Extracts of passive samplers deployed in variably contaminated wetlands in the Athabasca oil sands region elicit biochemical and transcriptomic effects in avian hepatocytes.

Abstract

Recent contaminant monitoring in boreal wetlands situated in Alberta s Athabasca oil sands region revealed increased concentrations of polycyclic aromatic compounds (PACs) in passive sampling devices deployed in wetlands close to bitumen surface mining operations. In this study, graded concentrations of semipermeable membrane device (SPMD) extracts, collected from 4 wetlands with variable burdens of PACs, were administered to chicken and double-crested cormorant (DCCO) embryonic hepatocytes to determine effects on 7-ethoxyresorufin-O-deethylase (EROD) activity and mRNA expression. Concentrations and composition of PACs detected in SPMDs varied among sites, and the proportion of alkyl PACs was greater than parent compounds at all sites. ∑PACs was highest in SPMDs deployed within 10 km of mining activity (near-site wetland [5930 ng SPMD-1]) compared to those ~50 km south (far-site wetland [689 ng SPMD-1]). Measures of EROD activity and Cyp1a4 mRNA expression allowed the ranking of wetland sites based on aryl hydrocarbon receptor-mediated endpoints; EROD activity and Cyp1a4 mRNA induction was highest at the near-site wetland). ToxChip PCR arrays (one chicken and one DCCO) provided an exhaustive transcriptomic evaluation across multiple toxicological pathways upon exposure to the SPMD extracts. Study sites with the greatest PAC concentrations had the most genes altered on the chicken ToxChip (12-15/43 genes). Exposure of avian hepatocytes to SPMD extracts from variably contaminated wetlands highlighted traditional PAC-related toxicity pathways as well as other novel mechanisms of action. A novel combination of passive sampling techniques and high-throughput toxicity evaluation techniques shows promise in terms of identifying hotspots of chemical concern in the natural environment.