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Open AccessArticle

Evaluation of Existing Models to Estimate Sorption Coefficients for Ionisable Pharmaceuticals in Soils and Sludge

Department of Environment and Geography, University of York, York YO10 5NG, UK
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Author to whom correspondence should be addressed.
Current Affiliation and Address: School of Geography, Faculty of Environment, University of Leeds, Leeds LS2 9JT, UK.
Toxics 2020, 8(1), 13; https://doi.org/10.3390/toxics8010013
Received: 17 January 2020 / Revised: 7 February 2020 / Accepted: 8 February 2020 / Published: 11 February 2020
(This article belongs to the Section Risk Assessment and Risk Management)
In order to assess the environmental risk of a pharmaceutical, information is needed on the sorption of the compound to solids. Here we use a high-quality database of measured sorption coefficients, all determined following internationally recognised protocols, to evaluate models that have been proposed for estimating sorption of pharmaceuticals from chemical structure, some of which are already being used for environmental risk assessment and prioritization purposes. Our analyses demonstrate that octanol-water partition coefficient (Kow) alone is not an effective predictor of ionisable pharmaceutical sorption in soils. Polyparameter models based on pharmaceutical characteristics in combination with key soil properties, such as cation exchange capacity, increase model complexity but yield an improvement in the predictive capability of soil sorption models. Nevertheless, as the models included in this analysis were only able to predict a maximum of 71% and 67% of the sorption coefficients for the compounds to within one log unit of the corresponding measured value in soils and sludge, respectively, there is a need for new models to be developed to better predict the sorption of ionisable pharmaceuticals in soil and sludge systems. The variation in sorption coefficients, even for a single pharmaceutical across different solid types, makes this an inherently difficult task, and therefore requires a broad understanding of both chemical and sorbent properties driving the sorption process. View Full-Text
Keywords: hydrophobic partitioning; acid; base; uncharged; fate hydrophobic partitioning; acid; base; uncharged; fate
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Carter, L.J.; Wilkinson, J.L.; Boxall, A.B.A. Evaluation of Existing Models to Estimate Sorption Coefficients for Ionisable Pharmaceuticals in Soils and Sludge. Toxics 2020, 8, 13.

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