Environmental Hazard Screening of Heterocyclic Polyaromatic Hydrocarbons: Physicochemical Data and In Silico Models

Heterocyclic polyaromatic hydrocarbons (heterocyclic PAHs) are frequently found in the environment yet, compared to homocyclic PAHs, little attention has been paid to their environmental behavior and a comprehensive hazard assessment has not been undertaken. Surprisingly, the physicochemical data necessary to perform at least a screening-level assessment are also limited. To address this, we began by experimentally determining the physicochemical properties of heterocyclic PAHs, namely, water solubility (S_w), n-octanol-water partition coefficients (K_ow), and organic carbon-water partition coefficients (K_oc). The physicochemical data obtained in this study allowed for the development of clear structure-property relationships and evaluation of the predictive power of in silico models including conductor-like screening model for realistic solvation, the poly-parameter linear solvation energy relationship, and the quantitative structure-property relationship. Finally, heterocyclic and homocyclic PAHs were evaluated in terms of persistence, bioaccumulation, mobility, and toxicity to perform a screening-level comparative hazard assessment by integrating the data and evidence from multiple sources.