In vitro reproductive-endocrine, and in vivo immunological responses to extracted oil sands-derived naphthenic acids.

摘要

There is concern surrounding the large volumes of oil sands-influenced waters produced by the extraction of oil in the Athabasca region in northern Alberta. These waters contain water soluble organic compounds such as naphthenic acids (NAs) and polycyclic aromatic hydrocarbons (PAHs). The goal of this study was to use in vitro as well as in vivo assays using rainbow trout (Oncorhynchus mykiss) combined with spectroscopic analyses to determine if specific NA fractions obtained from oil sands-influenced waters possess biological activity. NAs were extracted in bulk from oil sands-influenced waters using acid precipitation and then fractionated. NAs fractions were identified and quantified by high resolution mass spectrometry (HRMS), 1H nuclear magnetic resonance (NMR), and attenuated total reflectance (ATR) infrared spectroscopy. The fraction obtained by dichloromethane (DCM) back extraction of base-solubilized showed aromatic compounds around 6.8 -- 8.2 ppm using 1H NMR. This fraction elicited an aryl hydrocarbon receptor (AhR)-mediated activity after 24 h at 5 mg/L. Each fraction contained a carboxylic acid dimer though there were differences in average carbon number and hydrogen deficiency between the samples. The main NA fraction was subsequently used for an in vivo waterborne exposure using rainbow trout. Waterborne exposures were conducted with oil sands-influenced waters, extracted NAs, and benzo[a]pyrene (BaP) as a positive control for 7 d, after which blood, spleen, head kidney, and gill samples were removed to evaluate the distribution of thrombocytes, B-lymphocytes, myeloid cells, and T-lymphocytes. The remaining trout in each experimental tank were injected with inactivated Aeromonas salmonicida and held in laboratory water for 21 d and subjected to similar lymphatic cell evaluation in addition to evaluation of antibody production. Trout in the oil sands-influenced water exposure showed a decrease in B- and T-lymphocytes in blood as well as B-lymphocytes and myeloid cells in spleen and an increase in B-lymphocytes in head kidney. Because Oil sands-influenced waters affected multiple immune parameters, while extracted NAs impacts were limited, the NAs tested here are likely not the cause of immunotoxicity found in the oil sands-influenced water. Taken together, the results of spectroscopic analyses, in vitro assays, and in vivo exposures suggest that compounds capable of activating AhR-mediated pathways are present in oil sands process-affected waters, specifically in the DCM fraction. The identity of the AhR-active and immunotoxic compound(s) remains to be determined.