Effects of diluted bitumen exposure on the survival, physiology, and behaviour of zebra finches (Taeniopygia guttata).

Diluted bitumen (dilbit) is an unconventional crude petroleum increasingly being extracted and transported to market by pipeline and tanker. Despite the transport of dilbit through terrestrial, aquatic, and coastal habitat important to diverse bird fauna, toxicity data are currently only available for fish and invertebrates. We used the zebra finch (Taeniopygia guttata) as a tractable, avian model system to investigate exposure effects of lightly weathered Cold Lake blend dilbit on survival, tissue residue, and a range of physiological and behavioural endpoints. Birds were exposed via oral gavage over 14-days with dosages of 0, 2, 4, 6, 8, 10, or 12 mL dilbit/kg bw/day. We identified an LD50 of 9.4 mL/kg/d dilbit, with complete mortality at 12 mL/kg/d. Mortality was associated with mass loss, external oiling, decreased pectoral and heart mass, and increased liver mass. Hepatic ethoxyresorufin-O-deethylase activity (EROD) was elevated in all dilbit-dosed birds compared with controls but there was limited evidence of sublethal effects of dilbit on physiological endpoints at doses < 10 mL/kg/d (hematocrit, hemoglobin, total antioxidants, and reactive oxygen metabolites). Dilbit exposure affected behavior, with more dilbit-treated birds foraging away from the feeder, more birds sleeping or idle at low dilbit doses, and fewer birds huddling together at high dilbit doses. Naphthalene, dibenzothiophene, and their alkylated congeners in particular (e.g. C2-napthalene and C2-dibenzothiophene) accumulated in the liver at greater concentrations in dilbit-treated birds compared to controls. Although directly comparable studies in the zebra finch are limited, our mortality data suggest that dilbit is more toxic than the well-studied MC252 conventional light crude oil with this exposure regime. A lack of overt sublethal effects at lower doses, but effects on body mass and composition, behaviour, high mortality, and elevated PAC residue at doses ≥ 10 mL/kg/d suggest a threshold effect.

An Emerging Cross-Species Marker for Organismal Health: Tryptophan-Kynurenine Pathway.

Tryptophan (TRP) is an essential dietary amino acid that, unless otherwise committed to protein synthesis, undergoes metabolism via the Tryptophan-Kynurenine (TRP-KYN) pathway in vertebrate organisms. TRP and its metabolites have key roles in diverse physiological processes including cell growth and maintenance, immunity, disease states and the coordination of adaptive responses to environmental and dietary cues. Changes in TRP metabolism can alter the availability of TRP for protein and serotonin biosynthesis as well as alter levels of the immune-active KYN pathway metabolites. There is now considerable evidence which has shown that the TRP-KYN pathway can be influenced by various stressors including glucocorticoids (marker of chronic stress), infection, inflammation and oxidative stress, and environmental toxicants. While there is little known regarding the role of TRP metabolism following exposure to environmental contaminants, there is evidence of linkages between chemically induced metabolic perturbations and altered TRP enzymes and KYN metabolites. Moreover, the TRP-KYN pathway is conserved across vertebrate species and can be influenced by exposure to xenobiotics, therefore, understanding how this pathway is regulated may have broader implications for environmental and wildlife toxicology. The goal of this narrative review is to (1) identify key pathways affecting Trp-Kyn metabolism in vertebrates and (2) highlight consequences of altered tryptophan metabolism in mammals, birds, amphibians, and fish. We discuss current literature available across species, highlight gaps in the current state of knowledge, and further postulate that the kynurenine to tryptophan ratio can be used as a novel biomarker for assessing organismal and, more broadly, ecosystem health.

A review of 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane in the environment and assessment of its persistence, bioaccumulation and toxicity.

Following the ban of many historically-used flame retardants (FRs), numerous replacement chemicals have been produced and used in products, with some being identified as environmental contaminants. One of these replacement flame retardants is 1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (DBE-DBCH; formerly abbreviated as TBECH), which to date has not been identified for risk assessment and potential regulation. DBE-DBCH technical mixtures consist largely of α- and ß-diastereomers with trace amounts of γ- and δ-DBE-DBCH. The α- and ß-isomers are known contaminants in various environmental media. While current global use and production volumes of DBE-DBCH are unknown, recent studies identified that DBE-DBCH concentrations were among the highest of the measured bromine-based FRs in indoor and urban air in Europe. Yet our mass balance fugacity model and modeling of the physical-chemical properties of DBE-DBCH estimated only 1% partitioning to air with a half-life of 2.2 d atmospherically. In contrast, our modeling characterized DBE-DBCH adsorbing strongly to suspended particulates in the water column (~12%), settling onto sediment (2.5%) with minimal volatilization, but with most partitioning and adsorbing strongly to soil (~85%) with negligible volatilization and slow biodegradation. Our modeling further predicted that organisms would be exposed to DBE-DBCH through partitioning from the dissolved aquatic phase, soil, and by diet, and given its estimated logKow (5.24) and a half-life of 1.7 d in fish, DBE-DBCH is expected to bioaccumulate into lipophilic tissues. Low concentrations of DBE-DBCH are commonly measured in biota and humans, possibly because evidence suggests rapid metabolism. Yet toxicological effects are evident at low exposure concentrations: DBE-DBCH is a proven endocrine disruptor of sex and thyroid hormone pathways, with in vivo toxic effects on reproductive, metabolic, and other endpoints. The objectives of this review are to identify the current state of knowledge concerning DBE-DBCH through an evaluation of its persistence, potential for bioaccumulation, and characterization of its toxicity, while identifying areas for future research.

Validation of a simultaneous method for determining polycyclic aromatic compounds and alkylated isomers in biota.

RATIONALE: There is a need for a validated method to improve detection limits and simultaneously quantify polycyclic aromatic compounds (PACs, both parent and alkylated homologues) in biota by gas chromatography/tandem mass spectrometry because of their environmental significance. The validation of the method was performed in accordance to the Eurachem Guide to Quality in Analytical Chemistry. METHODS: Gas chromatography coupled with a triple quadrupole mass spectrometer used in multiple reaction monitoring (MRM) mode was used for detection and quantification. Retention time windows and selective MRM ion transitions were optimized for a suite of PACs. The developed method was validated by comparing our measurements made on a reference material of freeze-dried mussel tissue (Mytilus edulis) with the certified values. RESULTS: Linearity was observed between 10-1000 pg/µL (PAHs) and 2-500 pg/µL (alkyl-PACs including S-based PACs). The overall mean (±SD) for the limits of detection of 43 PACs studied were 0.305 ± 0.276 and 2.69 ± 1.10 ng/g, respectively. For the 14 certified target analytes, the percent relative error ranged from 1.3 to 33%. With the exception of benzo(a)pyrene, the between-day and within-day repeatability for all target analytes was lower than 15% RSD. CONCLUSIONS: This is the first report of a fully validated method to simultaneously quantify PACs in biota performed in an ISO accredited laboratory.

Impacts of Unregulated Novel Brominated Flame Retardants on Human Liver Thyroid Deiodination and Sulfotransferation.

The inhibitory effects of five novel brominated flame retardants, 1,2-bis(2,4,5-tribromophenoxy)ethane (BTBPE), decabromodiphenylethane (DBDPE), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB), bis(2-ethylhexyl)tetrabromophthalate (BEH-TEBP), and ß-tetrabromoethylcyclohexane (ß-TBECH), on thyroid hormone deiodinase (DIO) and sulfotransferase (SULT) activity were investigated using human in vitro liver microsomal and cytosolic bioassays. Enzymatic activity was measured by incubating active human liver subcellular fractions with thyroid hormones (T4 and rT3 separately) and measuring changes in thyroid hormone (T4, T3, rT3, and 3,3'-T2) concentrations. Only DBDPE showed inhibition of both outer and inner ring deiodination (O and IRD) of T3 and 3,3'-T2 formation from T4, respectively, with an estimated IC50 of 160 nM; no statistically significant inhibition of SULT activity was observed. ORD inhibition of 3,3'-T2 formation from rT3 was also observed (IC50 ∼ 100 nM). The kinetics of T4 O and IRD were also investigated, although a definitive mechanism could not be identified as the Michaelis-Menten parameters and maximal rate constants were not significantly different. Concentrations tested were intentionally above expected environmental levels, and this study suggests that these NBFRs are not potent human liver DIO and SULT inhibitors. To our knowledge, DBDPE is the first example of a nonhydroxylated contaminant inhibiting DIO activity, and further study of the mechanism of action is warranted.

Evidence for Anaerobic Dechlorination of Dechlorane Plus in Sewage Sludge.

The environmental occurrence of dechlorination moieties from the high production volume flame retardant, Dechlorane Plus (DP), has largely been documented; however, the sources have yet to be well understood. In addition, few laboratory-based studies exist which identify the cause for the occurrence of these chemicals in the environment or humans. Anaerobic dechlorination of the two DP isomers was investigated using a laboratory-simulated wastewater treatment plant (WWTP) environment where anaerobic digestion is used as part of the treatment regime. Known amounts of each isomer were added separately to sewage sludge which provided the electron-donating substrate and at prescribed time points in the incubation, a portion of the media was removed and analyzed for DP and any dechlorination metabolites. After 7 days, monohydrodechlorinated products were observed for both the syn- and anti-DP which were continued throughout the duration of our study (49 days) in an increasing manner giving a calculated formation rate of 0.48 ± 0.09 and 0.79 ± 0.12 pmols/day for syn- and anti-DP, respectively. Furthermore, we observed a second monohydrodechlorinated product only in the anti-DP isomer incubation medium. This strongly suggests that anti-DP is more susceptible to anaerobic degradation than the syn isomer. We also provide compelling evidence to the location of chlorine loss in the dechlorination DP analogues. Finally, the dechlorination DP moieties formed in our study matched the retention times and identification of those observed in surficial sediment located downstream of the WWTP.

Polycyclic aromatic hydrocarbon metabolites in Arctic cod (Boreogadus saida) from the Beaufort Sea and associative fish health effects.

In 2012, Arctic cod (Boreogadus saida) were collected from offshore regions of the Beaufort Sea to determine the concentrations of CYP1A1 phase I metabolites of polycyclic aromatic hydrocarbons (OH-PAHs) in liver and to correlate measured concentrations with (i) morphometric measurements that are known to be indicative of fish health and, (ii) biochemical end points of health including vitamin A/E and metabolites and hepatic deiodinase activity (DI). Four ring OH-PAHs were detected in 90% of our samples with a mean liver concentration of 1829.2 ± 159.2 ng/g (ww). Total (∑) concentrations of 5/6-membered ring OH-PAHs in liver were smaller [mean of 931.6 ± 104.3 ng/g, (ww)] and detected less frequently (75%) than the 4-ring OH-PAHs. Fish length and liver weight were both negatively correlated to ∑ concentrations of 4-ringed OH-PAHs (p < 0.001). Liver somatic index was also negatively correlated to ∑4-OH-PAHs (p < 0.05) but not for ∑5/6-OH-PAHs (p > 0.1). There was a significant positive relationship between DI and 4-ring OH-PAHs (p < 0.05) in liver, suggesting an induction of this enzyme. No such correlation was observed for the 5/6-ring OH-PAHs. Retinyl palmitate (RP) was the only vitamin that could be measured in liver ranging from 0.230 to 26.3 ug/g (ww). No associations between RP and levels of the 4- or 5/6-ringed OH-PAHs were observed. Continued baseline studies are clearly warranted to further understand effects of OH-PAHs on fish health before planned exploration activities begin in this region.

A validated approach for analysis of heterocyclic aromatic compounds in sediment samples.

The scientific literature is replete with analytical methods for the analysis of homocyclic aromatic compounds especially polycyclic aromatic hydrocarbons and their alkylated analogs. However, there is a paucity of methods for the analysis of nitrogen-, sulfur- and oxygen-containing polycyclic aromatic compounds (PACs). The lack of commercially available analytical standards, the presence of many structural derivatives and isomers and lack of certified reference materials all contribute to the inherent challenges in measuring these compounds. Gas chromatography coupled with a tandem mass spectrometer was used to develop two multiple reaction monitoring methods to detect and quantify fifty-three non-halogenated and halogenated hetero-polycyclic aromatic compounds (HPACs). Because of their greater polarity, strongly non-polar solvents typically employed to extract homocyclic PACs from sediment samples did not yield acceptable recoveries of our target analytes. By adding ethyl acetate to dichloromethane (50:50), recoveries of our target analytes using accelerated solvent extraction increased markedly. The performance characteristics of the validated method including accuracy [> than 67% for 46 (out of 53) analytes], inter- and intra-day precision [<30% for all analytes, (expressed as relative standard deviation)], limits of detection (0.1 to 2.3 ng/g) and quantitation (1.5 to 7.6 ng/g) imply that the method is fit for its intended purpose. A sediment sample from a known contaminated site in Canada was analyzed for both homo- and hetero-PACs. Measured concentrations of Σ27HPAC (7.3 µg/g, dry weight) were significantly smaller (p<0.05) than Σ16PAHs (80.9 µg/g, dry weight) and Σ30Alkylated-PAHs (14.2 µg/g, dry weight). These results suggest that the developed method is an effective and efficient approach for the targeted analysis of HPACs and their halogenated derivatives in sediment samples.

Scavenging amphipods: sentinels for penetration of mercury and persistent organic chemicals into food webs of the deep Arctic Ocean.

Archived specimens of the scavenging amphipod Eurythenes gryllus, collected from 2075 to 4250 m below the surface on five expeditions to the western and central Arctic Ocean between 1983 and 1998, were analyzed for total mercury (∑Hg), methyl mercury (MeHg), polychlorinated biphenyls (PCBs) and other industrial or byproduct organochlorines (chlorobenzenes, pentachloroanisole, octachlorostyrene), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs). Median ∑Hg concentrations ranged from 70 to 366 ng g(-1) wet weight (ww). MeHg concentrations (3.55 to 23.5 ng g(-1) ww) accounted for 1.7 to 20.1% (median 3.7%) of ∑Hg. ∑Hg and MeHg were positively and significantly correlated with ww (∑Hg r(2) = 0.18, p = 0.0004, n = 63; MeHg r(2) = 0.42, p = 0.0004, n = 25), but not significantly with δ(13)C nor δ(15)N. Median concentrations of total persistent organic pollutants (POPs) ranged from 9750 to 156,000 ng g(-1) lipid weight, with order of abundance: ∑TOX (chlorobornanes quantified as technical toxaphene) > ∑PCBs > ∑DDTs > ∑chlordanes > ∑mirex compounds > ∑BDEs ∼ ∑chlorobenzenes ∼ octachlorostyrene > α-hexachlorocyclohexane ∼ hexachlorobenzene ∼ pentachloroanisole. Enantioselective accumulation was found for the chiral OCPs o,p'-DDT, cis- and trans-chlordane, nonachlor MC6 and oxychlordane. Lipid-normalized POPs concentrations were elevated in amphipods with lipid percentages ≤10%, suggesting that utilization of lipids resulted in concentration of POPs in the remaining lipid pool. Multidimensional Scaling (MDS) analysis using log-transformed physiological variables and lipid-normalized organochlorine concentrations distinguished amphipods from the central vs western arctic stations. This distinction was also seen for PCB homologues, whereas profiles of other compound classes were more related to specific stations rather than central-west differences.

Polycyclic aromatic compound and trace metal element residues in Mytilus mussels at marine wildlife hotspots on the Pacific coast of Canada.

The Pacific coast of Canada has a rich marine fauna and a growing human population with increasing potential for pollution releases, but there is currently little overlap between marine wildlife hotspots and ongoing biomonitoring efforts for less bioaccumulative contaminants such as polycyclic aromatic compounds (PAC) and trace metals (metals). We surveyed PACs and metals at marine bird breeding colonies in coastal British Columbia in 2018 by analyzing chemical residues in the soft tissue of bivalve Mytilus sp. mussels collected from stations (n = 3) at seven sites. The concentration of sum PACs (∑43PAC) and high molecular weight (HMW) PACs were highest at the Second Narrows colony in Vancouver Harbour, a highly urbanized and industrialized port within the Salish Sea. For conservation areas, two Salish Sea and three Pacific Ocean coast colonies, PACs were generally lower. However, ∑43PAC, ∑HMWPAC, and several HMW congeners at the remote site of Triangle Island, a Marine National Wildlife Area, were not significantly different from Second Narrows. The dominant PAC sources at all sites are likely pyrogenic rather than petrogenic, as suggested by PAC profiles, proportion of parent PACs, and source-indicator congeners. For metals, site differences were found for seven out of eight priority metals, but principal component analysis indicated that site differences, such as high mercury and cadmium at offshore sites, are likely related to environmental and biological variables including salinity, condition index, water temperature, and shell length. Our survey across a broad coastal region shows that PAC and metal biomonitoring programs with mussels should include wildlife hotspots where the exposure of protected vertebrate species to pollutants with low bioaccumulation potential would be less obvious, and shows that collection of data on key covariates (e.g. lipid content, salinity) will be critical to tracking long-term trends and detecting pollution release events.

Microbead beating extraction of avian eggs for polycyclic aromatic compounds.

Due to their relatively high trophic position and importance as a food source for many communities in the circumpolar north, seabird eggs are an important matrix for monitoring contaminant levels. In fact, many countries, including Canada, have established long-term seabird egg contaminant monitoring programs, with oil related compounds a contaminant of emerging concern for seabirds in several regions. Current approaches to measuring many contaminant burdens in seabird eggs are time-consuming and often require large volumes of solvent. Here we propose an alternative approach, based on the principle of microbead beating tissue extraction using custom designed stainless-steel extraction tubes and lids, to measure a suite of 75 polycyclic aromatic compounds (polycyclic aromatic hydrocarbons (PAHs), alkyl-PAHs, halogenated-PAHs and some heterocyclic compounds) comprising a wide-range of chemical properties. Our method was conducted in strict accordance with ISO/IEC 17025 guidelines for method validation. Accuracies for our analytes generally ranged from 70 - 120%, and intra and inter-day repeatability for most analytes were < 30%. Limits of detection/quantitation for the 75 target analytes were < 0.2/0.6 ng g-1. The level of contamination in our method blanks was significantly smaller in our stainless-steel tubes/lids relative to commercially available high-density plastic alternatives. Overall, our method meets our data quality objectives and results in a notable reduction in sample processing times relative to current approaches.

Trophic transfer of contaminants in a changing arctic marine food web: Cumberland Sound, Nunavut, Canada.

Contaminant dynamics in arctic marine food webs may be impacted by current climate-induced food web changes including increases in transient/subarctic species. We quantified food web organochlorine transfer in the Cumberland Sound (Nunavut, Canada) arctic marine food web in the presence of transient species using species-specific biomagnification factors (BMFs), trophic magnification factors (TMFs), and a multifactor model that included δ(15)N-derived trophic position and species habitat range (transient versus resident), and also considered δ(13)C-derived carbon source, thermoregulatory group, and season. Transient/subarctic species relative to residents had higher prey-to-predator BMFs of biomagnifying contaminants (1.4 to 62 for harp seal, Greenland shark, and narwhal versus 1.1 to 20 for ringed seal, arctic skate, and beluga whale, respectively). For contaminants that biomagnified in a transient-and-resident food web and a resident-only food web scenario, TMFs were higher in the former (2.3 to 10.1) versus the latter (1.7 to 4.0). Transient/subarctic species have higher tissue contaminant levels and greater BMFs likely due to higher energetic requirements associated with long-distance movements or consumption of more contaminated prey in regions outside of Cumberland Sound. These results demonstrate that, in addition to climate change-related long-range transport/deposition/revolatilization changes, increasing numbers of transient/subarctic animals may alter food web contaminant dynamics.

Identification and determination of the dechlorination products of Dechlorane 602 in Great Lakes fish and Arctic beluga whales by gas chromatography-high resolution mass spectrometry.

During the course of our studies of in-use chlorinated flame retardants, such as Dechlorane Plus(®) and Dechloranes 602 and 604, blubber of beluga whales from the Canadian Arctic and lake trout and whitefish from the North American Great Lakes were found to contain two novel dechlorination products of Dechlorane 602 (Dec602). The structures of these compounds were characterized by experiments performed using both gas chromatography-high resolution mass spectrometry and Fourier transform mass spectrometry with a prepared technical mixture of monohydro and dihydroDec602 derivatives. These Dec602 derivatives are analogous to the well-known monohydro and dihydro photochemical degradation products of Mirex. The ratio of the two monohydroDec602 diastereomers varied between Lake Ontario fish and those from the upper lakes, but only one isomer was found in Arctic beluga, indicating that one isomer is either more stable or more bioaccumulative. Dechlorane Plus(®), Dec603, and Dec 604 were not detected in Arctic beluga, but Dec602 and its monohydroDec602 derivative were measured in approximately equal concentrations, ranging from 25 to 300 pg/g lipid. In Great Lakes fish, concentrations of the monohydroDec602 derivatives were also close to those of Dec602, ranging from 2 to 67 ng/g lipid and were greatest in Lake Ontario. This study reports on the first measurements of dechlorane-related compounds in Arctic biota and the first detection of monohydroDec602 degradation products and their accumulation in biota.

Alkylation of Benz[a]anthracene Affects Toxicity to Early-Life Stage Zebrafish and In Vitro Aryl Hydrocarbon Receptor 2 Transactivation in a Position-Dependent Manner.

Polycyclic aromatic hydrocarbons (PAHs) are structurally diverse organic chemicals that can have adverse effects on the health of fishes through activation of aryl hydrocarbon receptor 2 (AhR2). They are ubiquitous in the environment, but alkyl PAHs are more abundant in some environmental matrices. However, relatively little is known regarding the effects of alkylation on the toxicity of PAHs to fishes in vivo and how this relates to potency for activation of AhR2 in vitro. Therefore, the objectives of the present study were to determine the toxicity of benz[a]anthracene and three alkylated homologs representing various alkylation positions to early life stages of zebrafish (Danio rerio) and to assess the potency of each for activation of the zebrafish AhR2 in a standardized in vitro AhR transactivation assay. Exposure of embryos to each of the PAHs caused a dose-dependent increase in mortality and malformations characteristic of AhR2 activation. Each alkyl homolog had in vivo toxicities and in vitro AhR2 activation potencies different from those of the parent PAH in a position-dependent manner. However, there was no statistically significant linear relationship between responses measured in these assays. The results suggest a need for further investigation into the effect of alkylation on the toxicity of PAHs to fishes and greater consideration of the contribution of alkylated homologs in ecological risk assessments. Environ Toxicol Chem 2022;41:1993-2002. © 2022 SETAC.

Effects of Avian Eggshell Oiling With Diluted Bitumen Show Sublethal Embryonic Polycyclic Aromatic Compound Exposure.

Breeding birds that become oiled may contaminate the shells of their eggs, and studies of conventional crude oil suggest that even small quantities can be absorbed through the eggshell and cause embryotoxicity. Unconventional crude oils remain untested, so we evaluated whether a major Canadian oil sands product, diluted bitumen (dilbit), would be absorbed and cause toxicity when applied to eggshells of two species, domestic chicken (Gallus gallus domesticus) and double-crested cormorant (Nannopterum auritum). We artificially incubated eggs and applied lightly weathered dilbit (Cold Lake blend) to the eggshells (0.015-0.15 mg g-1 egg in chicken; 0.1-0.4 mg g-1 egg in cormorant) at various points during incubation before sampling prehatch embryos. Polycyclic aromatic compound (PAC) residue in cormorant embryos was elevated only at the highest dilbit application (0.4 mg g-1 egg) closest (day 16) to sampling on day 22. In contrast, cormorant liver cytochrome P450 1a4 (Cyp1a4) mRNA expression (quantitative polymerase chain reaction assay) was elevated only in embryos treated with the earliest and lowest dilbit application (0.1 mg g-1 egg on day 4). These results confirm that dilbit can cross through the eggshell and be absorbed by embryos, and they imply rapid biotransformation of PACs and a nonmonotonic Cyp1a4 response. Despite evidence of exposure in cormorant, we found no detectable effects on the frequency of survival, deformity, and gross lesions, nor did we find effects on physiological endpoints indicative of growth and cardiovascular function in either chicken or cormorant. In ovo dilbit exposure may be less toxic than well-studied conventional crude oils. The effects of an oil spill scenario involving dilbit to bird embryos might be subtle, and PACs may be rapidly metabolized. Environ Toxicol Chem 2022;41:159-174. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Kynurenine to tryptophan ratio as a biomarker of acute stress in fish.

The aim of this study was to determine the kynurenine (KYN) to tryptophan (TRP) ratio (KTR) in fish tissue to assess its usefulness as a biomarker of acute stress. Laboratory held rainbow trout (Oncorhynchus mykiss) were subjected to an acute stressor and KYN, TRP and cortisol were measured in liver and brain tissues at 4- and 48-h post-stress. The analytical method used to determine our analytes was based on lyophilization, and liquid-solid extraction followed by isotope dilution high-performance liquid chromatography positive ion electrospray tandem mass spectrometry. The [KYN]/[TRP] ratio (KTR) was greater in fish liver and brain in the 48-h post-stress exposure group (n = 8) relative to controls (n = 8, p < 0.05); a similar increase was not observed in fish in the 4-h post-stress exposure group. Hepatic and brain cortisol levels were also elevated in fish from both stress-induced groups relative to their respective controls implying that cortisol responded more quickly to the stressful stimulus than KYN and TRP. Our results suggest that the KTR is a promising acute stress diagnostic biomarker in fish. Efforts are ongoing to assess whether the KTR can be used as a biomarker for chronic stress in fish exposed to aquatic contaminants and other environmental stressors and if similar assessments can be made on tissues collected via non-lethal approaches.

Hexabromocyclododecane: current understanding of chemistry, environmental fate and toxicology and implications for global management.

Hexabromocyclododecane (HBCD) is a globally produced brominated flame retardant (BFR) used primarily as an additive FR in polystyrene and textile products and has been the subject of intensified research, monitoring and regulatory interest over the past decade. HBCD is currently being evaluated under the Stockholm Convention on Persistent Organic Pollutants. HBCD is hydrophobic (i.e., has low water solubility) and thus partitions to organic phases in the aquatic environment (e.g., lipids, suspended solids). It is ubiquitous in the global environment with monitoring data generally exhibiting the expected relationship between proximity to known sources and levels; however, temporal trends are not consistent. Estimated degradation half-lives, together with data in abiotic compartments and long-range transport potential indicate HBCD may be sufficiently persistent and distributed to be of global concern. The detection of HBCD in biota in the Arctic and in source regions and available bioaccumulation data also support the case for regulatory scrutiny. Toxicity testing has detected reproductive, developmental and behavioral effects in animals where exposures are sufficient. Recent toxicological advances include a better mechanistic understanding of how HBCD can interfere with the hypothalamic-pituitary-thyroid axis, affect normal development, and impact the central nervous system; however, levels in biota in remote locations are below known effects thresholds. For many regulatory criteria, there are substantial uncertainties that reduce confidence in evaluations and thereby confound management decision-making based on currently available information.

Historic trends of dechloranes 602, 603, 604, dechlorane plus and other norbornene derivatives and their bioaccumulation potential in lake ontario.

Temporal trends and seasonal variation of Dechloranes (Dec) 602, 603, 604, and Chlordene Plus (CP) in Niagara River suspended sediment, a Lake Ontario sediment core, and Lake Ontario lake trout were investigated, with Mirex and Dechlorane Plus (DP) included for comparison. Temporal concentration trends were generally consistent in each of the media for all compounds with the lowest concentrations observed in or after the late 1990s. In Niagara River suspended sediments, all compounds showed seasonal variation over a year with distinct profiles observed. The relative concentration patterns observed were total DP > Mirex > Dec 602 and Dec 604 > Dec 603 > CP in suspended sediments and sediment cores, whereas Mirex was highest in lake trout, followed by Dec 602 and DP. Dec 602 concentrations were 50 to 380 times greater than those of DP in lake trout, indicating Dec 602 has a greater bioaccumulation potential. The estimated biota-sediment accumulation factor (BSAF) for Dec 602 was much greater than for DP in Lake Ontario, and was greater than those calculated for PBDEs, indicating that assessment of some dechlorane compounds is merited if use is ongoing or planned.