Citation:

Stevens, C., J. Patel, M. Koopmans, J. Olmstead, S. Hilal, N. Pope, E. Weber, AND K. Wolfe. Demonstration of a consensus approach for the calculation of physicochemical properties required for environmental fate assessments. CHEMOSPHERE. Elsevier Science Ltd, New York, NY, 194:94-106, (2018). https://doi.org/10.1016/j.chemosphere.2017.11.137

Impact/Purpose:

Environmental fate and transport models can be used to assess the likelihood of environmental exposure of vulnerable organisms to toxic organic chemicals dissolved in groundwater, surface water, and runoff. These models generally require the user to provide input parameters that characterize the effects of partitioning as well as abiotic and microbial transformation reactions on the fate of a chemical. Model input parameters may include physicochemical properties (e.g., water solubility), partition coefficients (e.g., sediment-water partition coefficients) and transformation rate constants. A primary objective of this paper is to demonstrate the value of using consensus predictions from a variety of different physicochemical property calculators that take different approaches to calculating specific physicochemical properties. The results of this comparison of calculator performance demonstrate the value of applying a variety of calculators that use different estimation algorithms to estimate the physicochemical property values for a chemical of interest. For a list of structurally related chemicals, a comparison of calculator performance against available measured property values can be used to select the calculator with the best performance for a particular property.

Description:

Eight software applications are compared for their performance in estimating the octanol-water partition coefficient (Kow), melting point, vapor pressure and water solubility for a dataset of polychlorinated biphenyls, polybrominated diphenyl ethers, polychlorinated dibenzodioxins, and polycyclic aromatic hydrocarbons. The predicted property values are compared against a curated dataset of measured property values compiled from the scientific literature with careful consideration given to the analytical methods used for property measurements of these hydrophobic chemicals. The variability in the predicted values from different calculators generally increases for higher values of Kow and melting point and for lower values of water solubility and vapor pressure. For each property, no individual calculator outperforms the others for all four of the chemical classes included in the analysis. Because calculator performance varies based on chemical class and property value, the geometric mean and the median of the calculated values from multiple calculators that use different estimation algorithms are recommended as more reliable estimates of the property value than the value from any single calculator.

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