PETROTOX: An aquatic toxicity model for petroleum substances

Abstract

A spreadsheet model (PETROTOX) is described that predicts the aquatic toxicity of complex petroleum substances from petroleum substance composition. Substance composition is characterized by specifying mass fractions in constituent hydrocarbon blocks (HBs) based on available analytical information. The HBs are defined by their mass fractions within a defined carbon number range or boiling point interval. Physicochemical properties of the HBs are approximated by assigning representative hydrocarbons from a database of individual hydrocarbons with associated physicochemical properties. A three-phase fate model is used to simulate the distribution of each structure among the water-, air-, and oil-phase liquid in the laboratory test system. Toxicity is then computed based on the predicted aqueous concentrations and aquatic toxicity of each structure and the target lipid model. The toxicity of the complex substance is computed assuming additivity of the contribution of the individual assigned hydrocarbons. Model performance was evaluated by using direct comparisons with measured toxicity data for petroleum substances with sufficient analytical characterization to run the model. Indirect evaluations were made by comparing predicted toxicity distributions using analytical data on petroleum substances from different product categories with independent, empirical distributions of toxicity data available for the same categories. Predictions compared favorably with measured aquatic toxicity data across different petroleum substance categories. These findings demonstrate the utility of PETROTOX for assessing environmental hazards of petroleum substances given knowledge of substance composition.

A re‐evaluation of PETROTOX for predicting acute and chronic toxicity of petroleum substances

“…This nonlinear partitioning behavior may reflect the impact of low solubility and slow toxicokinetics [47] or other competing processes that limit accumulation in the target lipid for these low-solubility constituents. The WAF exposure model and TLM have been validated previously [9,11,37,48,49] and shown to provide similar errorbased analysis of residual model errors. The WAF exposure model and TLM have been validated previously [9,11,37,48,49] and shown to provide similar errorbased analysis of residual model errors.…”

“…This block is then simulated using the physicochemical properties from a library of individual representative structures that map to this block [9]. As an example, the C12 di-aromatic block (e.g., C2-naphthalenes) represents a single block.…”

“…However, an important modification was implemented [9] to account for the reduced bioavailability of hydrophobic constituents. However, an important modification was implemented [9] to account for the reduced bioavailability of hydrophobic constituents.…”

“…The hydrocarbon block method was implemented in the PETROTOX [9] and PETRORISK [8] models to conduct hazard and risk assessments, respectively (the latter under the Registration, Evaluation, Authorization, and Restriction of Chemicals [REACH] of the European Commission). The blocks need to be sufficiently narrow so that the actual constituents within these blocks can be reasonably approximated by representative physicochemical properties.…”

Physical and Chemical Characterization of Crude Oil-Water Mixtures: Understanding the Effects of Interfacial Process to Chemical Bioavailability

“…Predictive models accounting for the wide range of toxicity of petroleum hydrocarbons based on the narcosis target lipid model (NTLM) have been developed and validated (Di Toro and McGrath, 2000;French-McCay, 2002;McGrath and Di Toro, 2009;Redman et al, 2012b). The NTLM predicts the toxicity of a group of compounds that exert the same toxic mode of action (narcosis) and uses the inverse relationship observed between the lethal concentration to 50 % of the organisms (LC50) and the octanol-water portioning coefficient (Kow) (McGrath et al, 2005).…”