Relationship between persistent halogenated organic contaminants and TCDD-toxic equivalents on EROD activity and retinoid and thyroid hormone status in northern fulmars

Mercury contamination and potential health risks to Arctic seabirds and shorebirds

Since the last Arctic Monitoring and Assessment Programme (AMAP) effort to review biological effects of mercury (Hg) on Arctic biota in 2011 and 2018, there has been a considerable number of new Arctic bird studies. This review article provides contemporary Hg exposure and potential health risk for 36 Arctic seabird and shorebird species, representing a larger portion of the Arctic than during previous AMAP assessments now also including parts of the Russian Arctic. To assess risk to birds, we used Hg toxicity benchmarks established for blood and converted to egg, liver, and feather tissues. Several Arctic seabird populations showed Hg concentrations that exceeded toxicity benchmarks, with 50 % of individual birds exceeding the "no adverse health effect" level. In particular, 5 % of all studied birds were considered to be at moderate or higher risk to Hg toxicity. However, most seabirds (95 %) were generally at lower risk to Hg toxicity. The highest Hg contamination was observed in seabirds breeding in the western Atlantic and Pacific Oceans. Most Arctic shorebirds exhibited low Hg concentrations, with approximately 45 % of individuals categorized at no risk, 2.5 % at high risk category, and no individual at severe risk. Although the majority Arctic-breeding seabirds and shorebirds appeared at lower risk to Hg toxicity, recent studies have reported deleterious effects of Hg on some pituitary hormones, genotoxicity, and reproductive performance. Adult survival appeared unaffected by Hg exposure, although long-term banding studies incorporating Hg are still limited. Although Hg contamination across the Arctic is considered low for most bird species, Hg in combination with other stressors, including other contaminants, diseases, parasites, and climate change, may still cause adverse effects. Future investigations on the global impact of Hg on Arctic birds should be conducted within a multi-stressor framework. This information helps to address Article 22 (Effectiveness Evaluation) of the Minamata Convention on Mercury as a global pollutant.

Flame retardants and their associations with thyroid hormone-related variables in northern fulmars from the Faroe Islands

Flame retardants (FRs) are widely reported in tissues of seabirds including birds sampled from remote areas. There is evidence that FRs can disrupt the hypothalamic-pituitary-thyroid (HPT) axis in seabirds, although information is limited on thyroid-related mechanisms and effects. This study investigated the associations between concentrations of polybrominated diphenyl ethers (PBDEs) and other FRs, and changes in the HPT axis in northern fulmars (Fulmarus glacialis) from the Faroe Islands (North Atlantic). Plasma concentrations of thyroid hormones (THs), hepatic deiodinase type 1 (D1) activity, and transcription of selected TH-related genes in liver were used as markers of HPT axis changes. Liver concentrations of a certain PBDE congeners and other FRs including pentabromoethylbenzene (PBEB), dechlorane 602 (Dec-602), and dechlorane plus (DP) were associated with changes in thyroid status. Specifically, liver PBDE, PBEB and Dec-602 concentrations were associated with plasma TH levels (free thyroxine [FT₄] and total triiodothyronine [TT₃]). Liver DP concentrations were positively correlated with the TT₄:FT₄ ratios and mRNA levels of UDP-glucuronyltransferase-1, while those of PBEB were negatively associated with TT₄:TT₃ ratios and D1 activity. D1 activity was also positively associated with the tri-, tetra- and hexa-BDE congeners. Moreover, transcription of ABCC2, a hepatic TH transporter, was associated with certain liver PBDE concentrations. Although PBDEs and other FRs may be potential inhibitors of D1 activity, only a few of the targeted FRs had modest associations with hepatic D1 activity. Regardless, the relationships reported herein indicated that exposure to moderate levels of FRs can be associated with thyroid axis perturbation at the molecular/biochemical levels in this North Atlantic seabird species.

Tracking pan-continental trends in environmental contamination using sentinel raptors-what types of samples should we use?

Biomonitoring using birds of prey as sentinel species has been mooted as a way to evaluate the success of European Union directives that are designed to protect people and the environment across Europe from industrial contaminants and pesticides. No such pan-European evaluation currently exists. Coordination of such large scale monitoring would require harmonisation across multiple countries of the types of samples collected and analysed-matrices vary in the ease with which they can be collected and the information they provide. We report the first ever pan-European assessment of which raptor samples are collected across Europe and review their suitability for biomonitoring. Currently, some 182 monitoring programmes across 33 European countries collect a variety of raptor samples, and we discuss the relative merits of each for monitoring current priority and emerging compounds. Of the matrices collected, blood and liver are used most extensively for quantifying trends in recent and longer-term contaminant exposure, respectively. These matrices are potentially the most effective for pan-European biomonitoring but are not so widely and frequently collected as others. We found that failed eggs and feathers are the most widely collected samples. Because of this ubiquity, they may provide the best opportunities for widescale biomonitoring, although neither is suitable for all compounds. We advocate piloting pan-European monitoring of selected priority compounds using these matrices and developing read-across approaches to accommodate any effects that trophic pathway and species differences in accumulation may have on our ability to track environmental trends in contaminants.

Short-term fasts increase levels of halogenated flame retardants in tissues of a wild incubating bird

Many species are adapted for fasting during parts of their life cycle. For species undergoing extreme fasts, lipid stores are mobilized and accumulated contaminants can be released to exert toxicological effects. However, it is unknown if short-term fasting events may have a similar effect. The objective of this study was to determine if short successive fasts are related to contaminant levels in liver and plasma of birds. In ring-billed gulls (Larus delawarensis), both members of the pair alternate between incubating the nest for several hours (during which they fast) and foraging, making them a useful model for examining this question. Birds were equipped with miniature data loggers recording time and GPS position for two days to determine the proportion and duration of time birds spent in these two activities. Liver and plasma samples were collected, and halogenated flame retardants (HFRs) (PBDEs and dechlorane plus) and organochlorines (OCs) (PCBs, DDTs, and chlordane-related compounds) were determined. Most birds (79%) exhibited plasma lipid content below 1%, indicating a likely fasted state, and plasma lipid percent declined with the number of hours spent at the nest site. The more time birds spent at their nest site, the higher were their plasma and liver concentrations of HFRs. However, body condition indices were unrelated to either the amount of time birds fasted at the nest site or contaminant levels, suggesting that lipid mobilization might not have been severe enough to affect overall body condition of birds and to explain the relationship between fasting and HFR concentrations. A similar relationship between fasting and OC levels was not observed, suggesting that different factors are affecting short-term temporal variations in concentrations of these two classes of contaminants. This study demonstrates that short fasts can be related to increased internal contaminant exposure in birds and that this may be a confounding factor in research and monitoring involving tissue concentrations of HFRs in wild birds.

Effect of tocopherol and acetylsalicylic acid on the biochemical indices of blood in dioxin-exposed rats

New sources of dioxins and increased dioxin concentrations in the environment, coupled with their increased bioavailability along the food chain and accumulation in adipose tissues, contribute to various adverse long-term biological effects. The purpose of the study was to determine whether tocopherol protects the CNS by decreasing the pro-inflammatory influence of free radicals generated by TCDD; whether acetylsalicylic acid inhibits the production of inflammatory mediators; and whether the combined administration of tocopherol and acetylsalicylic acid to TCDD-exposed rats has a potential CNS-protective effect. The study included 117 rats divided into 8 groups: 75 female and 12 male Buffalo rats aged 8-10 weeks, weighing 140-160 g; as well as 30 female rats aged 6 weeks and weighing 120 g, which were the offspring of females from each study group. In the experiment, the following substances were used: 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), dosed at 5 μg/kg BW and 12.5 μg/kg BW, diluted in a 1% DMSO solution at the concentration of 1 μg/ml; α-tocopherol acetate, dosed at 30 mg/kg BW, in 0.2 ml of oil solution; and acetylsalicylic acid, 50mg/kg BW, suspended in 0.5 ml of starch solution, administered orally using a feeding tube. Pleurisy was induced by an injection of 0.15 ml of 1% carrageenin solution. The use of tocopherol reduces the adverse effects of the inflammatory reaction induced by TCDD. Administering tocopherol improves protein metabolism by reducing protein catabolism, and raises γ-globulin fraction levels. Combined acetylsalicylic acid and tocopherol suppress catabolic processes accompanying inflammation.

Contrasting retinoid and thyroid hormone status in differentially-contaminated northern fulmar colonies from the Canadian Arctic, Svalbard and the Faroe Islands

The northern fulmar (Fulmarus glacialis) has previously been shown to accumulate a wide range, and occasionally high concentrations of organochlorines (OCs) (e.g., PCBs, chlorobenzenes, DDT- and chlordane-related compounds, dioxins and furans). The present study aimed to investigate, using a meta-analysis approach, the variations in cytochrome P450 (CYP) 1A-like enzyme induction based on ethoxyresorufin O-deethylase activity (EROD) and selected physiological variables (retinoids and thyroid hormones) in northern fulmar breeding in three differentially OC-exposed populations: Nunavut (Canadian Arctic), Svalbard (Norwegian Arctic) and the Faroe Islands. Substantially higher (roughly two-fold) OC levels were uncovered in the liver of this long-lived fulmarine petrel breeding in the Faroe Islands relative to Svalbard and Nunavut. Liver levels of PCDDs, PCDFs and non-ortho PCBs in Faroe Islands fulmars were amongst the highest reported thus far in any seabirds from the northern regions. Positive correlations were depicted in combined fulmars (all three populations) between hepatic EROD activity and concentrations of OCs, in which strongest associations were found for dioxin-like compound (PCDFs and PCDDs) and TEQ concentrations. Moreover, moderate to strong positive correlations were found between liver OC concentrations and plasma total thyroxin (TT(4)) levels and TT(4)/total triiodothyronine (TT(3)) level ratios, as well as strong negative correlations between the same suite of OCs and plasma TT(3) levels. Hepatic OC concentrations (PCBs, PCDDs, PCDFs, HCB, p,p'-DDE and oxychlordane) also were positively correlated with hepatic retinyl palmitate levels which, in turn, were associated with a significant decrease in plasma retinol levels and somewhat unchanged liver retinol levels. The present meta-analysis investigation on northern fulmar breeding in three geographically-distant sites illustrated that OC exposure (mainly PCBs and dioxins/furans) may be associated with modulation of the thyroid and retinoid homeostasis. However, the impact of confounding environmental factors (e.g., temperature and nutritional status) on current physiological variable variations could not be ruled out, and thus any cause-effect linkages between thyroid and retinoid system perturbation and OC exposure cannot be ascertained.

Halogenated organic contaminants and their correlations with circulating thyroid hormones in developing Arctic seabirds

Thyroid hormones are essential for normal growth and development and disruption of thyroid homeostasis can be critical to young developing individuals. The aim of the present study was to assess plasma concentrations of halogenated organic contaminants (HOCs) in chicks of two seabird species and to investigate possible correlations of HOCs with circulating thyroid hormone (TH) concentrations. Plasma from black-legged kittiwake (Rissa tridactyla) and northern fulmar (Fulmarus glacialis) chicks were sampled in Kongsfjorden, Svalbard in 2006. The samples were analyzed for thyroid hormones and a wide range of HOCs (polychlorinated biphenyls (PCBs), hydroxylated (OH-) and methylsulphoned (MeSO-) PCB metabolites, organochlorine pesticides (OCPs), brominated flame retardants (BFRs), and perfluorinated compounds (PFCs)). Concentrations of HOCs were generally low in kittiwake and fulmar chicks compared to previous reports. HOC concentrations were five times higher in fulmar chicks compared to in kittiwake chicks. PFCs dominated the summed HOCs concentrations in both species (77% in kittiwakes and 69% in fulmars). Positive associations between total thyroxin (TT4) and PFCs (PFHpS, PFOS, PFNA) were found in both species. Although correlations do not implicate causal relationships per se, the correlations are of concern as disruption of TH homeostasis may cause developmental effects in young birds.

Biomarker responses associated with halogenated organic contaminants in northern fulmars (Fulmarus glacialis) breeding in the Canadian Arctic

We examined relationships between hepatic concentrations of halogenated organic contaminants and ethoxyresorufin O-deethylase (EROD) activity and retinoid (vitamin A) concentrations in livers, as well as retinol and thyroid hormone (TT(3), TT(4)) levels in blood plasma, of northern fulmars at two breeding colonies in the Canadian High Arctic. Biomarker levels or responses did not differ significantly between males and females at either colony, nor was there any significant difference between colonies. No significant relationships were found between thyroid hormone or hepatic retinoid concentrations and any of the dioxin-like compounds or their Toxic Equivalents (TEQs) although significant positive correlations were found with plasma retinol (p < 0.03). EROD activity was significantly correlated with hepatic dioxin-like compounds and their TEQs (p < 0.001) as well as total PCBs (p < 0.01), which suggests that EROD induction occurs in northern fulmars at environmentally-relevant concentrations.

EROD activity in peripheral blood lymphocytes and 1-hydroxypyrene in urine and milk as biomarkers of PAH exposure in dairy ruminants

Presently, few biomarker-based approaches are available for the evaluation of environmental exposure to persistent organic pollutants in dairy ruminants. In this study, goats (Capra hircus) were orally administered a mixture of pyrene, phenanthrene, and benzo[a]pyrene daily over a 40-d period (1 or 50 mg/d). Milk and urine 1-hydroxypyrene levels, ethoxyresorufin-O-deethylase (EROD) activity in peripheral blood lymphocytes (PBL) as well as urinary levels of 2- and 3-hydroxyphenanthrene were determined at 10-d intervals. 1-Hydroxypyrene excretion in milk and urine significantly increased and then achieved a plateau at 10 d. Transfer rates of 1-hydroxypyrene were calculated to be approximately 0.5 and 25% in milk and urine, respectively. Concentrations in milk and urine were proportional to the ingested doses. These results demonstrate that 1-hydroxypyrene in milk or urine may be used as a biomarker for evaluating the exposure of dairy ruminants to polycyclic aromatic hydrocarbons (PAHs) over an extended exposure period. Constitutive EROD activity in lymphocytes was 0.5 ± 0.3 pmol resorufin/min/mg protein, and was significantly induced over the entire exposure time, before stabilizing after 40 d at 6.30 ± 1.3 and 18.89 ± 1.12 pmol resorufin/min/mg protein for 1 mg/d and 50 mg/d doses, respectively. Induction kinetics were calculated using a logistic-like model and approximate dose-response curves were designed. We therefore propose EROD activity in PBL as a relevant, convenient, and noninvasive biomarker of subchronic exposure of dairy ruminants to CYP450 inducing PAH.