Superfund Research Program
Predicting the Toxicity of Complex PAH Mixtures
Robyn Tanguay, Ph.D., and her team previously evaluated the developmental toxicity of hundreds of polycyclic aromatic hydrocarbons (PAHs) assessed in the zebrafish model (Geier, 2018 #272). Based on phenotypic responses the team classified these PAHs into eight bins, selected 16 representative PAHs, and conducted RNA sequencing at 48 hour post fertilization to identify gene expression changes as a result of PAH exposure. Using bioinformatics algorithms the team inferred a network that links the PAHs based on coordinated gene responses to PAH exposure. The PAHs formed two broad clusters: Cluster A was transcriptionally more similar to the controls, while Cluster B consisted of PAHs that were generally more developmentally toxic, significantly elevated cyp1a transcript levels. While all cluster B PAHs predominantly activated Ahr2, they also each enriched unique pathways like ion transport signaling, which likely points to differing molecular events between the PAHs downstream of Ahr2. Thus, using a systems biology approach, the team began to evaluate, classify, and define mechanisms of PAH toxicity (Shankar, 2019 #611). Tanguay and her team also collaborated with the Identification of Remediation Technologies and Conditions that Minimize Formation of Hazardous PAH Breakdown Products at Superfund Sites Project to evaluate the toxicological consequenses of steam enhanced extraction (SEE) remediation. Creosote contaminated soil samples collected from the Wyckoff-Eagle Harbor Superfund site were remediated with laboratory scale SEE. The samples were quantified for unsubstituted PAHs and their derivatives and assessed for developmental toxicity. Following SEE, unsubstituted PAH concentrations decreased, while oxygenated PAH concentrations increased in soil and aqueous extracts. Differences in developmental toxicity were linked to the formation of PAH derivatives. SEE is effective in removing unsubstituted PAHs from contaminated soil, but other, potentially more toxic, PAH derivatives are formed (Trine, 2019 #615).