PCB clean-up leads to quick recovery of Arctic wildlife.
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Brown, TM, TA Sheldon, NM Burgess and KJ Reimer. 2009. Reduction of PCB contamination in an Arctic coastal environment: A first step in assessing ecosystem recovery after the removal of a point source. Environmental Science and Technology doi:10.1021/es900941w. |
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| Quentin Goodman/Wikimedia Commons |
| PCB levels declined in black guillemots living in the Canadian Arctic after a nearby Superfund site was cleaned up. |
Context
PCBs were used extensively from the 1930s to the 1970s in electrical capacitors, transformers and a number of other applications. The chemicals have excellent insulating properties and do not break down when exposed to high temperatures or pressures. Their production and use in North America was stopped three decades ago because of their persistence in the environment and mounting health concerns.
Heavy use, improper disposal, resistance to breakdown and ability to travel long distances in air and water have led to widespread environmental contamination. Once in soil and water, the chemicals concentrate as they move through food chains from invertebrates to top predators. Eventually, the chemicals accumulate at levels high enough to affect the health of wildife – including fish, fish-eating birds and mammals – and people.
Arctic wildlife are some of the most contaminated animals in the world. Polar bears, seals and other Arctic creatures live long lives. They can store PCBs in their fat. As a result, aboriginal peoples eating fish, polar bears and seals also have high PCB levels in their bodies.
PCBs have been linked to cancers in animals and to effects on the immune, nervous and reproductive systems in wildlife and people. They are considered to be probable carcinogens in humans. Human exposure occurs mainly through food and most North Americans have measurable levels of PCBs in their blood.
Remote locations in the Arctic are contaminated with PCBs and other persistent pollutants that are either carried there by wind and water or released from local sources. For instance, the high use and improper disposal of transformers at military radar sites in the Arctic regions have created PCB-contaminated hotspots. Saglek Bay along the eastern shore of Labrador, Canada, is one military site that operated there from the 1950s to the 1970s. PCBs contaminated the military base and a nearby marine ecosystem after PCB-laden soils washed into the ocean.
At Saglek Bay, the PCB-contaminated soil (about 20,000 cubic meters) was excavated, removed and incinerated between 1997 and 2004 to remediate the site and reduce the input of PCBs into the local marine ecosystem.
What did they do?
Researchers collected sediments, fish and birds from a coastal beach area near the Saglek Bay Superfund site in the Canadian Arctic. The site had been remediated in 1998, and the contaminated soils cleaned up. It was not known if or how quickly the PCB levels in the nearby contaminated marine waters and sediments would decrease once the PCBs were removed.
Sediment samples and shorthorn sculpin were taken in 2006, while the black guillemot birds and eggs were collected in 2007. The samples were gathered during July and August.
Sculpin are small fish that live on the ocean bottom and feed mainly on insects. Black guillemots eat fish and are common to this part of the Arctic.
PCB levels were measured in the soil samples, fish livers, and bird livers and eggs. The levels were compared to the levels in these same species of fish and birds that were collected at the same time of the year in 1998 – when the area was cleaned of PCBs. Then, PCB levels exceeded the Canadian Environmental Quality Guidelines and threatened the survival and reproduction of the fish and birds.
What did they find?
PCB levels in the sediments, the sculpin and the guillemots at the sites closest to the historic contamination in Saglek Bay decreased by 10, 19 and 6 times, respectively. The declines of PCB levels in the fish and birds are directly related to the rapid declines in sediment PCB levels.
PCB levels in the guillemot nestlings are now below levels associated with decreased survival and effects on reproduction.
However, PCB levels measured in the sculpin still pose a risk to this species’ reproduction. In addition, sediment levels of PCBs still remain above those believed to cause ecological effects. Given time, both the fish and sediment levels are expected to eventually decline to levels that no longer pose health or ecological risks.
The decreases occurred much faster than expected, which is good news.
What does it mean?
Only eight years after PCB-laden soil was removed from a military radar station in the Canadian Arctic, PCB levels in the soil and marine fish and birds living nearby have decreased rapidly. Levels are either approaching or are below levels that will no longer pose a threat to their health.
The study's findings are good news and show that polluted areas can recover if the source of the pollutants is removed. This is the first study to show that Arctic sites contaminated with high levels of persistent pollutants can be remediated to a point where wildlife in the area can recover from the health and reproductive threats posed by the chemicals.
Surprisingly, this cold-weather site is recovering faster than some PCB-contaminated sites that have been cleaned up in the continental U.S. For example, a PCB-contaminated industrial site in South Carolina was designated a Superfund site. The site was remediated in the 1990s. PCB levels decreased by 10 to 50 percent in the sediment of a downstream lake. Yet, the contamination in the fish has not shown similar downward trends (Brenner et al. 2004).
In the Canadian Arctic, the birds living near the coastal area where this study was done now have PCB levels that are believed to not pose a health risk. Levels in the fish are dropping closer to levels that no longer pose a threat to their health. In addition, lower PCB levels in the animals also means lower risks for people – like the Innu and Inuit living near Saglek Bay – who rely on the area's fish and wildlife as a food source.
ResourcesBrenner, RC, VS Magar, JA Ickes, EA Foote, JE Abbott, LS Bingler and ES Crecelius. 2004. Long-term recovery of PCB-contaminated surface sediments at the Sangamo-Weston/Twelvemile Creek/Lake Hartwell Superfund Site. Environmental Science and Technology 38(8):2328–2337. Canadian Environmental Quality Guidelines. Environment Canada. Federal Contaminated Sites Accelerated Action Plan Annual Report 2003-2004. Federal Contaminated Sites. Government of Canada. Health effects of PCBs. U.S. Environmental Protection Agency, Sangamo Weston, Inc./Twelve-Mile Creek/Lake Hartwell PCB Contamination. Region 4 Superfund. U.S. Environmental Protection Agency. Polychlorinated biphenyls (PCBs): Basic information. U.S. Environmental Protection Agency. Polychlorinated biphenyls (PCBs): Fact sheet (PDF). U.S. Environmental Protection Agency. |
Cleaning up PCBs
