Assessment of Applicability of Existing Approaches of Predicting Bioaccumulation of Conventional Substances to Nanomaterials

As the experimental determination of bioaccumulation is challenging, a number of approaches have been developed for its prediction. Since nanomaterials (NMs) have been shown to bioaccumulate, it is imperative to assess the applicability of these predictive approaches to NMs. KOW may not be applicable for some NMs that are not found in either the octanol or water phases but rather are found at the interface. Subsequently, the Kow s of some NMs obtained are shown not to correlate well with the experimentally determined bioaccumulation. The implementation of the quantitative structure activity relationships (QSARs) to NMs is also challenging because the bioaccumulation of NMs depends on nano-specific properties such as shape, size, and surface area. Subsequently, there is a need to develop new QSAR models based on these new nano-descriptors where current efforts appear to focus on nanodescriptors based on digital processing of NM images as well as the conversion of surface chemistry parameters into adsorption indices. Water solubility can be used as a screening tool for the exclusion of NMs with short half-times for further investigation for bioaccumulation studies. while adaptation of fugacity/aquivalence models, which include physicochemical properties of NMs, may give some insights on the bioaccumulation potential of NMs, especially with the addition of a ‘biota’ component. The use of kinetic models, including physiologically based pharmacokinetic (PBPK) models, appears to be the most suitable approach for predicting bioaccumulation of NMs. Furthermore, as bioaccumulation of NMs depends on a number of biotic and abiotic factors, it is important to take these factors into account when modelling bioaccumulation and interpreting bioaccumulation results.

Authors: Utembe W, Wepener V, Yu IJ, Gulumian M. ; Full Source: Environmental Toxicology & Chemistry. 2018 Aug 17. doi: 10.1002/etc.4253. [Epub ahead of print]