The Arctic at Risk:
A Circumpolar Atlas of Environmental Concerns
The Arctic at Risk:
Polychlorinated biphenyls (PCBs) are chlorinated organic compounds once manufactured in industrialized nations largely for industrial use. There are 209 possible different PCBs, known as congeners. Individual PCB congeners are seldom the focus of interest beyond the laboratory, principally because commercial PCBs contain a mixture of several congeners. In the US, PCB products manufactured by the Monsanto Company are called Aroclor.
PCBs have the ability to dissolve in fats or oils, they have remarkable chemical stability, and they are resistant to many biological, chemical, and physical processes, including high temperatures. PCBs do not easily dissolve in water, but adsorb to soil, underwater sediments, and animal membranes. Once in an animal's body, PCBs tend to remain stored in fat, often for long periods.
The fate of PCBs within an animal depends on the species, as well as the health, age, sex, activity level, etc., of the individual. Specifically, large, long-lived animals tend to bioaccumulate more of these (and similar) chemicals during their lifetime. However, these tendencies are not absolute, for example, the concentration of PCBs in ringed seal blubber increases with age in males, but not in females. Marine mammals are particularly at risk because their bodies also have high fat content.
PCBs are chemically similar to compounds known as dioxins and furans. Dioxins contain two oxygen atoms; furans contain one within the structure. Together the dioxins, furans, and PCBs, which are similar in function (notably at the molecular level), are referred to as the dioxin-like compounds.
Production and Use
PCBs do not occur naturally. They have been used since the early 1930's for a variety of purposes due to their resistance to chemical attack and their ability as flame retardants. PCBs were once commonly used in electrical equipment (transformers, circuit breakers, capacitors), heat transfer systems, manufacture of paints, plastics, adhesives, coating compounds, hydraulic systems, and pressure-sensitive copying paper (Meyer, 1989; Clark, 1992). These chemicals are either oily liquids or solids, and are odorless and colorless, or perhaps light yellow in color.
Worldwide production is estimated at 1.2 million tons (Chambers, 1994). By 1969 about one- third of the total production had been discharged into the environment (Chambers, 1994). The manufacture and use of PCBs declined once evidence indicated that they cause a range of harmful effects and build up in the environment and living systems. Although production of PCBs was banned in the United States in 1977, some systems using PCBs continue to operate, generally under enclosed conditions (Meyer, 1989).
Manufacturing facilities, electrical generating and transformer stations, and disposal sites are among the most common original sources. Today most of the PCBs in the United States and western Europe originate from sediment contaminated years ago, as well as accidentally leaking storage sites, including landfills. Military wastes at Distant Early Warning (DEW) sites in the North American Arctic contribute some local PCB contamination (Thomas et al., 1992). In addition, manufacturing and disposal practices continue the incidental release of PCBs into the environment. In the United States, release of PCBs may still occur in discharge from paint and ink formulating, metal finishing, and wood chemicals production (EPA, 1988).
Transport Pathways
While in use, PCBs were released into the air and water during their manufacture, and in leaks or spills during use, disposal, and transfer or transport. The atmospheric residence time for PCBs may be more than 45 days (Bidleman et al., 1981; Manchester-Neesvig and Andren, 1989). Terrestrial animals in the Arctic appear to be ingesting PCBs on plant surfaces that have deposited from the atmosphere attached to particles (Thomas et al., 1992).
PCBs enter river estuaries through runoff from industrialized watersheds and deposition from the atmosphere. Because of their particle affinity, in seawater PCBs tend to deposit with sediment on the seabed (Muir and Norstrom, 1994). Here they may be ingested by filter-feeding organisms.
PCBs also accumulate at the air/sea interface, which encompasses the upper few um to 1 mm of the sea. Here concentrations of PCBs may be 100 to 10,000 times greater than those in the water column (Hardy, 1982), and can affect plankton and birds.
According to Dewailly et al. (1993), the inhalation of PCBs from ambient air and the consumption of drinking water are probably negligible contributors to human exposure in the Arctic. Surveys of indigenous populations on Broughton Island found that ingestion of narwhals and seals, as well as walrus and caribou, was the main source of PCB contamination (Kinloch et al., 1992).
Environmental Distribution
The presence of PCBs in air emissions, water discharges, and solid waste, as well as some products, has distributed these chemicals broadly throughout the globe. Clearly the highest concentrations are in industrialized nations, and these same nations contain disposal sites with large amounts of PCBs. For example, PCBs are found in air samples, soils, and water from many areas throughout the United States (ATSDR, 1990). The National Ocean Survey of the National Oceanic and Atmospheric Administration (NOAA) found PCBs in the sediments of every major coastal harbor and river in the United States, with concentrations directly related to port and population size of the surrounding area (NOS, 1990).
Although present in air and water, the concentrations are usually quite low, because PCBs have a greater tendency to attach to particles. Once in soils and sediments, PCBs are broken down slowly, and tend to remain attached to the sediment unless taken up by animals. Animals such as fish, worms, crabs, and cattle may accidentally consume contaminated sediments or soil during feeding. Some invertebrates, such as earthworms, feed by ingesting soil or sediment. Once taken up, PCBs accumulate in animals' fat deposits.
This uptake and accumulation in animals, and the low levels in air and dissolved in water, means that the primary route of exposure for animals, including people, is through food.
Freshwaters in major drainage basins of the United States have concentrations of PCBs ranging from 10 to 50 ng/l (Cordle et al., 1982). Worldwide, levels of PCBs may exceed 100 ng/l in polluted estuaries, while they generally are around 1 ng/l in coastal areas and 0.1 ng/l in the open sea (Kennish, 1994). Typical North Atlantic levels of PCBs in seawater are 0.026 ng/l (Iwata et al., 1993). Contamination of the ocean by PCBs is more evenly distributed between the Northern and Southern hemispheres than for DDTs or HCHs. In the past decade, oceanic PCB levels have become uniform in response to decreased use by developed countries in mid-latitudes, while input from developing nations continues at low latitudes (Iwata et al., 1993). Iwata et al. (1993) propose that PCBs may be volatilized from surface waters in the tropics, while the cold Arctic waters serve as a significant sink for less-chlorinated PCB congeners.
In the Arctic, recent studies of the Chukchi and Bering seas and the Gulf of Alaska indicate PCB concentrations of .008 to .012 ng/l (Iwata et al., 1993). While elevated concentrations have been reported for some of the coastal regions of the Kara and Laptev seas (greater than 10 ng/l; Melnikov and Vlasov 1992), interlaboratory comparisons indicate that there may be problems with the quality of these PCB analyses. Note, however, that recent measurements in the Laptev Sea also indicate elevated levels in this nearby region (Kassens, pers. comm.). There are virtually no PCB data from the central Arctic Ocean that could indicate if contaminated coastal waters might be making their way offshore.
McCrea and Fischer (1986) also observed high levels of PCBs in Ontario rivers that drain into Hudson Bay (5 ng/l). According to Kinloch et al. (1992), the DEW sites do not appear to contribute to the regional PCB pollution in this area.
Much lower PCB values are observed near the Canadian Arctic Islands (Hargrave et al., 1988) and eastern Greenland (Gaul in press).
Interestingly, the sea ice in this region has higher levels than the seawater. Sea ice north of Svalbard exceeds 15 ng/l, while ice between Greenland and Svalbard is 2.5 ng/l (Gaul, in press).
Polar bears at the top of the food chain (fifth trophic level; Welch et al., 1992) have higher levels of PCBs than do other Arctic biota (Muir and Norstrom, 1994). PCBs in the fat of polar bears have been studied relatively thoroughly in the Canadian Arctic (Norstrom et al., 1988). Their geographic distribution indicates a relatively uniform distribution of PCB contamination in North America. However, on Svalbard, the levels are higher, ranging from 2.9 to 90 ug/g (Norheim et al., 1992). This spatial trend, also observed in their main prey, ringed seals, suggests that sources of PCBs in northern Europe and eastern Asia are contaminating the marine food chain (Muir and Norstrom, 1994).
According to Dewailly et al. (1993), concentrations of PCBs in the milk fat of Inuit women in Arctic Quebec was similar to that found in beluga blubber. This level is seven times greater than that found in Arctic char, and seven times greater than that measured in the milk fat of southern Quebec women. Consumption of PCB-contaminated ringed seal and beluga blubber and of beluga skin (muktuk) appears to be the source of the PCBs in the Arctic Quebec Inuit population. For reference, note that the levels of PCBs in polar bear fat were seven times greater than in that of Inuit milk fat.
Studies of temporal trends in PCBs indicate that, as expected, levels in ringed seals and seabirds have declined significantly since the early 1970's to 1980's (Muir et al., 1992), due to decreases in the use of PCBs. Deposition of PCBs from the atmosphere appears to have decreased by about a factor of two since 1970, based on studies of annual snow layers in the Agassiz Ice Cap on Ellesmere Island, Canada (Gregor, 1991).
Potential Health Effects
Health hazards from environmental, food chain, and occupational exposure to PCBs is difficult to evaluate, in part because exposure is often concomitant with other toxicants. Also, the important effects on human health are typically 1) those associated with chronic exposure, which develop slowly after a pulse of exposure or long-term exposure to low doses, and 2) subtle effects on development that may occur following prenatal exposure (Chambers, 1994).
Once ingested, PCBs are distributed into tissues in the thymus, lungs, spleen, kidneys, liver, brain, muscle, and testes, and cause pathological changes in the immune and reproductive systems. PCBs cause neurobehavioral disorders, birth anomalies, are animal carcinogens, and enhance the cancer-causing capability of other carcinogens (Meyer, 1989). Because PCBs cross the placental barrier and bioconcentrate in milk fat, fetuses and breast-fed babies are the most heavily exposed population, as well as being the most vulnerable to health consequences (Dewailly et al., 1993). Immunotoxic effects of PCBs may be relevant in understanding the high incidence of infectious diseases noted in Inuit infants from Arctic Quebec (Dewailly et al., 1993).
PCBs appear to mimic estrogen and result in abnormal sexual development and impaired reproduction. The presence of PCBs and other contaminants in belugas in the St. Lawrence estuary has been implicated in lower reproductive rates in comparison to Arctic animals (Sergeant and Hoek, 1988; Martineau et al., 1987). Eggs of birds contaminated with PCBs show reduced hatchability (Clark, 1992).
The US Food and Drug Administration (FDA) recommends values of 0.2 - 2.0 ug/g (ppm) to protect humans from consumption of contaminated food (ATSDR, 1993). The US EPA standard for fresh water is 1 ng/l, the same as the Canadian Council of Resource and Environment Ministers (CCREM) water-quality criteria for the protection of freshwater life (Lockhart et al., 1992). The Canadian tolerable level of PCB contamination of fish is 2 ug/g (ppm), based on a weekly consumption of a quarter pound (100 g) of the edible portion of the fish (Kinloch et al., 1992). The atmospheric maximum permissible concentration recommended by US National Institute of Occupational Safety and Health is 1 ug/m3.
The maps show that some rivers and sea ice have PCB levels in excess of 1 ng/l, which exceeds the standards for protection of freshwater life.
In addition, the livers of thick-billed murres, northern fulmars, walrus, ringed seals, and polar bears often exceed the 0.2 - 2.0 ug/g
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| Arctic Cod | Northern Fulmar | Thick-Billed Murre | |
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| Walrus | Beluga | ||
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| Ringed Seals | Polar Bears | Arctic Char | |
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| Caribou-Reindeer | Water | Ice |
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