A weight of evidence approach for hazard screening of engineered nanomaterials.

Hazard identification is an important step in assessing nanomaterial risk and is required under multiple regulatory frameworks in the US, Europe and worldwide. Given the emerging nature of the field and complexity of nanomaterials, multiple studies on even basic material properties often result in varying data pointing in different directions when data interpretation is attempted. Weight of evidence (WOE) evaluation has been recommended for nanomaterial risk assessment, but the majority of WOE frameworks are qualitative in nature and do not satisfy the growing needs for objectivity and transparency that are necessary for regulatory decision making. This paper implements a quantitative WOE framework that utilizes multi-criteria decision analysis methodology for integrating individual studies on nanomaterial hazard resulting from physico-chemical and toxicological properties of nanomaterials. For the first time, a WOE approach explicitly integrates expert evaluation of data quality of available information. Application of the framework is illustrated for titanium dioxide nanoparticles (nano-TiO2), but the approach is designed to compare the relative hazard of several nanomaterials as well as emerging stressors in general.

Application of a quantitative weight of evidence approach for ranking and prioritising occupational exposure scenarios for titanium dioxide and carbon nanomaterials.

Substantial limitations and uncertainties hinder the exposure assessment of engineered nanomaterials (ENMs). The present deficit of reliable measurements and models will inevitably lead in the near term to qualitative and uncertain exposure estimations, which may fail to support adequate risk assessment and management. Therefore it is necessary to complement the current toolset with user-friendly methods for near-term nanosafety evaluation. This paper proposes an approach for relative exposure screening of ENMs. For the first time, an exposure model explicitly implements quantitative weight of evidence (WoE) methods and utilises expert judgement for filling data gaps in the available evidence-base. Application of the framework is illustrated for screening of exposure scenarios for nanoscale titanium dioxide, carbon nanotubes and fullerenes, but it is applicable to other nanomaterials as well. The results show that the WoE-based model overestimates exposure for scenarios where expert judgement was substantially used to fill data gaps, which suggests its conservative nature. In order to test how variations in input data influence the obtained results, probabilistic Monte Carlo sensitivity analysis was applied to demonstrate that the model performs in stable manner.

Risk assessment of engineered nanomaterials: a review of available data and approaches from a regulatory perspective.

It has been largely recognised that substantial limitations and uncertainties make the conventional risk assessment (RA) of chemicals unfeasible to apply to engineered nanomaterials (ENMs) today, which leaves the regulators with little support in the near term. The aim of this paper is to discuss the state of the art in the area of the RA of nanomaterials, focusing on the available data and approaches. There is a paucity of reliable information in the online safety databases and the literature is dominated by (eco)toxicity studies, while the nano-exposure research lags behind. Most of the reviewed nano-RA approaches are designed to serve as preliminary risk screening and/or research prioritisation tools and are not intended to support regulatory decision making. In this context, we recommend to further study the possibilities to apply complementary/alternative tools for near-term RA of ENMs in order to facilitate their timely regulation, using the data that are currently available in the literature.