Aquatic hazard assessment of a commercial sample of naphthenic acids

Many environmental matrices contaminated with organic pollutants derived from crude oil or degraded petroleum contain mixtures so complex that they are typically unresolved by conventional analytical techniques such as gas chromatography. The resulting chromatographic features have become known as 'humps' or unresolved complex mixtures (UCMs). These UCMs often dominate the organic contaminants of polluted environmental samples: for example, in oil sands produced water up to 150mgL of 'naphthenic acids' appear as UCMs when examined by gas chromatography as the esters. In oil-contaminated mussels, aromatic hydrocarbon UCMs may comprise almost all of the total toxic hydrocarbons, with over 7000μgg dry weight reported in some samples. Over the last 25 years, efforts to resolve and thus identify, or at least to produce average structures, for some UCM components, have proved fruitful. Numerous non-polar UCM hydrocarbons and more polar UCM acids have been identified, then synthesised or purchased from commercial suppliers. As UCMs have been proposed to represent a risk to aquatic organisms, the need for assessment of the ecotoxicological effects and characterisation of the mode of action (MoA) of these environmental pollutants has arisen. In the present study, several chemicals with structures typical of those found in some UCMs, were assessed for their potential to disrupt membrane integrity, inhibit metabolic activity, activate the aryl hydrocarbon receptor (AhR), and activate the estrogen receptor (ER) in primary rainbow trout hepatocytes (Oncorhynchus mykiss). These endpoints were determined in order to screen for common toxic modes of action (MoA) in this diverse group of chemicals. The results from the in vitro screening indicated that of the endpoints tested, the predominant toxic MoA was cytotoxicity. EC values for cytotoxicity were obtained for 16 compounds and ranged from 77μM-24mM, whereof aliphatic monocyclic acids, monoaromatic acids, polycyclic monoaromatic acids and alkylnaphthalenes were the most toxic. The observed cytotoxicity of the chemicals correlated well with the hydrophobicity (LogK) suggesting that the toxicity was predominantly due to a non-specific MoA. Interestingly, two compounds induced the ER-mediated production of vitellogenin (Vtg) and six compounds induced the AhR-mediated Ethoxyresorufin-O-deethylase (EROD) enzymatic activity to >20% of the positive control; by doing so suggesting that they may act as ER or AhR agonists in fish. The heterogeneous group of 'UCM compounds' tested exhibited multiple MoA that may potentially cause adverse effects in fish. Additional studies to determine if these compounds may cause adverse effects in vivo at environmentally relevant concentrations, are warranted to identify if such compounds are indeed of potential environmental concern.

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“…NA) and non-polar (e.g. hydrocarbons) (Conly et al, 2002;Headley and McMartin, 2004;Swigert et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

“…GCxGC-MS) has also led to partial resolution (usually following derivatisation) even of UCMs of more polar petroleum constituents, such as petroleum acids (e.g. naphthenic acids (NAs), Bowman et al, 2014;Swigert et al, 2015). Such components become more quantitatively important following biodegradation of petroleum, e.g.…”

Section: Introductionmentioning

confidence: 99%

Toxicity of organic compounds from unresolved complex mixtures (UCMs) to primary fish hepatocytes

et al. 2017

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“…Chemical characterization of commercial NAs revealed that the majority of NAs in commercial mixtures were composed of 1 to 3 rings [29]. These commercial preparations also contain monoaromatic acids and non-acids (both found in the light PAHs fraction), PAHs and sulfur heterocyclic hydrocarbons.…”

Section: Discussionmentioning

confidence: 99%

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

Gagné¹,

André²,

Turcotte³

et al. 2016

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Open Access Research articledeposits and is considered one of the world's largest oil reserves with an estimated yield of 27 billion cubic meters of crude oil [1]. OS consist of about 10% bitumen and 5% water, with the remainder being sand and clay. The extraction process involves adding hot caustic water to OS under aeration to separate bitumen from the OS (Clark extraction process). The crude oil fraction, which partitions at the surface, is then further extracted with the addition of solvents (naphtha, toluene) to yield a more concentrated non-polar fraction. The remaining water and sediment deposits constitute the OSPW, which is released into large tailing ponds covering many square kilometers. Numerous contaminants are found in OSPW, including a number of alkaliextractable compounds such as Naphthenic Acids (NAs), polyaromatic and aliphatic hydrocarbons and various inorganic elements such as sodium, vanadium, strontium, calcium, nickel and sulfates [2][3][4].Recent evidence has shown that OS mining activity was associated with increased releases of dissolved PAHs and heavy metals, which raised concerns about the ecotoxicological consequences of these activities [5][6]. NAs are cyclic aliphatic hydrocarbons that can reach concentrations as high as 50 mg/ L in tailing ponds [7]. NAs follow the C n H 2n-z O x rule which comprise at least one carboxylic acid and they are suspected to be a major component of OSPW toxicity. However, the presence of NAs has been observed in runoff waters (leachates) from OS storage sites, indicating that OSPW is not the only source of NA in the environment [8]. This highlights the difficulty of identifying specific markers of OSPW in the environment at low levels, although the highest concentrations of NAs are found in OSPW.The toxicity of OSPW to aquatic organisms has received increasing attention over the last decade. Toxicity has been examined at various levels, including endocrine disruption, DNA damage, immune competence, biotransformation and reproduction. Goldfish exposed to OSPW for 12 weeks showed elevated expression of pro inflammatorygenes such as interleukin-1β and tumor necrosis factor 2 in the spleen and kidneys [9]. This AbstractThis study examined the cytotoxic properties of selected naphthenic Acids (NA), commercial mixtures of NA in rainbow trout hepatocytes and compares the responses with Oil Sand Processed Water (OSPW) and river water extracts. Hepatocytes were exposed to increasing concentrations of selected NAs (z = 0, 2, 4, 6, 8 and 10), 2 commercial mixtures of NA, 2 OSPW, and surface waters upstream and downstream from the Athabasca River at an OS development area (Alberta, Canada) for 48 h at 15°C. Cell viability, total RNA levels and the expression of 15 gene transcripts involved in biotransformation (CYP1A1, CYP3A4, GST and MDR), oxidative stress (SOD, CAT, GST), DNA damage/repair (UNG, APEX, LIG, GADD45, OGG), estrogenicity (VTG and ER2), cell growth (PCNA, GADD45), and glycolysis (GAPDH) were determined. Individual NAs induced the expression most of t...

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“…Storage of OSPW in close proximity to natural water sources (rivers, ponds, marshes) is of concern due to the possibility of tailings pond leakage and possible seepage into groundwater. Analysis of groundwaters and adjacent natural waters is required in order to monitor for possible leakage, seepage or accidental discharge, as it has been reported that OSPW is toxic to aquatic organisms (Allen, 2008;Marentette et al, 2015;Swigert et al, 2015). The caustic hot water extraction process used to extract the bitumen from the oil sands is known to concentrate the acidic species, namely naphthenic acids (NAs), and related components which are collectively known as naphthenic acid fraction compounds (NAFCs) (Allen, 2008;Headley and McMartin, 2004;Shell Canada Ltd., 2016).…”

Section: Introductionmentioning

confidence: 99%

Characterization of oil sands naphthenic acids by negative-ion electrospray ionization mass spectrometry: Influence of acidic versus basic transfer solvent

et al. 2019

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Aquatic hazard assessment of a commercial sample of naphthenic acids

Cited by 55 publications

References 37 publications

Toxicity of organic compounds from unresolved complex mixtures (UCMs) to primary fish hepatocytes

Toxicity of organic compounds from unresolved complex mixtures (UCMs) to primary fish hepatocytes

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

Characterization of oil sands naphthenic acids by negative-ion electrospray ionization mass spectrometry: Influence of acidic versus basic transfer solvent

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