Thyroid cancer risk associated with perfluoroalkyl carboxylate exposure: Assessment using a human dermal fibroblast-derived extracellular matrix-based thyroid cancer organoid.

The burgeoning incidence of thyroid cancer globally necessitates a deeper understanding of its etiological factors. Emerging research suggests a link to environmental contaminants, notably perfluoroalkyl carboxylates (PFACs). This study introduces a novel biomaterial-based approach for modeling thyroid cancer and assesses PFAC exposure-related health risks. This biomaterial-centric methodology enabled a realistic simulation of long-term, low-dose PFAC exposure, yielding critical insights into their carcinogenic potential. Initially, the no observed adverse effect level concentration of 10 µM for four different PFACs, determined using cytotoxicity tests in 2D cell cultures, was employed with thyroid cancer organoids. Specifically, these organoids were exposed to 10 µM of PFACs, refreshed every 3 days over a period of 21 days. The impact of these PFACs on the organoids was assessed using western blotting and immunofluorescence, complemented by high-content screening imaging. This evaluation focused on thyroid-specific biomarkers, epithelial-mesenchymal transition markers, and the proliferation marker Ki-67. Findings indicated significant alterations in these markers, particularly with long-chain PFACs, suggesting an increased risk of thyroid cancer progression and metastasis upon prolonged exposure. This research advances our understanding of thyroid cancer pathology within the context of environmental health risks by investigating the effects of low-dose, long-term exposure to PFACs on human thyroid cancer organoids. The findings reveal the potential carcinogenic risk associated with these substances, emphasizing the urgent need for stricter regulatory controls.

Do PFCAs drive the establishment of thyroid cancer microenvironment? Effects of C6O4, PFOA and PFHxA exposure in two models of human thyroid cells in primary culture.

BACKGROUND: Exposure to environmental pollutants is suspected to be one of the potential causes accounting for the increase in thyroid cancer (TC) incidence worldwide. Among the ubiquitous pollutants, per-polyfluoroalkyl substances (PFASs), were demonstrated to exert thyroid disrupting effects. Perfluoroalkyl carboxylates (PFCAs) represent a subgroup of PFAS and include perfluoro carboxylic acids (PFOA and PFHxA) and perfluoropolyether carboxylic acid (C6O4). The potential relationship between exposure to PFCAs and TC was not yet fully elucidated. This in vitro study investigated whether certain PFCAs (C6O4, PFOA, and PFHxA) can influence the composition of TC microenvironment. METHODS: Two models of normal thyroid cells in primary cultures: Adherent (A-NHT) and Spheroids (S-NHT) were employed. A-NHT and S-NHT were exposed to C6O4, PFOA or PFHxA (0; 0.01; 0.1, 1; 10; 100; 1000 ng/mL) to assess viability (WST-1 and AV/PI assay), evaluate spherification index (SI) and volume specifically in S-NHT. CXCL8 and CCL2 (mRNA and protein), and EMT-related genes were assessed in both models after exposure to PFCAs. RESULTS: PFHxA reduced the viability of both A-NHT and S-NHT. None of the PFCAs interfered with the volume or spherification process in S-NHT. CXCL8 and CCL2 mRNA and protein levels were differently up-regulated by each PFCAs, being PFOA and PFHxA the stronger inducers. Moreover, among the tested PFCAs, PFHxA induced a more consistent increase in the mRNA levels of EMT-related genes. CONCLUSIONS: This is the first evaluation of the effects of exposure to PFCAs on factors potentially involved in establishing the TC microenvironment. PFHxA modulated the TC microenvironment at three levels: cell viability, pro-tumorigenic chemokines, and EMT-genes. The results provide further evidence of the pro-tumorigenic effect of PFOA. On the other hand, a marginal effect was observed for C6O4 on pro-tumorigenic chemokines.

Uncovering the toxicity mechanisms of a series of carboxylic acids in liver cells through computational and experimental approaches.

Hepatotoxicity poses a significant concern in drug design due to the potential liver damage that can be caused by new drugs. Among common manifestations of hepatotoxic damage is lipid accumulation in hepatic tissue, resulting in liver steatosis or phospholipidosis. Carboxylic derivatives are prone to interfere with fatty acid metabolism and cause lipid accumulation in hepatocytes. This study investigates the toxic behaviour of 24 structurally related carboxylic acids in hepatocytes, specifically their ability to cause accumulation of fatty acids and phospholipids. Using high-content screening (HCS) assays, we identified two distinct lipid accumulation patterns. Subsequently, we developed structure-activity relationship (SAR) and quantitative structure-activity relationship (QSAR) models to determine relevant molecular substructures and descriptors contributing to these adverse effects. Additionally, we calculated physicochemical properties associated with lipid accumulation in hepatocytes and examined their correlation with our chemical structure characteristics. To assess the applicability of our findings to a wide range of chemical compounds, we employed two external datasets to evaluate the distribution of our QSAR descriptors. Our study highlights the significance of subtle molecular structural variations in triggering hepatotoxicity, such as the presence of nitrogen or the specific arrangement of substitutions within the carbon chain. By employing our comprehensive approach, we pinpointed specific molecules and elucidated their mechanisms of toxicity, thus offering valuable insights to guide future toxicology investigations.

Assessment of perfluorocarboxylic acids in fluorinated high-density polyethylene containers and estimation of potential non-cancer risks associated with anticipated use scenarios.

High density polyethylene (HDPE) containers are fluorinated to impart barrier properties that prevent permeation of liquid products filled in the container. The process of fluorination may result in the unintentional formation of certain per- and polyfluoroalkyl substances (PFAS), specifically perfluoroalkyl carboxylic acids (PFCAs), as impurities. This study measured the amounts of PFCAs that may be present in the fluorinated HDPE containers, which could migrate into products stored in these containers. Migration studies were also conducted using water and mineral spirits to estimate the amount of PFCAs that might be found in the products stored in these containers. The migration results were used to conservatively model potential PFCA exposures from use of six product types: indoor-sprayed products, floor products, hand-applied products, manually-sprayed pesticides, hose-end sprayed products, and agricultural (industrial) pesticides. The potential that such uses could result in a non-cancer hazard was assessed by comparing the modeled exposures to both applicable human non-cancer toxicity values and environmental screening levels. Environmental releases were also compared to aquatic and terrestrial predicted no-effect concentrations (PNECs). The results of these analyses indicated no unreasonable non-cancer risk to humans, aquatic species, and terrestrial species from PFCAs in products stored in fluorinated HDPE containers.

Examining the immunotoxicity of oil sands process affected waters using a human macrophage cell line.

Oil sands process affected water (OSPW) is produced during the surface mining of the oil sands bitumen deposits in Northern Alberta. OSPW contains variable quantities of organic and inorganic components causing toxic effects on living organisms. Advanced Oxidation Processes (AOPs) are widely used to degrade toxic organic components from OSPW including naphthenic acids (NAs). However, there is no established biological procedure to assess the effectiveness of the remediation processes. Our previous study showed that human macrophage cells (THP-1) can be used as a bioindicator system to evaluate the effectiveness of OSPW treatments through examining the proinflammatory gene transcription levels. In the present study, we investigated the immunotoxicological changes in THP-1 cells following exposure to untreated and AOP-treated OSPW. Specifically, using proinflammatory cytokine protein secretion assays we showed that AOP treatment significantly abrogates the ability of OSPW to induce the secretion of IL-1ß, IL-6, IL-8, TNF-α, IL-1Ra and MCP-1. By measuring transcriptional activity as well as surface protein expression levels, we also showed that two select immune cell surface markers, CD40 and CD54, were significantly elevated following OSPW exposure. However, AOP treatments abolished the immunostimulatory properties of OSPW to enhance the surface expression of these immune proteins. Finally, a transcriptome-based approach was used to examine the proinflammatory effects of OSPW as well as the abrogation of immunotoxicity following AOP treatments. Overall, this research shows how a human macrophage cell-based biomonitoring system serves as an effective in vitro tool to study the immunotoxicity of OSPW samples before and after targeted remediation strategies.

Synthesis and cytotoxicity evaluation of alpha beta unsaturated carboxylic acids of thiophene analogs by using polymer supported microwave-assisted method.

α- ß unsaturated carboxylic acids containing a heterocyclic moiety is one of the most potent class of bioactive compounds whose speedy generation through novel synthetic techniques has become an enigma for the synthetic chemists. This research project demonstrates a novel method for the synthesis of these compounds using polymer-supported microwave-assisted methodology carried out through one-pot multicomponent reaction. Both soluble and insoluble polymers have been used and their results are comprehensively analyzed. Moreover, the compounds are characterized through spectral analysis like FTIR, GC-MASS, 1HNMR Spectroscopy. The cytotoxicity of synthesized compounds is evaluated through MTT assay using HEPG 2 cells.

The aqueous structural speciation of binary thallium-hydroxycarboxylic acid systems. Structure-chemical (bio)reactivity correlations.

Among transition and non-transition metals, thallium is a unique case of an element which, despite its known toxicity, provides interesting challenges through its biology and chemistry linked to diagnosis of human pathophysiologies. Poised to investigate in-depth the structural and electronic aspects of thallium involvement in physiological processes, the synthetic exploration of aqueous binary systems of Tl(I) with physiological binders from the family of hydroxycarboxylic acids (glycolic, lactic, mandelic and citric acid) was pursued in a pH-specific fashion. The isolated crystalline coordination polymers, emerging from that effort, were physicochemically characterized through elemental analysis, FT-IR, ESI-MS, 1H-/13C-NMR, and X-ray crystallography. The coordination environment of thallium in each molecular Tl(I) assembly, along with lattice dimensionality (2D3D), reflects the contributions of the ligands, collectively exemplifying interactions probed into though BVS and Hirshfeld surface analysis. The results portray a well-defined solid-state and solution profile for all species investigated, thereby providing the basis for their subsequent selection into in vitro biological studies involving the (patho)physiological cell lines 3T3-L1, Saos-2, C2C12, and MCF-7. Biotoxicity profiles, encompassing cell viability, morphology, and cell growth support clearly a concentration-, time-, and cell tissue-specific behavior for the chosen Tl(I) compounds in a structure-specific fashion. Collectively, the chemical experimental data support the biological results in formulating a structure-specific behavior for Tl(I)-hydroxycarboxylato species with respect to biotoxicity mechanisms in a (patho)physiological environment. The accrued knowledge stands as the foreground for further investigation into the relevant biological chemistry of Tl(I) and molecular technologies targeting its sequestration and removal from cellular media.

Chronic exposure to PFO4DA and PFO5DoDA, two perfluoroalkyl ether carboxylic acids (PFECAs), suppresses hepatic stress signals and disturbs glucose and lipid metabolism in male mice.

Perfluoroalkyl ether carboxylic acids (PFECAs), including PFO4DA and PFO5DoDA, have been found in both surface water and volunteer blood samples from polluted regions. However, little knowledge is available on their potential bioaccumulation and health risk. In the present study, the half-lives of PFO4DA and PFO5DoDA in male mouse serum were 24 h and nearly 43 d, respectively, indicating markedly increased difficulty in eliminating PFO5DoDA from the body. After 140 d daily exposure both PFO4DA and PFO5DoDA (10 µg/kg/d) increased body weight. Hepatomegaly was the most sensitive phenomenon after exposure treatment, with occurrence even in the 2 µg/kg/d exposure groups. RNA-seq analysis supported a similar but stronger effect of PFO5DoDA compared with PFO4DA. A wide array of genes involved in stimulus sensing and response were suppressed. In addition to weight gain, hyperglycemia was also observed after treatment. Increased glucose and decreased pyruvate and lactate levels in the liver supported a reduction in glycolysis, consistent with the reduction in the key regulator Pfkfb3. In conclusion, chronic PFO4DA and PFO5DoDA exposure suppressed stress signals and disturbed glucose and lipid metabolism in the liver. The longer serum half-life and stronger hepatic bioaccumulation of PFO5DoDA, at least partially, contributed to its stronger hepatotoxicity than that of PFO4DA.

Structure-Activity Relationship of Antischistosomal Ozonide Carboxylic Acids.

Semisynthetic artemisinins and other bioactive peroxides are best known for their powerful antimalarial activities, and they also show substantial activity against schistosomes-another hemoglobin-degrading pathogen. Building on this discovery, we now describe the initial structure-activity relationship (SAR) of antischistosomal ozonide carboxylic acids OZ418 (2) and OZ165 (3). Irrespective of lipophilicity, these ozonide weak acids have relatively low aqueous solubilities and high protein binding values. Ozonides with para-substituted carboxymethoxy and N-benzylglycine substituents had high antischistosomal efficacies. It was possible to increase solubility, decrease protein binding, and maintain the high antischistosomal activity in mice infected with juvenile and adult Schistosoma mansoni by incorporating a weak base functional group in these compounds. In some cases, adding polar functional groups and heteroatoms to the spiroadamantane substructure increased the solubility and metabolic stability, but in all cases decreased the antischistosomal activity.

Adverse effects of naphthenic acids on reproductive health: A focus on placental trophoblast cells.

There is considerable concern that naphthenic acids (NA) related to oil extraction can negatively impact reproduction in mammals yet the mechanisms are unknown. Since placental dysfunction is central to many adverse pregnancy outcomes, the goal of this study was to determine the effects of NA exposure on placental trophoblast cell function. Htr-8/SVneo cells were exposed to a commercial technical NA mixture (Sigma-Aldrich) for 24 h to assess steroid production, markers of inflammation and oxidative stress. NA treatment significantly altered steroid production; progesterone was decreased at all doses tested, whereas there was a significant increase in testosterone production (125 mg/L only). There were no effects on estradiol production. In addition, NA treatment resulted in increased markers of inflammation (interleukin 1ß and prostaglandin E2) and oxidative damage to lipids and nucleic acids. These findings suggest that it is biologically plausible that NA exposure may contribute to placental dysfunction.

Tolerance and cytotoxicity of naphthenic acids on microorganisms isolated from oil sands process-affected water.

The expansion of oil sands has made remediation of oil sands process-affected water (OSPW) critical. As naphthenic acids (NAs) are the primary contributors to toxicity, remediation is required. Bioremediation by native microorganisms is potentially effective, however, toxicity of NAs towards native microorganisms is poorly understood. The aim of this study was to isolate microorganisms from OSPW, assess tolerance to stressors, including naturally sourced NAs and examine exposure effect of NAs on cell membranes. Microorganisms were isolated from OSPW, including the first reported isolation of a fungus (Trichoderma harzianum) and yeast (Rhodotorula mucilaginosa). Isolates tolerated alkaline pH, high salinity, and NA concentrations far exceeding those typical of OSPW indicating toxic effects of OSPW are likely the result of interactions between OSPW components. Comparisons of toxicity determined that OSPW exhibited higher cytotoxicity than NAs. The fungal isolate was able to grow using commercial NAs as its sole carbon source, indicating high resistance to NAs' cytotoxic effects. Future studies will focus on the organisms' ability to degrade NAs, and subsequent effects on toxicity. Characterization of OSPW constituents should be investigated with focus on the synergistic toxic effects of dissolved compounds. A better understanding of OSPW toxicity would enable more effective and targeted bioremediation schemes by native microorganisms.

Using scrap zero valent iron to replace dissolved iron in the Fenton process for textile wastewater treatment: Optimization and assessment of toxicity and biodegradability.

A Fenton like advanced oxidation process (AOP) employing scrap zerovalent iron (SZVI) and hydrogen peroxide (H2O2) was studied for industrial textile wastewater treatment from a textile manufacturing plant located at Medellín, Colombia (South America). The wastewater effluent studied contains a mixture of organic compounds resistant to conventional treatments. The effect of initial pH and SZVI concentration and H2O2 concentration were studied by a response surface methodology (RSM) Box-Behnken design of experiment (BBD). The combined SZVI/H2O2 process led to reductions of 95% color, 76% of chemical oxygen demand (COD) and 71% of total organic carbon (TOC) at optimal operating conditions of pH = 3, SZVI = 2000 mg/L and [H2O2] = 24.5 mM. Molecular weight distribution measurement (MWD), ultraviolet-visible (UV-Vis) spectroscopy, HPLC, biodegradability and toxicity were used to characterize the pollutants after the treatment process finding that the resulting effluent was polluted mostly by low molecular weight carboxylic acids. A remarkable biodegradability enhancement of the effluent was evidenced by a BOD5/COD ratio increase from 0.22 to 0.4; also, the SZVI/H2O2 process successfully reduced the toxicity from 60% to 20% of dead A. Salina crustaceans.

Individual and combined toxicity of carboxylic acid functionalized multi-walled carbon nanotubes and benzo a pyrene in lung adenocarcinoma cells.

Co-exposure to carboxylic acid functionalized multi-walled carbon nanotubes (F-MWCNTs) and polycyclic aromatic hydrocarbons (PAHs) such as benzo a pyrene (BaP) in ambient air have been reported. Adsorption of BaP to F-MWCNTs can influence combined toxicity. Studying individual toxicity of F-MWCNTs and BaP might give unrealistic data. Limited information is available on the combined toxicity of F-MWCNTs and BaP in human cells. The objective of the present work is to evaluate the toxicity of F-MWCNTs and BaP individually and combined in human lung adenocarcinoma (A549 cells). The in vitro toxicity is evaluated through cell viability, the production of reactive oxygen species (ROS), apoptosis, and the production of 8-OHdG assays. Adsorption of BaP to F-MWCNTs was confirmed using a spectrophotometer. The results indicated that the F-MWCNTs and BaP reduce cell viability individually and produce ROS, apoptosis, and 8-OHdG in exposed cells. Stress oxidative is found to be a mechanism of cytotoxicity for both F-MWCNTs and BaP. Combined exposure to F-MWCNTs and BaP decreases cytotoxicity compared to individual exposure, but the difference is not statistically significant in all toxicity assays; hence, the two-factorial analysis indicated an additive toxic interaction. Adsorption of BaP to F-MWCNTs could mitigate the bioavailability and toxicity of BaP in biological systems. Considering the mixture toxicity of MWCNTs and BaP is required for risk assessment of ambient air contaminants.

Microbial metabolites of proanthocyanidins reduce chemical carcinogen-induced DNA damage in human lung epithelial and fetal hepatic cells in vitro.

Seven selected microbial metabolites of proanthocyanidins (MMP), 3-phenylpropionic, 4-hydroxyphenyl acetic, 3-(4-hydroxyphenyl) propionic, p-coumaric, benzoic acid, pyrogallol (PG), and pyrocatechol (PC) were evaluated for their ability to reduce chemical carcinogen-induced toxicity in human lung epithelial cells (BEAS-2B) and human fetal hepatic cells (WRL-68). Cells pre-treated with MMP were exposed to a known chemical carcinogen, 4-[(acetoxymethyl) nitrosamino]-1-(3-pyridyl)-1-butanone (NNKOAc) to assess MMP-mediated cytoprotection and reduction of DNA damage. PG in BEAS-2B and PC in WRL-68 cells mitigated the NNKOAc-induced cytotoxicity. Pre-incubation of PG depicted significant protection against NNKOAc-induced DNA damage in BEAS-2B cells. PC in WRL-68 cells showed similar activity. To understand the mechanisms of PG- and PC-mediated DNA damage reduction, the effect on DNA damage response (DDR) proteins, cellular reactive oxygen species (ROS), total antioxidant capacity (TAC), glutathione peroxidase (GPx), and caspase activity were studied. PG and PC alter the DDR and may promote ATR-Chk1 and ATM-Chk2 pathways, respectively. Cellular oxidative stress induced by NNKOAc was mitigated by PG and PC through enhanced GPx expression and TAC. PG and PC suppressed the activation of the extrinsic apoptotic pathway (caspase 3 and 8) provoked by NNKOAc. MMP are beneficial in chemoprevention by reducing cellular DNA damage.

Using Quantitative Systems Toxicology to Investigate Observed Species Differences in CKA-Mediated Hepatotoxicity.

CKA, a chemokine receptor antagonist intended for treating inflammatory conditions, produced dose-dependent hepatotoxicity in rats but advanced into the clinic where single doses of CKA up to 600 mg appeared safe in humans. Because existing toxicological platforms used during drug development are not perfectly predictive, a quantitative systems toxicology model investigated the hepatotoxic potential of CKA in humans and rats through in vitro assessments of CKA on mitochondrial respiration, oxidative stress, and bile acid transporters. DILIsym predicted that single doses of CKA caused serum ALT >3xULN in a subset of the simulated rat population, while single doses in a simulated human population did not produce serum ALT elevations. Species differences were largely attributed to differences in liver exposure, but increased sensitivity to inhibition of mitochondrial respiration in the rat also contributed. We conclude that mechanistic modeling can elucidate species differences in the hepatotoxic potential of drug candidates.

Relationship between peroxisome proliferator-activated receptor alpha activity and cellular concentration of 14 perfluoroalkyl substances in HepG2 cells.

Peroxisome proliferator-activated receptor alpha (PPARα) is a molecular target for perfluoroalkyl substances (PFASs). Little is known about the cellular uptake of PFASs and how it affects the PPARα activity. We investigated the relationship between PPARα activity and cellular concentration in HepG2 cells of 14 PFASs, including perfluoroalkyl carboxylates (PFCAs), perfluoroalkyl sulfonates and perfluorooctane sulfonamide (FOSA). Cellular concentrations were determined by high-performance liquid chromatography-tandem mass spectrometry and PPARα activity was determined in transiently transfected cells by reporter gene assay. Cellular uptake of the PFASs was low (0.04-4.1%) with absolute cellular concentrations in the range 4-2500 ng mg-1 protein. Cellular concentration of PFCAs increased with perfluorocarbon chain length up to perfluorododecanoate. PPARα activity of PFCAs increased with chain length up to perfluorooctanoate. The maximum induction of PPARα activity was similar for short-chain (perfluorobutanoate and perfluoropentanoate) and long-chain PFCAs (perfluorododecanoate and perfluorotetradecanoate) (approximately twofold). However, PPARα activities were induced at lower cellular concentrations for the short-chain homologs compared to the long-chain homologs. Perfluorohexanoate, perfluoroheptanoate, perfluorooctanoate, perfluorononanoate (PFNA) and perfluorodecanoate induced PPARα activities >2.5-fold compared to controls. The concentration-response relationships were positive for all the tested compounds, except perfluorooctane sulfonate PFOS and FOSA, and were compound-specific, as demonstrated by differences in the estimated slopes. The relationships were steeper for PFCAs with chain lengths up to and including PFNA than for the other studied PFASs. To our knowledge, this is the first report establishing relationships between PPARα activity and cellular concentration of a broad range of PFASs.

Single-walled carbon nanotubes (SWCNTs) inhibit heat shock protein 90 (HSP90) signaling in human lung fibroblasts and keratinocytes.

Single-walled carbon nanotubes (SWCNTs) are carbon-based nanomaterials that possess immense industrial potential. Despite accumulating evidence that exposure to SWCNTs might be toxic to humans, our understanding of the mechanisms for cellular toxicity of SWCNTs remain limited. Here, we demonstrated that acute exposure of short (1-3µm) and regular-length (5-30µm) pristine, carboxylated or hydroxylated SWCNTs inhibited cell proliferation in human somatic and human stem cells in a cell type-dependent manner. The toxicity of regular-length pristine SWCNT was most evidenced in NP69>CYT00086>MCF-10A>MRC-5>HaCaT > HEK-293T>HepG2. In contrast, the short pristine SWCNTs were relatively less toxic in most of the cells being tested, except for NP69 which is more sensitive to short pristine SWCNTs as compared to regular-length pristine SWCNTs. Interestingly, carboxylation and hydroxylation of regular-length SWCNTs, but not the short SWCNTs, significantly reduced the cytotoxicity. Exposure of SWCNTs also induced caspase 3 and 9 activities, mitochondrial membrane depolarization, and significant apoptosis and necrosis in MRC-5 embryonic lung fibroblasts. In contrast, SWCNTs inhibited the proliferation of HaCaT human keratinocytes without inducing cell death. Further analyses by gene expression profiling and Connectivity Map analysis showed that SWCNTs induced a gene expression signature characteristic of heat shock protein 90 (HSP90) inhibition in MRC-5 cells, suggesting that SWCNTs may inhibit the HSP90 signaling pathway. Indeed, exposure of MRC-5 cells to SWCNTs results in a dose-dependent decrease in HSP90 client proteins (AKT, CDK4 and BCL2) and a concomitant increase in HSP70 expression. In addition, SWCNTs also significantly inhibited HSP90-dependent protein refolding. Finally, we showed that ectopic expression of HSP90, but not HSP40 or HSP70, completely abrogated the cytotoxic effects of SWCNTs, suggesting that SWCNT-induced cellular toxicity is HSP90 dependent. In summary, our findings suggest that the toxic effects of SWCNTs are mediated through inhibition of HSP90 in human lung fibroblasts and keratinocytes.

The toxicity of oil sands process-affected water (OSPW): A critical review.

Large volumes of oil sands process-affected water (OSPW) are produced by the surface-mining oil sands industry in Alberta. Both laboratory and field studies have demonstrated that the exposure to OSPW leads to many physiological changes in a variety of organisms. Adverse effects include compromised immunological function, developmental delays, impaired reproduction, disrupted endocrine system, and higher prevalence of tissue-specific pathological manifestations. The composition of OSPW varies with several factors such as ore sources, mining process, and tailings management practices. Differences in water characteristics have confounded interpretation or comparison of OSPW toxicity across studies. Research on individual fractions extracted from OSPW has helped identify some target pollutants. Naphthenic acids (NAs) are considered as the major toxic components in OSPW, exhibiting toxic effects through multiple modes of action including narcosis and endocrine disruption. Other pollutants, like polycyclic aromatic hydrocarbons (PAHs), metals, and ions may also contribute to the overall OSPW toxicity. Studies have been conducted on OSPW as a whole complex effluent mixture, with consideration of the presence of unidentified components, and the interactions (potential synergistic or antagonistic reactions) among chemicals. This review summarizes the toxicological data derived from in vitro and in vivo exposure studies using different OSPW types, and different taxa of organisms. In general, toxicity of OSPW was found to be dependent on the OSPW type and concentration, duration of exposures (acute versus sub chronic), and organism studied.

Using ultrahigh-resolution mass spectrometry and toxicity identification techniques to characterize the toxicity of oil sands process-affected water: The case for classical naphthenic acids.

Previous assessments of oil sands process-affected water (OSPW) toxicity were hampered by lack of high-resolution analytical analysis, use of nonstandard toxicity methods, and variability between OSPW samples. We integrated ultrahigh-resolution mass spectrometry with a toxicity identification evaluation (TIE) approach to quantitatively identify the primary cause of acute toxicity of OSPW to rainbow trout (Oncorhynchus mykiss). The initial characterization of OSPW toxicity indicated that toxicity was associated with nonpolar organic compounds, and toxicant(s) were further isolated within a range of discrete methanol fractions that were then subjected to Orbitrap mass spectrometry to evaluate the contribution of naphthenic acid fraction compounds to toxicity. The results showed that toxicity was attributable to classical naphthenic acids, with the potency of individual compounds increasing as a function of carbon number. Notably, the mass of classical naphthenic acids present in OSPW was dominated by carbon numbers ≤16; however, toxicity was largely a function of classical naphthenic acids with ≥17 carbons. Additional experiments found that acute toxicity of the organic fraction was similar when tested at conductivities of 400 and 1800 µmhos/cm and that rainbow trout fry were more sensitive to the organic fraction than larval fathead minnows (Pimephales promelas). Collectively, the results will aid in developing treatment goals and targets for removal of OSPW toxicity in water return scenarios both during operations and on mine closure. Environ Toxicol Chem 2017;36:3148-3157. © 2017 SETAC.

Toxicity of naphthenic acids to invertebrates: Extracts from oil sands process-affected water versus commercial mixtures.

The toxicity of oil sands process-affected water (OSPW) has been primarily attributed to polar organic constituents, including naphthenic acid fraction components (NAFCs). Our objective was to assess the toxicity of NAFCs derived from fresh and aged OSPW, as well as commercial naphthenic acid (NA) mixtures. Exposures were conducted with three aquatic species: Hyalella azteca (freshwater amphipod), Vibrio fischeri (marine bacterium, Microtox® assay), and Lampsilis cardium (freshwater mussel larvae (glochidia)). Commercial NAs were more toxic than NAFCs, with differences of up to 30-, 4-, and 120-fold for H. azteca, V. fischeri, and L. cardium, respectively, demonstrating that commercial NAs are not reliable surrogates for assessing the toxicity of NAFCs. Differences in toxicity between species were striking for both commercial NAs and NAFCs. Overall, V. fischeri was the least sensitive and H. azteca was the most sensitive organism. Responses of V. fischeri and H. azteca to NAFC exposures were consistent (< 2-fold difference) regardless of source and age of OSPW; however, effects on L. cardium ranged 17-fold between NAFCs. NAFCs derived from fresh OSPW sources were similarly or less toxic to those from aged OSPW. Our results support the need to better characterize the complex mixtures associated with bitumen-influenced waters, both chemically and toxicologically.