Sean Backus

Contaminants in the Canadian Arctic: 5 years of progress in understanding sources, occurrence and pathways

Recent studies of contaminants under the Canadian Northern Contaminants Program (NCP) have substantially enhanced our understanding of the pathways by which contaminants enter Canadas Arctic and move through terrestrial and marine ecosystems there. Building on a previous review (Barrie et al., Arctic contaminants: sources, occurrence and pathways. Sci Total Environ 1992:1-74), we highlight new knowledge developed under the NCP on the sources, occurrence and pathways of contaminants (organochlorines, Hg, Pb and Cd, PAHs, artificial radionuclides). Starting from the global scale, we examine emission histories and sources for selected contaminants focussing especially on the organochlorines. Physical and chemical properties, transport processes in the environment (e.g. winds, currents, partitioning), and models are then used to identify, understand and illustrate the connection between the contaminant sources in industrial and agricultural regions to the south and the eventual arrival of contaminants in remote regions of the Arctic. Within the Arctic, we examine how contaminants impinge on marine and terrestrial pathways and how they are subsequently either removed to sinks or remain where they can enter the biosphere. As a way to focus this synthesis on key concerns of northern residents, a number of special topics are examined including: a mass balance for HCH and toxaphene (CHBs) in the Arctic Ocean; a comparison of PCB sources within Canadas Arctic (Dew Line Sites) with PCBs imported through long-range transport; an evaluation of concerns posed by three priority metals--Hg, Pb and Cd; an evaluation of the risks from artificial radionuclides in the ocean; a review of what is known about new-generation pesticides that are replacing the organochlorines; and a comparison of natural vs. anthropogenic sources of PAH in the Arctic. The research and syntheses provide compelling evidence for close connectivity between the global emission of contaminants from industrial and agricultural activities and the Arctic. For semi-volatile compounds that partition strongly into cold water (e.g. HCH) we have seen an inevitable loading of Arctic aquatic reservoirs. Drastic HCH emission reductions have been rapidly followed by reduced atmospheric burdens with the result that the major reservoir and transport agent has become the ocean. In the Arctic, it will take decades for the upper ocean to clear itself of HCH. For compounds that partition strongly onto particles, and for which the soil reservoir is most important (e.g. PCBs), we have seen a delay in their arrival in the Arctic and some fractionation toward more volatile compounds (e.g. lower-chlorinated PCBs). Despite banning the production of PCB in the 1970s, and despite decreases of PCBs in environmental compartments in temperate regions, the Arctic presently shows little evidence of reduced PCB loadings. We anticipate a delay in PCB reductions in the Arctic and environmental lifetimes measured in decades. Although artificial radionuclides have caused great concern due to their direct disposal on Russian Shelves, they are found to pose little threat to Canadian waters and, indeed, much of the radionuclide inventory can be explained as remnant global fallout, which was sharply curtailed in the 1960s, and waste emissions released under license by the European reprocessing plants. Although Cd poses a human dietary concern both for terrestrial and marine mammals, we find little evidence that Cd in marine systems has been impacted by human activities. There is evidence of contaminant Pb in the Arctic, but loadings appear presently to be decreasing due to source controls (e.g. removal of Pb from gasoline) in Europe and North America. Of the metals, Hg provokes the greatest concern; loadings appear to be increasing in the Arctic due to global human activities, but such loadings are not evenly distributed nor are the pathways by which they enter and move within the Arctic well understood.

Toxicity of oil sands to early life stages of fathead minnows (Pimephales promelas)

The present study examines the effects of exposure to oil sands on the early life stages (ELS) of fathead minnows (Pimephales promelas). Sediments within and outside natural oil sand deposits were collected from sites along the Athabasca River (AB, Canada). The ELS toxicity tests were conducted with control water, natural oil sands, reference sediments, and oil-refining wastewater pond sediments. Eggs and larvae were exposed to 0.05 to 25.0 g sediment/L and observed for mortality, hatching, malformations, growth, and cytochrome P4501A induction as measured by immunohistochemistry. Natural bitumen and wastewater pond sediments caused significant hatching alterations and exposure-related increases in ELS mortality, malformations, and reduced size. Larval deformities included edemas, hemorrhages, and spinal malformations. Exposure to reference sediments and controls showed negligible embryo mortality and malformations and excellent larval survival. Sediment analyses using gas chromatography-mass spectrometry revealed high concentrations of alkyl-substituted polyaromatic hydrocarbons (PAHs) compared to unsubstituted PAHs in natural oil sands (220-360 microg/g) and oil-mining wastewater pond sediments (1,300 microg/g). The ELS sediment toxicity tests are rapid and sensitive bioassays that are useful in the assessment of petroleum toxicity to aquatic organisms.

Changes in mercury levels in great lakes fish between 1970s and 2007.

A number of initiatives have curtailed anthropogenic mercury emissions in North America over the last two decades; however, various factors, including long-range transport of global emissions, may complicate the response of fish mercury levels to remedial actions. Since the Great Lakes of North America are together the largest surface freshwater body in the world and are under the influence of many complicating factors, trends of mercury in fish from the Great Lakes can reflect the overall impact of mercury management actions at local, regional, and perhaps global scales. Here we present a comprehensive view of mercury trends in Canadian Great Lakes fish using two large (total 5807 samples), different (fillet and whole fish), and long-term (1970s-2007) monitoring data sets. The spatial differences in lake trout and walleye mercury levels during this period have generally been within a factor of 2-3 with Lakes Erie and Superior having the lowest and highest concentrations, respectively. These spatial differences have diminished in the recent years (2000-2007). The concentrations have generally declined over the three decades (mid-1970s to 2007); however, in recent years, the concentration trends are flat in Lake Ontario walleye and appear to be increasing in Lake Erie walleye. There was a mismatch in the Lake Ontario lake trout and walleye temporal trends, which shows the importance of considering more than one fish species for proper spatial/temporal trend assessments.

Spatial patterns and temporal trends in mercury concentrations, precipitation depths, and mercury wet deposition in the North American Great Lakes region, 2002-2008

Annual and weekly mercury (Hg) concentrations, precipitation depths, and Hg wet deposition in the Great Lakes region were analyzed by using data from 5 monitoring networks in the USA and Canada for a 2002-2008 study period. High-resolution maps of calculated annual data, 7-year mean data, and net interannual change for the study period were prepared to assess spatial patterns. Areas with 7-year mean annual Hg concentrations higher than the 12 ng per liter water-quality criterion were mapped in 4 states. Temporal trends in measured weekly data were determined statistically. Monitoring sites with significant 7-year trends in weekly Hg wet deposition were spatially separated and were not sites with trends in weekly Hg concentration. During 2002-2008, Hg wet deposition was found to be unchanged in the Great Lakes region and its subregions. Any small decreases in Hg concentration apparently were offset by increases in precipitation.

Detection of a Cyclic Perfluorinated Acid, Perfluoroethylcyclohexane Sulfonate, in the Great Lakes of North America

Perfluoroethylcyclohexanesulfonate (PFECHS) is a cyclic perfluorinated acid (PFA) mainly used as an erosion inhibitor in aircraft hydraulic fluids. It is expected to be as recalcitrant to environmental degradation as aliphatic PFAs including perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS). For the first time, PFECHS is reported in top predator fish (<MDL to 3.7 ng g(-1) wet weight in whole body homogenate) from the Great Lakes and in surface waters (0.16-5.7 ng L(-1)). PFOS was the major aliphatic PFA in fish from the Great Lakes. Concentrations of most of the PFAs were not statistically different from previously reported 2004 trout data in Lake Ontario. Shorter chain perfluorocarboxylates were prevalent in surface waters of the Great Lakes, dominated by PFOA (0.65-5.5 ng/L). An impurity in the commercial PFECHS formulation, perfluoromethylcyclohexane sulfonate (PFMeCHS), was also detected in the dissolved phase but not above detection limits in fish tissue. Bioaccumulation factors (BAFs) were estimated by taking the ratio of fish to water concentrations. The mean log BAF values corresponded to 2.8 for PFECHS, 2.1 for PFOA, and 4.5 for PFOS. It is not certain whether the fish-water BAF for PFECHS is an overestimate due to the influence of precursor biotransformation. Further studies are recommended to understand the extent of PFECHS contamination.

Spatiotemporal trends of mercury in walleye and largemouth bass from the Laurentian Great Lakes Region

The risk of mercury (Hg) exposure to humans and wildlife from fish consumption has driven extensive mercury analysis throughout the Great Lakes Region since the 1970s. This study compiled fish-Hg data from multiple sources in the region and assessed spatiotemporal trends of Hg concentrations in two representative top predator fish species. Walleye (Sander vitreus) and largemouth bass (Micropterus salmoides) were chosen for the trend analysis because they had more Hg records (63,872) than other fish species that had been sampled from waters throughout the region. Waterbody types were inland lakes (70%), the Great Lakes, impoundments, and rivers. The compiled datasets were analyzed with a mixed effects statistical model having random effects of station, year, and fish length; and fixed effects of year, tissue type, fish length, habitat, and season. The results showed a generally declining temporal trend in fish-Hg for the region (1970–2009), with spatial trends of increasing Hg concentration from south to north and from west to east across the region. Nonlinearity was evident in the general downward trends of Ontario walleye, with a shift to an upward trend beginning in the 1990s. Only ongoing monitoring can reveal if this upward shift is an oscillation in a long-term decline, a statistical anomaly, or a sustained declining temporal trend in regional fish-Hg concentrations.

From the city to the Lake: loadings of PCBs, PBDEs, PAHs and PCMs from Toronto to Lake Ontario.

Loadings from Toronto, Canada to Lake Ontario were quantified and major sources and pathways were identified, with the goal of informing opportunities for loading reductions. The contaminants were polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs) and polycyclic musks (PCMs). Loadings were calculated from measured concentrations for three major pathways: atmospheric processes, tributary runoff, and wastewater treatment plant (WWTP) effluents. Although atmospheric deposition to the Great Lakes has received the greatest attention, this was the dominant loading pathway for PCBs only (17 ± 5.3 kg/y or 66% of total loadings). PCB loadings reflected elevated urban PCB air concentrations due to, predominantly, primary emissions. These loadings contribute to consumption advisories for nearshore fish. PBDE loadings to the lake, again from mainly primary emissions, were 48% (9.1 ± 1.3 kg/y) and 42% (8.0 ± 5.7 kg/y) via tributaries and WWTPs, respectively, consistent with emissions deposited and subsequently washed-off of urban surfaces and emissions to the sewage system. PAHs loadings of 1600 ± 280 kg/y (71%) from tributaries were strongly associated with vehicle transportation and impervious surfaces. PCM loadings were 83% (±140 kg/y) from WWTP final effluent, reflecting their use in personal care products. Opportunities for source reduction lie in reducing the current inventories of in-use PCBs and PBDE-containing products, reducing vehicle emissions of PAHs and use of PAHs in the transportation network (e.g., pavement sealants), and improving wastewater treatment technology.

Enantiospecific Perfluorooctane Sulfonate (PFOS) Analysis Reveals Evidence for the Source Contribution of PFOS-Precursors to the Lake Ontario Foodweb

Exposure to perfluorooctane sulfonate (PFOS) may arise directly, from emission and exposure to PFOS itself, or indirectly via the environmental release and degradation of PFOS-precursors. Human serum enantiomer fractions (EFs) of 1m-PFOS have been shown to be nonracemic, suggesting that PFOS-precursors are a significant source of PFOS in humans, but little is known about the importance of PFOS-precursors in ecosystems. In the current work, concentrations of PFOS, perfluorooctane sulfonamide (PFOSA), PFOS isomer profiles, and EFs of 1m-PFOS were determined in Lake Ontario water, sediment, fishes and invertebrates. Concentrations of PFOS and PFOSA were highest in slimy sculpin and Diporeia, and concentrations of the two compounds were often correlated. 1m-PFOS was racemic in sediment, water, sculpin and rainbow smelt, but nonracemic in the top predator, lake trout, and all invertebrate species. Furthermore, EFs were correlated with the relative concentrations of PFOS and PFOSA in invertebrates. Overall, these empirical observations with a new analytical tool confirm previous suggestions that PFOS-precursors contribute to PFOS in the food web, likely via sediment. Implications are that future PFOS exposures in this ecosystem will be influenced by an in situ source, and that the apparent environmental behavior of PFOS (e.g., bioaccumulation potential) can be confounded by precursors.

Temporal PCB and mercury trends in Lake Erie fish communities: A dynamic linear modeling analysis

We performed dynamic linear modeling analysis on fish contaminant data collected from the Ontario Ministry of the Environment and Environment Canada to examine long-term trends of total mercury (THg) and polychlorinated biphenyls (PCBs) in Lake Erie. Several sport fish species (walleye, smallmouth bass, rainbow trout) with differences in their diet habits, food competition strategies and foraging patterns are characterized by weakly increasing trends of their THg levels in Lake Erie after the mid- or late 1990s. Similarly, our analysis shows that the decline rates of the PCB body burdens in white bass, smallmouth bass, freshwater drum and whitefish have slowed down or have switched to weakly increasing rates over the last decade. Our analysis also provides evidence that the rainbow trout and coho salmon PCB concentrations have been decreasing steadily but the associated rates were fairly weak. The systematic shifts in energy trophodynamics along with the food web alterations induced from the introduction of non-native species, the new role of the sediments as a net contaminant source, and the potentially significant fluxes from the atmosphere stand out as some of the hypotheses proposed to explain the limited Lake Erie response in recent years to the various contamination mitigation strategies.

Concentrations and trophic magnification of cyclic siloxanes in aquatic biota from the Western Basin of Lake Erie, Canada

We examine the concentrations and food web biomagnification of three cyclic volatile methylsiloxanes (cVMS) octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) using aquatic biota collected from Lake Erie. Concentrations of cVMS in biota were within the range reported for other studies of cVMS in aquatic biota. Trophic magnification factors (TMF) were assessed in various food web configurations to investigate the effects of food web structure. TMF estimates were highly dependent on the inclusion/exclusion of the organisms occupying the highest and lowest trophic levels and were >1 for D4 and D5, indicating biomagnification, in only 1 of the 5 food web configurations investigated and were <1 in the remaining 4 food web configurations. TMF estimates for PCB180 were also dependant on food web configuration, but did not correspond with those obtained for cVMS materials. These differences may be attributed to environmental exposure and/or lipid partitioning differences between PCB180 and cVMS.