Aromatic Naphthenic Acids in Oil Sands Process-Affected Water, Resolved by GCxGC-MS, Only Weakly Induce the Gene for Vitellogenin Production in Zebrafish (Danio rerio) Larvae

Abstract

Process waters from oil sands industries (OSPW) have been reported to exhibit estrogenic effects. Although the compounds responsible are unknown, some aromatic naphthenic acids (NA) have been implicated. The present study was designed to investigate whether aromatic NA might cause such effects. Here we demonstrate induction of vitellogenin genes (vtg) in fish, which is a common bioassay used to indicate effects consistent with exposure to exogenous estrogens. Solutions in water of 20-2000 μg L(-1) of an extract of a total OSPW NA concentrate did not induce expression of vtg in larval zebrafish, consistent with earlier studies which showed that much higher NA concentrations of undiluted OSPW were needed. Although 20-2000 μg L(-1) of an esterifiable NA subfraction of the OSPW NA concentrate did induce expression, this was of much lower magnitude to that induced by much lower concentrations of 17α-ethynyl estradiol, indicating that the effect of the total NAs was only weak. However, given the high NA concentrations and large volumes of OSPW extant in Canada, it is important to ascertain which of these esterifiable NA in the OSPW produce the effect. Up to 1000 μg L(-1) of an OSPW subfraction containing only alicyclic NA, and considered by most authors to be NA sensu stricto, did not produce induction; but, as predicted, 10-1000 μg L(-1) of an aromatic NA fraction did. Such effects by the aromatic acids are again consistent with those of only a weak estrogenic substance. These findings may help to focus studies of the most environmentally significant OSPW-related pollutants, if reproduced in a greater range of OSPW.

Occurrences and Behaviors of Naphthenic Acids in a Petroleum Refinery Wastewater Treatment Plant

“…30,33 Furthermore, estrogenic activities in wastewater from different treatment units were determined, since the aromatic NA fraction was reported to have an estrogenic effect. 31,32 Estrogenic activities were not observed in the sample extracts possibly due to the low concentrations of NA mixtures, but antiestrogenic activities were found in wastewater from physicochemical treatment units with ER antagonist potency ranging from 750 to 2100 ng Tamoxifen/L (Figure 4 and SI Figure S5). It should be noted that the antiestrogenic activities disappeared in the A/O process effluent and secondary effluent, suggesting the effective removal of the toxic compounds by the activated sludge system (Figure 4).…”

“…29,30 For example, the aromatic NAs with chemical formulas similar to estrone-and estradiol-like compounds have been demonstrated to cause estrogenicity in fish larvae. 31,32 Several biodegradation studies reported the microorganisms and mechanisms involved in degradation of individual aromatic NA compounds; 30,33 however, there is very little understanding of aromatic NAs in water and solid fractions during physiochemical treatment and activated sludge treatment processes.…”

The value of zebrafish as an integrative model in effect-directed analysis - a review

“…Natural product studies aimed to identify bioactive compounds for pharmacological applications, investigating mostly plant extracts [19,[34][35][36][37][38][39][40][41][42][43][44][45] but also extracts of bacteria [46], cyanobacteria and algae [47], seaweed [48] and marine organisms [49]. Environmental toxicology studies aimed to identify the toxic compounds in various environmental samples, including marine and fluvial sediments [50][51][52], soil [53], cyanobacteria and algae [54,55], industrial effluent [33], rubber tyre leachates [32], oil sand process waters [56,57] and river pore water [58]. Finally, fish skin extracts were investigated in a behavioural sciences study [59].…”

“…Zebrafish up to 5 days post fertilization (dpf ) were the life stages mostly applied, except for experiments that extended the assays up to 6 to 7 dpf [34,49,53,56,57] or a few studies with adults [33,47,59]. Environmental toxicology studies for the most part performed exposure not only in 24-well plates (200 μL to 2 mL per embryo or larva) but also in crystallization dishes, scintillation vials or beakers (450 μL to 5 mL per embryo or larva, 40 to 300 mL per adult), while natural product studies were performed exclusively in multiwell-plate setup (<100 to 250 μL per embryo or larva).…”

Comparative toxicity of selected naphthenic acids, oil sands processed water and surface waters in rainbow trout hepatocytes: A gene expression study

“…These results further support the notion that NAs derived from OS can negatively impact endocrine function in fish and can contribute to long-term toxicity of OSPW. Aromatic NAs were found to weakly induce VTG gene expression in zebra fish larvae [27], suggesting that other types of NAs or other compounds found in OSPW contribute towards estrogenicity or produce effects at the steroid metabolism level, as shown above. It appears that NA endocrine-disrupting effects occur across the brain-gonad-liver axis in fathead minnows exposed to untreated and ozone treated OSPW [28].…”