect potentials.
The purpose of this study is therefore to evaluate if existing characterisation model such as the USEtoxTM model can be applied for characterisation modelling of ENMs applying the principles of ACM. The primarily principle of adapted characterisation modelling relies on the recognition of the fact that nano-materials do not behave like single chemical compounds in the environment. The second principle of ACM relies on the fact that existing chemical characterisation can be applied to model hypothetical representatives for effect causing emissions such as groups of chemicals (i.e. equivalence approaches applied to model mercury by). In this study the approach taken was therefore to consider if USEtoxTM characterisation of ENMs is possible and appropriately valid. The characterisation was done by relating nano-material properties to chemical properties and hence model the nano-material as a chemical with representative fate and exposure patterns.
In the case study in-volatile ENM’s (metal-oxides) were characterised in USEtoxTM applying adapted characterisation modelling. The result obtained indicates that with some limitations the approach is considered valid – the characterisation factors are considered uncertain relating to several facts such as lack of environmental studies on ENMs making is hard to assess the general environmental behaviour of ENMs and hence relate this environmental behaviour to similar “chemical behaviour”.