Comparison of species sensitivity distribution modeling approaches for environmental risk assessment of nanomaterials – a case study for silver and titanium dioxide representative materials

Sørensen, Sara Nørgaard; Wigger, Henning; Zabeo, Alex; Semenzin, Elena; Hristozov, Danail; Nowack, Bernd; Spurgeon, David J. ORCID: https://orcid.org/0000-0003-3264-8760; Baun, Anders. 2020 Comparison of species sensitivity distribution modeling approaches for environmental risk assessment of nanomaterials – a case study for silver and titanium dioxide representative materials. Aquatic Toxicology, 225, 105543. 8, pp. https://doi.org/10.1016/j.aquatox.2020.105543

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Abstract/Summary

Species sensitivity distributions (SSDs) are used in chemical safety assessments to derive predicted-no-effect-concentrations (PNECs) for substances with a sufficient amount of relevant and reliable ecotoxicity data available. For engineered nanomaterials (ENMs), ecotoxicity data are often compromised by poor reproducibility and the lack of nano-specific characterization needed describe an ENM under test exposure conditions. This may influence the outcome of SSD modelling and hence the regulatory decision-making. This study investigates how the outcome of SSD modelling is influenced by: 1) Selecting input data based on the nano-specific “nanoCRED” reliability criteria, 2) Direct SSD modelling avoiding extrapolation of data by including long-term/chronic NOECs only, and 3) Weighting data according to their nano-specific quality, the number of data available for each species, and the trophic level abundance in the ecosystem. Endpoints from freshwater ecotoxicity studies were collected for the representative nanomaterials NM-300 K (silver) and NM-105 (titanium dioxide), evaluated for regulatory reliability and scored according to the level of nano-specific characterization conducted. The compiled datasets are unique in exclusively dealing with representative ENMs showing minimal batch-to-batch variation. The majority of studies were evaluated as regulatory reliable, while the degree of nano-specific characterization varied greatly. The datasets for NM-300 K and NM-105 were used as input to the nano-weighted n-SSWD model, the probabilistic PSSD+, and the conventional SSD Generator by the US EPA. The conventional SSD generally yielded the most conservative, but least precise HC5 values, with 95 % confidence intervals up to 100-fold wider than the other models. The inclusion of regulatory reliable data only, had little effect on the HC5 generated by the conventional SSD and the PSSD+, whereas the n-SSWD estimated different HC5 values based on data segregated according to reliability, especially for NM-105. The n-SSWD weighting of data significantly affected the estimated HC5 values, however in different ways for the sub-datasets of NM-300 K and NM-105. For NM-300 K, the inclusion of NOECs only in the weighted n-SSWD yielded the most conservative HC5 of all datasets and models (a HC5 based on NOECs only could not be estimated for NM-105, due to limited number of data). Overall, the estimated HC5 values of all models are within a relatively limited concentration range of 25−100 ng Ag/L for NM-300 K and 1−15 μgTiO2/L for NM-105.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1016/j.aquatox.2020.105543
UKCEH and CEH Sections/Science Areas:	Pollution (Science Area 2017-)
ISSN:	0166-445X
Additional Keywords:	nanoecotoxicology, regulatory reliability, data weighting, risk assessment, PNEC
NORA Subject Terms:	Ecology and Environment Biology and Microbiology
Date made live:	05 Jul 2020 21:20 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/528089

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