Modeling Approaches for Characterizing and Evaluating Environmental Exposure to Engineered Nanomaterials in Support of Risk-Based Decision Making

Abstract

As the use of engineered nanomaterials becomes more prevalent, the likelihood of unintended exposure to these materials also increases. Given the current scarcity of experimental data regarding fate, transport, and bioavailability, determining potential environmental exposure to these materials requires an in depth analysis of modeling techniques that can be used in both the near- and long-term. Here, we provide a critical review of traditional and emerging exposure modeling approaches to highlight the challenges that scientists and decision-makers face when developing environmental exposure and risk assessments for nanomaterials. We find that accounting for nanospecific properties, overcoming data gaps, realizing model limitations, and handling uncertainty are key to developing informative and reliable environmental exposure and risk assessments for engineered nanomaterials. We find methods suited to recognizing and addressing significant uncertainty to be most appropriate for near-term environmental exposure modeling, given the current state of information and the current insufficiency of established deterministic models to address environmental exposure to engineered nanomaterials.

Development and application of the adverse outcome pathway framework for understanding and predicting chronic toxicity: I. Challenges and research needs in ecotoxicology

“…For example, the influence of external exposure conditions can be modeled using chemical fate and speciation models (Mackay and Webster, 2003;Fu et al, 2009;Rendal et al, 2011;Arnot et al, 2012;Hendren et al, 2013). A wide variety of chemical structure-based in silico prediction models are available that allow evaluating certain ADME characteristics (Kulkarni et al, 2005;Gleeson, 2008;Yang et al, 2012;Piechota et al, 2013) or a chemical's ability to interact with a particular MIE-associated target (Ellison et al, 2011;Enoch and Cronin, 2012;Rana et al, 2012;Vedani et al, 2012;Vinken, 2013;Wu et al, 2013).…”

A Review of the Properties and Processes Determining the Fate of Engineered Nanomaterials in the Aquatic Environment

“…A key challenge in respect to NMs is that environmental fate models developed for traditional classes of micropollutants are not applicable to NMs as such, and need consideration of a number of particle-related adjustments so that they describe the relevant processes that govern their environmental fate (Scheringer, 2008). Modeling approaches have recently been used on these lines to estimate the potential environmental exposure to different NMs from manufacture, use, and disposal of materials and products of nanotechnologies (Hendren, 2013). The value derived from such modeling is the predicted environmental concentration (PEC).…”

Emerging patterns for engineered nanomaterials in the environment: a review of fate and toxicity studies

“…There are still major strategic knowledge gaps for even the most widely used nanoparticles (NPs) involving their postproduction life cycles, including entry into the environment, environmental pathways, eventual environmental fate, and potential ecotoxicological effects. Actual environmental concentrations of engineered nanomaterials (ENMs) are largely unknown (PeraltaVidea et al 2011), though recent release estimates have been completed (Gottschalk et al 2009;Hendren et al 2013;Tovar-Sánchez et al 2013) and there is emerging evidence that manufactured NPs (\100 nm), including TiO 2 , are present in wastewater (Kiser et al 2009;Westerhoff et al 2011) and waste leachate (Hennebert et al 2013).…”