Canadian Arctic Contaminants Assessment Report III (2013): Persistent Organic Pollutants in Canada's North
1. The context of this assessment
The Northern Contaminants Program (NCP) was established in 1991 in response to concerns about human exposure to elevated levels of contaminants in wildlife species that are important to the traditional diets of northern Aboriginal peoples. This is the third assessment of persistent organic pollutants (POPs) conducted by the NCP and the first that focusses solely on POPs. It is a companion document to a Highlights report and the Mercury assessment, as well as an earlier Human Health assessment. Previous assessments in 1997 and 2003 summarized results of Phase 1 (1991-1996) and Phase II (1997-2002) of the NCP and included both heavy metals and POPs. Under Phase III of the program which began in 2003-04, environmental monitoring focussed on fewer sampling sites for both air and biological samples (Table 1). The biological sampling programs were redesigned with the goal of being able to detect a 10% annual change in contaminant concentration over a period of 10-15 years with a power of 80% and confidence level of 95%. This involved moving to annual sampling for key species (beluga, ringed seals, seabirds, arctic char) and, for beluga and ringed seals, a reduction in the number of locations sampled. Starting in 2009, analysis of high volume air sample extracts from Alert was reduced to one sample every month with the remaining sample extracts archived and temporal trends for ringed seals, arctic char and beluga were limited to two or three major sites per species.
|Air - hi volume||Alert||1992–2010||7 day continuous|
|Air - passives||Up to 7 arctic/sub-arctic locations||2005–2011||Quarterly|
|Arctic char (sea-run)||Cambridge Bay, Pond Inlet , Nain||2004–2011||Annual|
|Arctic char (landlocked)||Lakes Resolute, Char, Amituk and Hazen||2004–2011||Annual|
|Burbot||Fort Good Hope, Great Slave Lake West Basin and East Arm||2004–2011||Annual|
|Lake trout||Lake Laberge, Kusawa Lake, Great Slave Lake West Basin and East Arm||2004–2011||Annual|
|Caribou||Northern Yukon and Southwestern Nunavut (Porcupine, Qamanirjuaq herds)||2006, 2008||Single study|
|Ringed seals||Arviat, Resolute, Sachs Harbour and other locations to 2009||2004–2011||Annual|
|Beluga||South Beaufort, Cumberland Sound||2004–2011||Annual|
|Polar bears||West Hudson Bay and other locations||2004–2011||Annual|
|Seabirds (thick billed murre, blacklegged kittiwakes||Prince Leopold Island, Coats Island||2004–2011||Annual|
1All programs include data from earlier years based on existing data or reanalysis of archived samples
In addition to the enhanced long-term monitoring program, the NCP continued to fund research into pathways, processes and biological effects of POPs in the Canadian Arctic. This included modeling of long range atmospheric and oceanic transport, assessment of bioaccumulation and biomagnification in arctic food-webs, studies on the potential impact of climate change on POPs in the Arctic, and a comprehensive study of biological effects in beluga whales.
This assessment covers results on POPs in the Canadian Arctic over the period of 2003 to 2011. It draws on results from Phase III of the NCP (2003-2011) as well as on any other published or unpublished studies up to early 2013. This 8 to 9 year reporting period has seen much new knowledge developed on temporal trends of POPs in air and biota, new POPs in many environmental compartments, and on ocean transport to the Arctic. The possible influence of climate warming on trends of POPs has also been investigated.
2. NCP Science to Policy Actions
The period of scientific developments covered by this assessment was also highly significant for global regulatory action on POPs. Most notably, the Stockholm Convention on POPs entered into force in 2004 introducing global regulations aimed at eliminating, or severely curtailing, emissions of the so-called “dirty dozen” POPs. The development of the Stockholm Convention is regarded as a major achievement for the NCP which, along with Arctic Council’s Arctic Monitoring and Assessment Programme (AMAP), provided much of the foundational science upon which the Convention is based. This assessment documents declining levels of many of the dirty dozen POPs, also referred to as legacy POPs, and also presents data on many of the so-called new POPs, 10 of which have been added to the Stockholm Convention since 2004. Data and information from the NCP contributed to the addition of these new POPs and will continue to play a critical role in the assessment of future new POPs. The NCP will also be providing updated information from this assessment to the 2015 second report of the Global Monitoring Plan established under Article 16 of the Stockholm Convention. The ongoing active participation of the NCP on national and international initiatives related to the assessment and regulation of POPs will ensure that NCP science continues to have a significant influence on policies to protect ecosystem and human health in Canada’s North. The following scientific recommendations have been developed based on NCP’s continuing role to provide scientific input to domestic and international regulatory initiatives, and to better inform policy development at national and international levels.
- There is a need for continued monitoring of POPs in the Arctic in order to ensure that the Stockholm Convention is effective at reducing levels of these pollutants in the environment. There is also a need for ongoing surveillance of emerging chemical contaminants, whose detection in the Arctic environment provides strong evidence for having them added to the Stockholm Convention as new POPs.
- In order to improve the regulation of POPs, domestic and international regulatory agencies require a better understanding of how POPs behave in the environment and the effects that they have on ecosystems and human health. As recommended by this assessment and echoed by international organizations such as UNEP and AMAP, a better understanding of how climate change will influence POPs is also needed. Predicting the impacts climate change will have on POPs will be critical to future development of POPs regulations and evaluating the effectiveness of these regulations.
3. Information on the chemicals of interest has expanded
The list of individual compounds analysed was expanded in Phase III particularly for perfluorinated and polyfluorinated alkyl substances (PFASs), brominated flame retardants (BFRs) and current use pesticides (CUPs). About 35 chemicals or chemical groups that were not previously reported, or for which only very limited measurements were available in the previous assessment, have been detected particularly in arctic air, snow and biota (Table 2). See the Glossary for more details on the chemical names and abbreviations.
|Major groups of POPs and other persistent organics||NCP I (1991-1996)||NCP II (1997-2002)||NCP III (2003-2011)|
|PCBs1||Air, snow, sediment, seawater, biota||Air, seawater, sediment, biota||Air, snow, seawater, biota|
|OC pesticides2||Air, snow, sediment, seawater, biota||Air, seawater, sediment, biota||Air, snow, biota|
|Chlorobenzenes||Air, snow, sediment, seawater, biota||Air, seawater, sediment, biota||Air, snow, biota|
|Chlorinated dioxins/furans||Biota||Air, sediment, biota||Biota|
|Chlorinated naphthalenes (PCNs)||Air, biota||Air, biota|
|Chlorinated paraffins||Air, sediment, biota||Biota|
|Endosulfan||Air, seawater, biota||Air, seawater, biota|
|Polybrominated diphenyl ethers (PBDEs)||Sediment, biota||Air, snow, seawater, sediment, biota|
|Hexabromocyclododecane (HBCDD)||Air, snow, seawater, biota|
|Other Brominated and chlorinated flame retardants||Air, snow, seawater, biota|
|Penta and hexabromobiphenyls||Air, biota|
|Current use pesticides3||Air, snow, seawater, lake water, biota|
|Perfluorooctane sulfonate (PFOS) and other perfluoro-alkyl acids and alcohols||Air, snow, seawater, lake water, sediment, biota|
1various congeners depending on the study; 2DDTs, hexachlorocyclohexanes (HCHs), chlordanes, toxaphene; 3Current use pesticides including dacthal, chlorothalonil, chlorpyrifos, pentachloronitrobenzene(PCNB), trifluralin
Among the chlorinated organics, PCNs are now more widely measured (air, seals, beluga, seabirds). Only limited new data were available for chlorinated paraffins over the period 2003-2011 due to analytical difficulties for the labs involved with measurement. Both the PCNs and short chain chlorinated paraffins SCCPs) are currently being evaluated for inclusion in the Stockholm Convention.
New groups of chemicals measured in the past 10 years included CUPs such as dacthal, PCNB, trifluralin and chlorthalonil which became routinely reported for air and seawater. Limited measurements of CUPs were also made in marine and terrestrial food webs which indicated that these CUPs do not biomagnify. About 20 brominated and chlorinated flame retardant chemicals also were included in analytical suites. Many were also being assessed under Canada’s Chemical Management Plan. For HBCDD, the most widely detected non-PBDE flame retardant, the data for HBCDD in Canadian arctic biota formed an important part of the risk profile adopted by the Stockholm Convention in 2010. However most of the other non-PBDE BFRs have been below detection limits in air and biological samples.
The discovery of PFASs in arctic wildlife, and subsequently in all environmental compartments, is perhaps the most surprising result of the past 10 years of arctic contaminants monitoring. Unlike chlorinated and brominated POPs, these chemicals are relatively water soluble and “oleophobic”, accumulating in protein rich tissues such as liver and blood. The precursors of PFOS and other PFASs are highly volatile and best measured in the atmosphere. However they can be degraded in the atmosphere to persistent and bioaccumulative substances. The presence of high levels of PFOS and long chain perfluorocarboxylates (PFCAs) in Arctic marine mammals and polar bears also illustrated the need to examine a broader array of chemicals for their ability to be transported to the Arctic, to be transformed to persistent substances, and to accumulate in arctic food webs.
The use of passive air samplers began under Phase III and results for Arctic locations from this program, which was part of the Global Atmospheric Passive Sampling (GAPS) program were comparable with the active high volume sampling at Alert. Passive air samplers are advantageous because of their low cost, simple construction and electricity-free operation. Modification of the absorbent in the samplers enabled sampling of volatile precursors of PFOS and PFCAs as well as volatile methyl siloxanes in Arctic air and comparisons with rural and urban areas around the globe. However, low air concentrations in the Arctic often result in detectability issues. A newly developed flow-through passive sampler, which has shown comparable results at a much lower cost and maintenance than high-volume air sampling at Alert may resolve this issue.
The importance of particle transport of non-volatile contaminants such as the widely used flame retardant decaBDE has been demonstrated by the detection of elevated concentrations in the Devon Island ice cap. This transport pathway was previously recognized mainly for inorganic chemicals such as lead or sulfate. Other “new” flame retardant chemicals in air samples taken at Alert are also mainly on particles. BFRs such as bis(tribromophenoxy) ethane,, ethylhexyl-tetrabromobenzoate and bis(ethylhexyl)tetrabromophthalte were generally detected with concentrations similar to those of the dominant PBDE congeners.
Several independent studies that have screened chemicals in commerce have demonstrated there are hundreds of substances with properties similar to those of known persistent organic chemicals detected in the Arctic. These may be future candidates for monitoring in Arctic air and wildlife. To model the transport of these candidate chemicals to the Arctic requires information on quantities of chemicals used and emitted in source regions. This information is generally not available except for CUPs. However, modeling of long range atmospheric transport of POPs has advanced to the point that it is possible to use a global model to suggest a cap on the annual emissions in various parts of the world, depending on the efficiency of transport to a vulnerable area.
The detection of perfluorinated alkyl acids such as PFOS and PFOA in arctic seawater, along with global modeling, has demonstrated the importance of ocean transport of contaminants. The slow movement and large mass of seawater also underlines the very long term nature of the exposure of arctic marine food chains to contaminants. The discovery of the PFASs in seawater has led to a tremendous expansion of modelling of long range ocean transport (LROT) transport of PFASs and other POPs to the Arctic. Environmental measurements of two major PFASs, PFOS and PFOA are in reasonable agreement with currently available data for ocean waters suggesting that available emission estimates for these two compounds are plausible. Modelling results suggest that redistribution of these contaminants from lower latitudes to the Arctic Ocean is ongoing and the total mass (and average concentration) of PFOA and PFOS in the marine environment is expected to increase for the next 10 to 20 years. A major conclusion from LROT modelling is that exposure of marine food webs to more water soluble POPs in the eastern Arctic waters, may be substantially different than exposure elsewhere e.g. in the western Canadian arctic waters. This pattern of distribution is distinct from LRAT, which tends to result in more uniform deposition fluxes and therefore of concentrations/exposure in the water column. This is borne out by observations of different concentrations and rates of change of POPs in beluga and ringed seals from the southern Beaufort Sea compared to Hudson Bay and Cumberland Sound regions.
- Much further work is needed to assess whether climate change, particularly warming trends, is affecting POPs transport to the Arctic
- Urgent need for more research on other particle bound organic chemicals that may be entering the arctic environment.
- More data are required on the quantities of chemicals used and emitted in source regions.
- Monitoring programs need to consider including a broader range of chemicals, including both parents and transformation products, which may have POP-like properties to assess their potential for long-range transport as well as to assess changes by developing time trends in different media. Chemicals with potential for Arctic contamination can first be identified using fate and transport models.
- More focus is needed on new candidate chemicals on current Stockholm Convention and UNECE LRTAP lists (PCNs, pentachlorophenol, hexachlorobutadiene) as well as on SCCPs, chlordecone and hexabromobiphenyl in order to fully assess their importance as contaminants in the biological environment.
4. Knowledge of time trends of POPs has greatly improved
Temporal trends of POPs listed in the Stockholm Convention and other persistent organic chemicals are summarized In Table 3 by colour-coding (Green for declines; red for increases). Results for air monitoring indicate that many legacy POPs, including organochlorine (OC) pesticides and PCBs, are declining. Results for air sampled at Alert, on Northern Ellesmere Island, indicate that the rates of decline for the legacy POPs were generally more rapid in the period 1993 to 2001 compared to 2002 to 2009 (the most recent year reported). While overall trends (1993 -2009) for PCBs show a decline, the rates have slowed and some more highly chlorinated congeners have increased slightly in recent years. These increases may be associated with the increase in boreal forest fires that release previously deposited organic chemicals, such as PCBs. Changes associated with sea-ice cover and the cryosphere in general could also be a factor. Chlorinated pesticides such as hexachlorocyclohexanes (HCHs, particularly γ-HCH or lindane), DDT- and chlordane-related compounds (CHL) show more consistent declines over the period 1993 to 2009. Lindane was de-registered in Canada for use on canola seeds in July 2001 and a ban was introduced in 2004; air concentrations declined steadily as of 2001. Another widely used pesticide, endosulfan, showed steady concentrations in the period 1993 to 2001 but declining concentrations from 2006 to 2009 possibly reflecting reduced use in Canada, the USA, and Europe as this insecticide came under greater regulatory scrutiny.
Despite recent measurements of PFASs, time-series data for other POPs in seawater remain a major knowledge gap for Arctic contaminants. This information is crucial for understanding the fate and trends of contaminants and would be particularly useful for less bioaccumulative, more water soluble chemicals, such as current use pesticides. There is a need to clarify the relative importance of atmospheric and oceanic inputs as well as the relative importance of direct and precursor emissions to different remote ecosystems. Given the challenges for obtaining POPs data by large volume water sampling due to ship board contamination and infrequent cruises, consideration needs to be given to deploying passive samplers.
The statistical power of the temporal trend datasets for POPs in fish, seabirds and marine mammals has improved since the publication of CACAR II in 2003 and some datasets are capable of detecting a 5% change in concentration at a power of 80%. The main reason for the increased power is the introduction of annual sampling of key monitoring species beginning in 2004 which has increased the number of sampling years.
The declining trend in concentrations in biota is most apparent for OC pesticides and less evident for PCBs and chlorobenzenes (ΣCBz) (Table 3). In marine species, percent annual declines of ΣDDT ranged from 2.5%/year in thick-billed murre eggs (Lancaster Sound) to 11%/year in polar bear fat (western Hudson Bay, WHB). Declines of chlordane-related compounds (ΣCHL) ranged from 1.2%/year in murre eggs to 7.4%/year in blubber of ringed seals in Hudson Bay, while polar bears (WHB) showed no decline. Total HCHs (ΣHCH) declined in seals, beluga and polar bears due to rapid decline of the major isomer α-HCH (e.g. 12%/year in bears). However, β-HCH, the more bioaccumulative isomer, increased in the same species. This increase in β-HCH in seals varied regionally, with large increases in South Beaufort Sea seals (16% at Ulukhaktok) and a decline in Hudson Bay (2.5%/year). The case of β-HCH highlights the importance of ocean water moving through the Arctic archipelago from the Pacific Ocean via the Bering Sea and possibly Russian freshwater inputs. No other POP shows this trend although declines of PCBs, ΣDDT, ΣCHL were lower or non-existent in beluga, ringed seals and polar bears in the South Beaufort compared to Hudson Bay and East Baffin regions.
Declines of legacy POPs have generally been more rapid In freshwater fish than in marine animals. For example, PCBs in landlocked arctic char declined by 6.4% and 7.6%/year in Amituk Lake and Lake Hazen, respectively, versus 3.8% and 4.0%/year in thick-billed murres and northern fulmars, respectively. Declines of ≥ 5%/year were also seen for ΣHCH, ΣCHL, ΣDDT and toxaphene in lake trout from Lakes Laberge, Kusawa Lake and western basin of Great Slave Lake as well as in landlocked char in Lake Hazen, Char Lake and Amituk Lake. Declines for these OC pesticides were generally <5%/year in seabird eggs and marine mammals. A notable exception was the increase in concentrations of PCBs, ΣCHL, ΣDDTs, and toxaphene were over the period 2001 to 2009 in burbot liver sampled at Fort Good Hope on the Mackenzie River. However, as of 2010 concentrations of all four POPs had returned to levels found in the 1990s and early 2000s. PCBs and ΣCBz also increased in burbot and lake trout in Great Slave Lake in the period 2001–2005. These increases were not seen in lake trout in the Yukon (Lake Laberge and Kusawa Lake) or in landlocked char. Annual sampling made it possible to observe these changes. These temporary increases suggests some process that is influencing the availability of POPs in the Mackenzie basin. Climate warming has been suggested, however a general warming trend would not explain the increase followed by a decrease in concentrations. Nevertheless, shifts in the burbot and lake trout diet and feeding areas, which could also be induced by climate change, might change contaminant availability. Other possibilities include mobilization of legacy sources due to warming, e.g., increased erosion of river sediments.
New POPs such as PBDEs and PFOS generally increased in seals, seabirds, beluga, and polar bear samples from the 1990s until the early 2000s and are now declining. Retrospective analysis of collections from specimen banks enabled measurements of the PBDEs, PFASs and other contaminants in samples from the 1970s, ‘80s and ‘90s, and annual sampling as of early 2000s enabled relatively rapid declines to be observed. For example, ΣPBDEs achieved maximum concentrations in northern fulmar and thick-billed murre eggs in 2005 and 2006, respectively and declined to levels similar to those in the early 1990s within 3 years. Polar Bears, ringed seals and beluga appear to have achieved maximum ΣPBDEs in the period 2000-2004 in most locations. Similarly PFOS concentrations reached maxima in ringed seal livers in 1999-2003 in Hudson Bay, Lancaster Sound and East Baffin samples although in the southern Beaufort Sea animals concentrations continued to increase slowly (3.6%/year) to 2011.
A decline in PBDEs was also observed in air samples at Alert. PFOS precursors, MeFOSE and EtFOSE also declined while fluorotelomer alcohols (FTOHs) with 8 and 10-fluorinated carbon chains, increased over the period 2006-20010. The declines in PBDEs and PFOS in air and biota appear to be related to bans and voluntary phase outs of these substances in North America and Europe over the period 2001-2004. On the other hand some replacement chemicals such as hexabromocyclododecane (HBCDD) appear to be increasing. HBCDD was undetectable in biological samples from the 1990s and early 2000s but increased well above detection limits during 2005-2011 for burbot, lake trout, landlocked arctic char, and ringed seals. Maximum HBCDD was observed somewhat earlier (2003) in polar bears in WHB and beluga from southern Beaufort Sea. Data are too limited and levels to close to detection limits to assess whether other BFRs are increasing in air or biota.
Table 3. Overview of time trends of selected POPs and persistent organics in Canadian arctic air and biota . Estimated for all results from early 1990s to 2011
The table describes temporal trends for arctic air and wildlife (burbot, lake trout, landlocked char, seabirds, seals, beluga, and polar bears) monitored under the Northern Contaminants Program core monitoring program. The table illustrates how the monitoring program is now able to measure statistically significant decreasing trends for all persistent organic pollutants (POPs) originally included in the Stockholm Convention (PCBs, ∑CBz, ∑CHLs, ∑DDT, and toxaphene) in nearly all monitoring species and air. The table also shows statistically significant trends for newer POPs (∑PBDEs, HBCDD, PFOS and precursors, PFCAs and precursors), with some species and locations exhibiting increasing trends and others decreasing. Some species also show an increasing trend followed by a decreasing trend, particularly for newer POPs that were recently added to the Stockholm Convention. The table shows, with a few exceptions, how there is still insufficient data to measure trends of endosulfan, SCCPs, PCNs, and PCDD/Fs.
Reference: List of Acronyms
- PCBs – polychlorinated biphenyls
- ∑CBz – sum of chlorobenzenes
- ∑CHLs – sum of chlordane related compounds
- ∑DDT – sum of DDT related compounds
- ∑PBDEs – sum of polybrominated diphenyl ethers
- HBCDD - hexabromocyclododecane
- PFOS – perfluorooctane sulfonate
- PFCAs – perfluoroalkyl carboxylates
- SCCPs – short-chain chlorinated paraffins
- PCNs – polychlorinated naphthalenes
- PCDD/Fs – polychlorinated dibenzo-p-dioxins and furans
- Continued annual sampling is essential for detecting temporal trends of chemicals in commerce in biota. Annual sampling has been instrumental in demonstrating the rise and fall of new POPs, improving the statistical power of trends of legacy POPs, as well as in allowing investigations of the effect of climate change
- There are limited measurements and a lack of time trends of atmospheric POPs in the western and eastern Canadian Arctic. This data gap needs to be addressed either by use of hi-vol samplers or passive air samplers or some combination. Air monitoring seems particularly critical for the western Arctic given the known rise of organic chemical production and uses in Asia in the past decade
- Time-series data for POPs and new contaminants in seawater are needed for understanding the fate and trends of contaminants and would be particularly useful for the less bioaccumulative chemicals such as current use pesticides.
- While annual sample collection has boosted the statistical power of the biological program and therefore must be continued, consideration should be given to de-emphasizing annual measurements of some legacy POPs, where statistical analysis shows that the datasets meet monitoring goals, and placing more emphasis on new candidate or emerging chemicals which may have limited datasets.
- It must be recognized that a major strength of the temporal trend programs conducted under the NCP is the availability of archived samples from specimen banks. These must be maintained to continue to have a strong program for POPs monitoring.
5. Local sources may be important for new POPs
While the focus of this assessment is mainly on POPs entering the Canadian arctic via LRAT and LROT local sources of new POPs, as well as trends of legacy contaminants at contaminated sites, continued to be of interest. Measurements during the period 2003-2011 showed that PBDEs, PFOS and SCCPs were sources of local contamination in or near communities in the Canadian arctic. For example, a study of dumpsites in Iqaluit, Cambridge Bay and Yellowknife showed significantly higher ΣPBDE concentrations compared to corresponding background sites in these locations suggesting that PBDEs leach from the landfill. Short-chain and medium-chain chlorinated paraffins (MCCPs) levels were shown to be higher in sediments, water and fish samples collected in and around Iqaluit compared to a remote reference site. PFOS and related chemicals used in aqueous film forming foams (used to suppress fuel fires) were elevated in water and landlocked char from Merretta and Resolute Lakes, which are downstream of the Resolute Bay airport.
Monitoring in the marine and terrestrial environment at Saglek Bay (Nunatsiavut/Labrador) has shown that PCB concentrations in the surrounding environment (sediments, plants, deer mice, sculpin, and black guillemots) have decreased since the source of PCBs has been removed, and companion studies have shown that the decline in the PCB concentrations are associated with a decline in biological effects
The continued study of PCBs at Saglek Bay has improved the knowledge of the fate of sediment associated contaminants in nearshore Arctic marine environments and particularly on their transport to offshore depositional areas.
- Better knowledge of local contamination sources is needed for the interpretation of spatial and temporal trends particularly of new POPs which are in consumer products and therefore found in homes and dumpsites in all arctic communities
6. Knowledge of factors influencing levels and trends of POPs has improved
Over the period 2003-2011, significant progress was made in bioaccumulation modelling of POPs in both terrestrial and marine food webs. These modelling studies provided insights into understanding of pathways and processes influencing the accumulation of POPs in wildlife and humans and also the properties of chemicals that would likely biomagnify. Studies of the lichen-caribou-wolf food web showed that a wider range of chlorinated organics may biomagnify in terrestrial compared to marine food webs. This was explained by the presence of two air-breathing species in the food web and the fact that some chemicals with high octanol-air partition coefficients are eliminated less efficiently in air via the lungs than in water over the gill, resulting in their higher net uptake and retention in terrestrial top predators. Biomagnification of PFOS and PFCAs in this food web was shown to occur to a similar extent as in marine food webs. In caribou and moose, PFASs were the major POPs with concentrations in liver ranking ahead of PCBs and PBDEs (ΣPFCAs> PFOS> ΣPCBs> ΣPBDEs). However, concentrations of new POPs and CUPs in caribou, moose, and other terrestrial animal samples were much lower compared with marine mammals, as observed for PCBs and OC pesticides in previous assessments.
The potential for climate warming to influence levels and trends of POPs in the arctic has emerged as a major line of investigation in the past 5 years. The relatively long time series for POPs now available e.g. ~18 years continuous measurement for air, 15 to 18 years of sampling over the past 35-50 years for lake trout, burbot, arctic char, seabirds, seals, polar bears, and beluga are beginning to be examined for possible linkages to climate variables (temperature, ice free times), as well as to parameters associated with dietary and species shifts (carbon and nitrogen stable isotope ratios, fatty acid signatures). For example, dietary tracers (carbon stable isotope ratios, fatty acid patterns) were found to explain trends of ΣPCB and ΣCHL in WHB polar bears. This result suggested that a dietary shift of polar bears to harbor seals, harp and bearded seals might lead to higher actual contaminant concentrations. Adjusting concentrations of ΣPCB and ΣDDT in murre eggs for trophic position resulted in little change in the calculated rate of decline of these legacy POPs at Prince Leopold Island in Lancaster Sound but reduced the rates of decline at Coats Island, in Hudson Strait, suggesting that the shift in diet which occurred in the murres at Coats Island has affected the contaminant temporal trends for that colony.
POPs monitoring programs, both abiotic and biotic, in the Arctic can provide valuable data to fingerprint the impact of arctic warming (Arctic amplification) on the environmental fate of POPs. However, there are still large uncertainties in understanding the influence of rapid climate change on the fate and mobilization of both legacy and new POPs in the Arctic. Although recent studies have revealed re-volatilization of POPs from arctic repositories, such as arctic waters, soils, snow/ice and permafrost, the actual net amounts released to atmosphere are not known, and whether a sink to source reversal in the Arctic is taking place also still remain unknown.
- Better data is required on key modeling parameters in food webs including efficiencies of uptake from water, air and food, and especially on the biotransformation rates that play a key role in biomagnification.
- The measurements in biological samples could be better synchronized with atmospheric measurements, where a greater number of chemicals are being analyzed in air e.g., novel BFRs and organophosphate flame retardants, siloxanes, and CUPs, both in the Canadian Arctic and in other air measurement programs.
7. Assessment of Biological effects remains a challenge
Assessing the effects of POPs on the health of Canadian arctic biota is very challenging due to factors such as low contaminant exposures, limited access to fresh samples, difficulties in processing samples in a way that suits the needs of health endpoints in the field, and a limited knowledge of life history and feeding ecology of many species. While toxicological studies of arctic wildlife remain challenging, recent investment in research under the NCP has increased the understanding of the effects of persistent contaminants on high trophic level biota and helped to develop new biochemical tools to assess effects.
There remains minimal evidence that POPs have widespread effects on the health of Canadian arctic animals. The best evidence for effects in top predators are from studies of East Greenland and Svalbard polar bears, as well as Svalbard glaucous gulls, which have much higher exposures to most POPs than in the Canadian Arctic. However, studies at the PCB contaminated site at Saglek Bay have demonstrated declines in the concentrations of PCBs in sediment, in biota, and in biological effects in the marine environment over time, illustrating that the tools and knowledge are available to assess effects where relatively high exposures are documented. PCB concentrations in shorthorn sculpin and black guillemot nestlings at Saglek Bay are below concentrations (1,000 ng g-1 ww) previously associated with risks of impaired reproduction and survival.
ΣPCB concentrations in beluga and polar bears exceed the toxicity reference value for immunotoxicity and endocrine disruption of 1.3 µg g−1 lw in harbor seals. Mean ΣPCB concentrations in Canadian arctic seabird eggs are well below reported thresholds for egg mortality and hatching success in fish-eating birds (except for glaucous gulls). Concentrations of PFOS in polar bear livers exceed the estimated no-effects values but PFOS levels in liver of birds and seals were an order of magnitude below no effects values.
- The development, validation and application of new genomics methods provides a powerful means of examining the relationship between physiological endpoints and persistent contaminants and should be applied to examine subtle effects on higher trophic level arctic animals.
- For studies of biological effects as well as effects of climate change on exposure to POPs, emphasis should be placed on the multiple ecological, biological, and physical (natural and anthropogenic) variables that need to be considered when analyzing contamination in species and when comparing data between studies.
- Date modified: