AS1: Effects of POPs and Hg on Arctic wildlife: AMAP assessment

Date: Thursday October 11, 2018

Location: Valtuustosali, City Hall

Time: 8:30-10:00

Since the last assessments addressing biological effects of persistent organic pollutants (POPs) (2009) and mercury (2011), a number of new studies have been published in the scientific literature on (potential) biological effects of these contaminants. Organohalogen compounds (OHCs) and mercury have received particular attention, and in some studies this work is being combined with assessment of climate change impacts. New chemical contaminants are being detected in the Arctic, but as yet little information is available on the potential biological and ecosystem effects of these chemicals of emerging Arctic concern (CEAC). This special session would focus on the results of the new AMAP assessment that addresses some of these issues and provides an overview of the current state of knowledge (reviewing scientific work conducted 2010 to present). It covers levels of OHCs and Hg and/or associated effects in key Arctic marine and terrestrial mammals, birds and fish species and populations. It also addresses the current knowledge on how combined effects of several OHCs, (including perfluoroalkyl substances, PFASs) and Hg, as well as several individual or congener-specific contaminants, can affect biological pathways and outcomes. Furthermore, consideration will be given to potential toxic effects of combined exposure to both targeted and as yet unknown contaminants of emerging concern, and how this advances our understanding of impacts of complex contaminant mixtures that reflect environmentally realistic exposure scenarios for Arctic biota. Depending on the species and population, and tissue and contaminant burdens, exposure levels can be great enough to exceed putative risk-threshold levels that have been previously estimated for non-target species and species outside the Arctic. In new Arctic monitoring work, species exposure to specific OHCs (such as PCBs) and Hg have been shown to result in deleterious and observable effects via mode(s) of action and mechanisms that are a function of the contaminant type and level of exposure. The assessment therefore includes an updated risk assessment for sum PCBs and Hg for a number of Arctic species.

Chairs: Robert Letcher, Environment and Climate Change Canada; Rune Dietz, Aarhus University

Format: Series of presentations followed by discussion

Presentations:

  1. Biological effects of contaminant exposure in Arctic wildlife and fish: Christian Sonne, Aarhus University pdf
  2. Risk evaluation of PCBs and Hg in marine and terrestrial mammals and birds: Rune Dietz, Aarhus University  pdf
  3. Contaminant exposure, pathways and effects in a changing Arctic: Igor Eulaers, Aarhus University  pdf
  4. Key findings, conclusions, recommendations and the future directions for understanding POP and mercury impacts in Arctic wildlife and fish: Robert Letcher, Environment and Climate Change Canada  pdf


Abstracts:

Biological effects of contaminant exposure in Arctic wildlife and fish

Christian Sonne, Rob Letcher, Jean Pierre Desforges Igor Eulaers and Rune Dietz

The relationship between contaminant exposure (PCB and Hg) and physiological and pathological endpoints has been divided into mammals, birds and fish. Endpoints included thyroid hormones (TH) and steroid hormones (SH) in blood, vitamins in blood and tissues, histopathology, reproduction, immune toxicity, blood biochemistry, CYP-450, oxidative stress and genotoxicity. CYP450 increase with POP concentrations across all studies. Opposite to this, concentrations of hormones and vitamins generally showed negative associations with POPs though this varied depending on species and tissue/matrix. The immune system is also negatively affected across species, which includes both the humoral and cellular systems as supported by In vitro studies and modelling. Recently, novel biomarkers of ROS and genotoxicity have also been employed in a few species of mammals and birds. Histopathological changes occur in liver, kidney and thyroid glands and seem to be affected negatively by POPs and Hg concentrations and the same goes for BMD. New studies of polar bear brains show that steroid hormones are positively correlated with PFAS while neurochemicals was negative correlated with the same PFAS compounds. Polar bears, pilot whales, beluga and glaucous gulls are the four species analysed for a broader number of biomarkers. Across these species, thyroid hormones generally decreased while vitamin A and E increased in liver and decreased in blood. The concentrations of steroid hormones did not show a clear association with POPs, however, there is a tendency for testosterone to be negatively correlated to PCBs. Of recently applied biomarkers, genotoxicity has been shown for polar bears and for a few birds and fish spp. mainly driven by PCBs. Compared to previous AMAP Assessments, this update showed higher consitency among studies and overlap of enpoints and create hope for a future assessment focusing on effects on the population level.

 

Risk evaluation of PCBs and Hg in marine and terrestrial mammals and birds

Rune Dietz, Rob Letcher, Jean Pierre Desforges Igor Eulaers and Christian Sonne

In this AMAP assessment we provide an update on the current knowledge, i.e. 2010 to present, of the levels of OHCs and Hg and/or associated effects in key Arctic marine and terrestrial mammal, bird and fish species and populations. Based on PCB concentrations as being the dominant effect contributor, and an intermediate conservative critical body residue for PCBs of 10 µg/g l.w., risk quotients (RQ) were calculated and reported for the entire Arctic region and bordering waters. Based on the RQ geographical pattern, killer whales were found to be the highest exposed species, with four out of five groups having RQs above 1, which was true for transient Pacific killer whales as well. Population effect modelling has shown PCB-mediated effects on reproduction and immunity having severe consequences for the long-term population viability in 1/10 of the 4/20 Arctic/World wide killer whale populations with measured PCB tissue burdens. Long-finned pilot whale from the Faroe Islands, also had large group proportions with RQs above 1. Beluga populations however, all seem to have RQs below 1 indicating this species is not facing major problems with their immune or hormone systems. Similar to belugas, all ringed seals were below 10 µg/g lw leading to RQs below 1 and indicated this arctic species is not likely having their immune and hormonal systems detrimentally affected by PCB exposure. White-tailed sea eagle, gyrfalcon and peregrine falcon had high RQs above 1 in 71-85% of the birds. It should be highlighted that the present risk evaluation is built on uncertain critical body residues that may change between species and populations. There is limited work on species-relevant health surveys including dose response studies on live cells as well as limited work done on population effect modelling. A trans-Arctic effects assessment was conducted for total mercury (tHg) after year 2000. In general, most marine mammal species are at no or low risk for tHg exposure mediated health effects. However, for some high trophic species, such as polar bears, certain toothed whales including pilot whales, adult killer whales, narwhals and belugas, as well as hooded seals, a part of the population is at high or severe risk. Polar bears from the central-high Canadian and U.S. high Arctic, as well as pilot whales from the Faroe Islands, carried hepatic tHg burdens of the greatest concern. Bird mercury concentrations were above toxicity benchmarks in many areas throughout the marine environment, particularly for northern fulmar, double-crested cormorant and pigeon guillemot, as well as freshwater and terrestrial species in the Alaskan environment including northern shoveler, common loon, peregrine falcon, red-throated loon, pacific loon, bald eagle, green-winged teal and yellow-billed loon. In the North Atlantic, only a small proportion of unhatched chicks of black guillemot were at high risk. As expected, terrestrial mammals, with the exception of Arctic foxes on Iceland, which showed low to moderate risk, did not show risk for Hg intoxication, based on the limited recent Hg data available.

 

Contaminant exposure, pathways and effects in a changing Arctic

Igor Eulaers, Rob Letcher, Jean Pierre Desforges, Christian Sonne and Rune Dietz

The Arctic ecosystem and its wildlife has not only been an environmental sink for major long-range transported industrial chemicals, such as persistent organic pollutants (POPs) and Mercury (Hg), but has been subject to rapid environmental change. Ongoing change is not only exhibited through changing sea ice and glacier dynamics as well as ocean and atmospheric currents but is also manifested in changing food web composition and dynamics, and the interactions of biota with their abiotic environment. Such change is believed to have a pronounced impact on the composition and intensity of contaminant cocktails, their abiotic and biotic long-range versus local origin and pathways, bioavailability to and biomagnification through the food web, and ultimately effects in Arctic wildlife. We will present a state-of-the art overview of the available knowledge on changing biotic and abiotic sources and pathways of Hg and POPs in the Arctic and how this growing proof of evidence can be taken into account in the assessment of contaminant exposure and effects in Arctic wildlife, Humans and ecosystems.

Key findings, conclusions, recommendations and the future directions for understanding POP and mercury impacts in Arctic wildlife and fish

Robert Letcher, Rune Dietz, Jean-Pierre Desforges Igor Eulaers and Christian Sonne

The previous presentations have outlined in more detail and depth the updates since 2010 of accumulated knowledge in the scientific literature on the exposure and/or (potential) biological effects of organohalogen POPs and mercury in Arctic wildlife and fish. A summary of the key findings, conclusions, and recommendations and the future directions are presently detailed. Major examples of key findings and knowledge gaps include that as of 2017 there continues to be a lack of data for POP and mercury exposure and biological effects in wildlife and fish from Arctic Russia, Fennoscandia and Alaska. Depending on the species/population/tissue contaminant burdens, exposure levels in key Arctic biota (marine and terrestrial mammals, birds and fish) can exceed putative risk threshold levels estimated for non-target species and species from outside the Arctic. Based on PCB concentrations (as the dominant effect contributor for reproductive, immune and/or carcinogenic effects) and a conservative critical body residue for PCBs of 10 µg/g lw, risk quotients (RQ) were calculated and reported for the entire Arctic region and bordering waters. RQs make it possible to summarize the cumulative effects of environmental contaminant mixtures for which critical body burdens can be estimated. Understanding and predicting the biological effects of complex contaminant mixtures within a multi-stressor framework remains one of the great challenges of Arctic ecotoxicology. There is a need to establish concentration thresholds for biologically relevant health effects in wildlife and fish. Effects need to be assessed in relation to spatial and temporal variation in dietary pathways of exposure. Assessing the combined effects of contaminant exposure with natural stressors is required, i.e. infectious and zoonotic diseases. The OneHealth concept should be explored in future assessment integrating information from both wildlife and human health studies.

 

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