A comprehensive assessment of the potential environmental implications of engineered nanomaterials (ENMs) requires the development of adequate modeling tools to understand and predict their behavior in different environmental compartments. Multimedia environmental fate models are well-established tools used for decades in the risk assessment of organic pollutants. They are based on a set of essential chemical property data, namely degradation half-lives and equilibrium partition coefficients (e.g. the soil-water distribution coefficient Kd) describing a chemical's relative affinity for different environmental phases.Significant confusion exists in the literature regarding the applicability of equilibrium partition coefficients for ENMs. Despite the lack of a scientific justification, several studies report measured partition coefficients for ENMs or suggest their use predictive tools. However, in contrast to organic chemicals whose environmental fate is largely governed by equilibrium partitioning, the fate of ENMs is exclusively kinetically controlled, because ENMs do not reach thermodynamic equilibrium but are present in the environment as unstable suspensions. In order to clarify existing misconceptions, we here provide a detailed and illustrative analysis of the underlying concepts of equilibrium partitioning and colloid science. We discuss several examples that directly or indirectly prove that equilibrium partition coefficients cannot be determined for ENMs.Appropriate fate descriptors that can be used to describe the interaction of ENMs with natural particles in an environmental fate model are for example attachment efficiencies for aggregation and deposition. We present a new concept for environmental fate models for ENMs, which includes nano-specific fate descriptors representing processes such as aggregation (homo- and heteroaggregation), transformation (e.g. dissolution, surface transformation) and deposition.In the context of risk assessment it is important to recognize the differences between conventional pollutants and ENMs and to adjust existing methods carefully and adequately to account for the ENM specific properties to avoid erroneous predictions of environmental concentrations of ENMs.

What are appropriate fate descriptors and modeling approaches to predict environmental concentrations of engineered nanomaterials for risk assessment?

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.