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Recovery of peregrine falcons in Canada

Photo: peregrine falcon © Gordon Court

The story of the peregrine falcon shows that contaminants can have major effects on biodiversity and that banning and restricting contaminants works. Peregrines in Canada declined dramatically from the 1950s to 1970s, mainly from egg-shell thinning caused by DDT and its breakdown products.6 With the banning of DDT in Canada in 1970, 1972 in the U.S., and 2000 in Mexico, DDT slowly declined in the environment. Conservation actions and reintroductions helped populations to increase once DDT levels were low enough for eggs to hatch successfully. Some parts of Canada such as the Okanagan Valley of British Columbia may still have too much legacy DDT for peregrine falcons to nest successfully.7

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Number of sites occupied by peregrines, 1970 to 2005
Graph: number of sites occupied by peregrines. Click for graphic description (new window).
Long description for Recovery of peregrine falcons in Canada

This bar graph shows the increase in the number of sites occupied by peregrine falcons in Canada from 1970 to 2005. The number of sites occupied was as follows: 94 in 1970; 123 in 1975; 180 in 1980; 224 in 1985; 400 in 1990; 443 in 1995; 523 in 2000; and 662 in 2005.

Source: data from COSEWIC, 20076

Contaminant trends

Parts per million, logarithmic scale
Map and graphs: contaminant trends in various species across Canada. Click for graphic description (new window.)
Long description for Contaminant trends

This graphic shows contaminant levels in several wild species at locations throughout Canada, over a range of time periods. The locations of the eight charts included in this graphic are shown on a map of Canada. Each chart consists of a set of line graphs of contaminants levels for individual species at one location, with the contaminant types and the years plotted depending upon what data were available. The units for all the contaminants in all charts are parts per million, abbreviated as ppm. The data points are plotted and joined with lines – there are no statistical trend lines included. Overall, the charts show mainly decreasing trends of PCBs and DDE or DDTs, varying trends in mercury levels, and overall increases in PBDEs. The increasing trends of PBDEs generally stopped or were reversed in recent years. Unless otherwise indicated in the descriptions below, the two years for which values are presented are the first and the most recent years of sampling.

Each graph is described in the following set of points, by location:

  1. This chart shows contaminants in eggs of thick-billed murres from Prince Leopold Island in the Arctic. PCBs decreased (with values of 2.4 ppm in 1975 and 0.97 ppm in 2008). Total DDTs decreased (2.0 ppm in 1975 and 1.2 ppm in 2008). Mercury levels increased (0.6 ppm in 1975 and 1.5 ppm in 2009). PBDEs showed an overall increase followed by a recent decline, rising from very low levels of 0.0044 ppm in 1975 and peaking at 0.046 ppm in 2006, then decreasing to 0.015 ppm in 2008.
  2. This chart shows contaminants in beluga blubber from the vicinity of Pangnirtung in the Arctic Archipelago. PCBs decreased (4.1 ppm in 1982 and 2.7 ppm in 2008). Total DDTs in decreased (5.1 ppm in 1982 and 1.3 ppm in 2008). PBDEs increased (0.004 ppm in 1982 and 0.021 in 2008, with levels fluctuating but not increasing since about 2000). Mercury data were not available.
  3. This chart shows contaminants in eggs of double-crested cormorants from the St. Lawrence Estuary. PCBs decreased (16 ppm in 1972 and 3.1 ppm in 2004). DDE levels decreased (5.6 ppm in 1972 and 0.55 ppm in 2004). Mercury and PBDE data were not available.
  4. This chart shows contaminants in eggs of double-crested cormorants from the Bay of Fundy. PCBs decreased (19 ppm in 1972 and 1.3 ppm in 2004). DDE levels decreased (6.6 ppm in 1972 and 0.31 ppm in 2004). Mercury and PBDE data were not available.
  5. This chart shows contaminants in lake trout from Lake Ontario. PCBs decreased (6.3 ppm in 1982 and 1.2 ppm in 2002). Total DDT levels also decreased over the same time period (1.9 ppm in 1982 and 0.63 ppm in 2002). The levels of PBDEs increased (0.27 ppm in 1979, rising to 3.3 ppm in 1993) and then began to decrease, with the most recent measurement being 1.7 ppm in 2004). Mercury data were not available.
  6. This chart shows contaminants in eggs of herring gulls from Lake Ontario. PCBs decreased more than an order of magnitude (9.5 ppm in 1981 and 0.41 ppm in 2005), as did DDE (23 ppm in 1974 and 1.6 ppm in 2007). Mercury levels decreased (0.46 ppm in 1974 and 0.30 ppm in 2007). PBDEs increased, with the trend leveling off in recent years (0.009 ppm in 1981 and 0.41 ppm in 2005).
  7. This chart shows contaminants in eggs of double-crested cormorants in the Strait of Georgia. PCBs decreased more than an order of magnitude (14 ppm in 1970 and 0.84 ppm in 2002). DDE decreased (4.07 ppm in 1970 and 1.38 ppm in 2002). PBDEs increased steeply until the mid 1990s (0.0002 ppm in 1979 and 0.39 ppm in 1994), followed by a slower decline (0.063 ppm in 2002). Mercury data were not available.
  8. This chart shows contaminants in Mackenzie River burbot. PCBs show little trend, fluctuating in the range of 0.11 to 0.28 ppm from 1988 to 2008. Total DDT also showed no trend from the mid 1980s to the early 2000s (fluctuating in the range of 0.05 to 0.06 ppm), then showed more variability and some higher peaks (fluctuating in the range of 0.06 to 0.17 ppm in annual measurements from 2002 to 2008). PBDEs increased sharply (0.0004 ppm in 1988 and 0.0052 ppm in 2006) and then declined steeply in the most recent two years of sampling (0.0020 in 2007 and 0.00094 in 2008). Mercury increased (0.22 ppm in 1985 and 0.41 in 2008).
Sources: burbot: Stern, 2009;8 murres: Braune, 20079 updated by author; beluga: Stern, 200910 and Tomy, 2009;11 cormorants and gulls: Environment Canada, 2009;12 lake trout: Carlson et al., 201013 and Ismail et al., 200914

The charts show a range of trends and levels of two legacy contaminants (PCBs and DDT), mercury, and an emerging contaminant (PBDEs) in wildlife. Amounts and trends are partly related to proximity to contaminant sources and partly to otherfactors that influence an animal's exposure to and uptake of contaminants, including position in the food web. Magnitudes ofcontaminant levels should be compared from chart to chart only in general terms - datasets are not all comparable in the types of tissues sampled and in analysis and data reporting methods.

Note: DDE is a breakdown product of DDT.

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Trends in contaminants in the Great Lakes

Trends in contaminants in the Great Lakes Legacy contaminants and mercury are generally decreasing in the Great Lakes in response to clean-up of contaminated sites and improved pollution control.4, 13 However, the large volumes of water and sediment in the system act as a storehouse – contaminants continue to be released from sediments and to recycle through the water, sediment, and food webs.19, 20 Contaminants also continue to be deposited into the lakes through long-range atmospheric transport21 and, in the case of mercury, from industrial emissions in the Great Lakes Basin.4 The net result is that rates of decline of some legacy contaminants and mercury have slowed in areas of the Great Lakes, leaving some contaminants at levels that are of concern and likely to remain so for some time to come.13, 20

Brominated flame retardants (PBDEs) increased rapidly in fish and birds starting in the early 1980s,22-24 but levels have now stabilized or are declining in response to action taken to curtail the use and release of these substances.24, 25 Many other emerging contaminants have been detected more recently in environmental samples, often in trace amounts, but little is known about the risk to ecosystems from most of them.26 Chemicals of concern include PFOS, originating in water-repellent coatings and fire-suppression foam, detected in fish samples throughout the Great Lakes, and known to build up in food webs.27 Emerging contaminants also include endocrine disrupting substances, which come from a range of sources, including pharmaceuticals. Potential effects include abnormal gonad development in fish.28 Many emerging contaminants do not originate in industrial emissions, but rather from use and disposal of health and personal-care products and consumer goods, leading to a need for new risk management approaches for contaminants in the Great Lakes.26

Interactions between contaminants and environmental change

Changes in environmental conditions caused by stressors, including climate change and invasive non-native species, may, in some cases, make wildlife more vulnerable to contaminants. Environmental change can increase the exposure of some aquatic species to contaminants through changes in water flow and chemistry and through changes in food webs.15, 16 Interactions may also make animals more vulnerable to the effects of contaminants. For example, salmonids in the Great Lakes have switched to a diet that includes alewife, an invasive non-native fish, leading to thiamine (vitamin B1) deficiencies that may interact with the effects of contaminants like PCBs to increase mortality rates in young fish.17

Impact of less sea ice on contaminants in seals and polar bears

Photo: bearded seal © changes in sea-ice conditions, western Hudson Bay polar bears are feeding less on
ice-associated bearded seals (which eat invertebrates) and more on open-water seals (which eat fish).18 Because fish-eating seals have higher levels of contaminants, some legacy contaminants in polar bears may not be declining as much as would be expected if their diet had not changed and levels of emerging contaminants may be increasing at a faster rate. Concentrations of brominated flame retardants (PBDEs) in western Hudson Bay polar bears are estimated to have increased 28% faster from 1991 to 2007 than would have occurred if the bears had not changed their diet.18

Impact of changes in fire regimes on mercury in fish

Photo: fireweed © in fire regimes can increase algae in lakes and contaminants in fish. A study in Jasper National Park16 found that fire in the catchment area of a lake in 2000 increased the input of nutrients to the lake over a period of several years. This led to an increase in production of algae, which led to an increase in the abundance of invertebrates, making the lake's food web more complex. The outcome was an increase in mercury accumulating in lake trout and rainbow trout.

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PCBs in Great Lakes fish

Total PCB concentrations in lake trout (walleye in Lake Erie) Parts per million (logarithmic scale), 1972 to 2002
Graph: PCBs in Great Lakes fish. Click for graphic description (new window).
Long description for PCBs in Great Lakes fish

This line graph shows the total PCB concentrations in lake trout (walleye in Lake Erie) in the Great Lakes, from 1972 to 2002. Data are shown for lakes Superior, Huron, Michigan, Erie and Ontario. PCB concentrations in fish declined in all the lakes from the early to mid 1970s to the mid 1980s. The highest PCB concentration was more than 10 parts per million in Lake Michigan lake trout in the early 1970s and the lowest was less than 0.5 parts per million in Lake Superior lake trout in the late 1980s. Since the mid 1980s, PCB levels in Great Lakes fish show slow declines or no trend.

Source: adapted from Carlson et al., 2010.13

PCBs in fish declined rapidly until the mid-1980s, halving in concentration every three to six years. Since then, PCBs in fish show either slow declines or no significant trend.13

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Effects of contaminants on wildlife

Persistent organic pollutants, as well as mercury, tend to accumulate in aquatic ecosystems more than in terrestrial ones. These levels are magnified as they move up the food web. This means that the highest levels of these contaminants are found in top predators – especially marine mammals and fish-eating birds.

There is no evidence of current widespread effects of contaminants on Canadian Arctic wildlife, though polar bears of southern and western Hudson Bay, as well as some high Arctic seabirds, have contaminant levels that may be placing them at risk.3 However, what is known is based only on studies of a few species and is usually based on the effects of a single contaminant. Little is known about impacts of the contaminant mixtures that wildlife are exposed to, or about interactions of contaminants with other changes in ecosystems.3

Contaminant levels are much higher in some areas of southern Canada than they are in the Arctic (see graphs of contaminant trends earlier in this section). Levels of contaminants measured in wildlife often exceed thresholds beyond which biological effects are known to occur from laboratory studies (usually based on species other than those of concern in the wild). While direct evidence of impacts on wildlife populations is difficult to obtain, associations between high contaminant levels and observations of effects – like tumours, abnormal gonads, or poor reproductive success17, 28 – underscore conservation-level concerns for some populations. The clearest example of known impacts is that of DDT-associated egg-shell thinning in birds29 – but high levels of contaminants are suspected to contribute to declines in several wildlife populations, for example, herring gulls in the Great Lakes30 and beluga whales in the St. Lawrence Estuary.31, 32

Contaminants in killer whales off the Pacific Coast

Average levels in killer whale biopsy samples, mid-1990s, parts per million
Map and graphs: concentration of contaminants in three killer whale populations off the Pacific coast. Click for graphic description (new window).
Long description for Contaminants in killer whales off the Pacific Coast

This graphic includes bar charts showing the average levels of PCBs and PBDEs in the three populations of killer whales along the B.C. coast from samples taken in the mid 1990s. The charts are accompanied by a map showing the distribution of the three populations. Northern resident whales reach from the coastal border with Alaska to approximately two thirds down the coast of Vancouver Island; the southern resident whales extend from below the northern resident territory through Puget Sound and off the northern Olympic Peninsula. The transient killer whale extends off the entire B.C. coast and through Puget Sound.

Average PCB levels were: transient whales, 250 parts per million; southern residents, 150 parts per million; and northern residents, 40 parts per million. These values are all well above the effects threshold for harbour seals, which is 10 parts per million. This effects threshold is the level at which toxic effects have been detected from PCBs in tests on harbour seals. Average PDBE levels were: transient whales, 1,000 parts per million; southern residents, 975 parts per million; and northern residents, 200 parts per million. Effects thresholds are not known for PBDEs in killer whales or related species.

Source: adapted from Ross, 200633

PCBs and PBDEs are known to adversely affect neurological development, reproductive development, and immune system function of marine mammals.33 Because they are long-lived top predators, killer whales accumulate high concentrations of persistent organic pollutants, including PCBs and PBDEs.29, 34, 35 The concentrations of PCBs in the three killer whale populations along the B.C. coast exceed levels known to affect the health of harbour seals,33 and the PCB levels of two populations are among the highest in marine mammals in the world.35

The large variation in contaminant concentrations among the populations is related to their feeding habits. Transient whales feed on marine mammals, placing them higher in the food web, while both resident populations feed largely on salmon that acquire contaminants from global sources in the North Pacific Ocean.29 Southern resident whales also feed on prey that pick up contaminants from the industrial coastal waters of southern B.C. and northwest Washington, leading to higher PCB and PBDE accumulation.29 These or other contaminants may be a factor in the decline of this endangered population of killer whales (see Marine Biome).36

Photo: killer whales ©
  Killer whales