Persistent Organic Pollutants

Persistent Organic Pollutants (POPs) are an environmental and health threat to oceanic and land creatures as well as humans. They are man-made substances that are primarily carried through air and water currents. POPs settle in colder climates in the Arctic, such as Alaska where the temperatures reach below freezing. The contaminants rest there for long periods of time because the cold climate prevents them from breaking down. This is the main reason why POPs transfer from water to soil to plants onto animals and into humans.


Steller lead photo


Persistent Organic Pollutants (POPs) are an environmental and health threat to oceanic and land creatures as well as humans. They are man-made substances that are primarily carried through air and water currents. POPs settle in colder climates in the Arctic, such as Alaska where the temperatures reach below freezing. The contaminants rest there for long periods of time because the cold climate prevents them from breaking down. This is the main reason why POPs transfer from water to soil to plants onto animals and into humans.

POPs travel long distances and persist in living organisms. Several POP’s have bee show to migrate by “grasshopper effect”-repeated cycles of evaporations and condensation. They have harmful effects that interfere with the reproductive and immune systems. They also have neurological and developmental effects, especially in the brain. POPs have also been linked to cancer and are known carcinogens. POPs are a major global issue and the more recognition and accessibility to information regarding them the better (Contaminants in Alaska: Is America’s Arctic At Risk? 2000); (Toxic Burden: PCBs in Marine Life, 2002).

What are Persistent Organic Pollutants?

Persistent Organic Pollutants (POPs) are very toxic man-made organic compounds such as dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCBs). POPs are so widespread that they’re found in EVERY living organism on earth. They are by products of various industries especially paper and vinyal plastic, such as clothing, kid’s toys to medical IV bags, flooring, pipes, and siding.

The pollutants are carried by air and sea from southern areas by strong south to north winds. POPs also travel through migratory animals. Pollutants travel toward colder areas, such as Alaska, and then sink due to the colder temperature. The settled contaminants remain in the area for long periods of time because the temperature does not allow them to break down very easily. Because of this, they move from the air and water into soil and plants, then to animals and humans with ease.

The persistence in the compounds allows them to accumulate in animals and pass on more. When the pollutants progress into animals, they accumulate in the fat cells and organs and muscles while heavy metals travel exclusively toward organs and muscles. Most POPs are fat-soluble and accumulate in fatty tissues, animals in the Arctic are especially vulnerable to contamination due to the fat storage they have for the cold winters (Contaminants in Alaska, Is America’s Arctic At Risk? 2000). Due to the accumulation, the predators of the smaller organisms receive higher concentrations that move up the food web. Studies have provided evidence, that significant damage has been done to humans and animals (especially those in the early stages of life) who have been exposed to POPs. Some of the known problems directly related to POPs are reduced ability to conceive and carry offspring, a weakened immune system, reduced growth, brain damage, and they are also suspected to be carcinogens (Contaminants in Alaska, Is America’s Arctic At Risk 2000).

The POPs level found in the Arctic of Alaska is surprising to many people. This is because some pollutants have been banned from the United States and Canada for many years. The contaminants can travel far distances; most of them come from Russia, Asia, and other countries where the substances are not banned. Some POPs were used during World War II and the Cold War and still lurk in those various areas. Although they were used years ago, they are still a threat to oceanic life today (Toxic Burden: PCBs in Marine Life, 2002); (Contaminants in Alaska, Is America’s Arctic At Risk? 2000)

The Dirty Dozen

There are twelve original contaminants that make up what is known as the “Dirty Dozen”. Although there have been more contaminants discovered, the main concern is over the original twelve. These contaminants are aldrin, endrin, dieldrin, furans, hexachlorobenzene, PCBs, chlordane, DDT, dioxins, heptachlor, mirex and toxaphene. DDT and chlordane (insecticides) were commonly used to control pests in agriculture and in building materials. Dioxins and furans, are chemical byproducts, and are produced from forms of combustion, including municipal and medical waste incinerators, open burning trash and industrial processes.

What are the Dirty Dozen chemicals in?

In the Stockholm Convention on POPs, an international agreement now bans the manufacture and use of ten chemicals and restricts the release of furans and dioxins. Though there has been this international agreement, many countries, including the United States, have not ratified it, and the use of these contaminants continues. The United States has worked on removing these chemicals and the use of POPs. The contaminants have not disappeared from the environment, mainly because other countries still use them, such as Russia, and they travel the short distance from Russia’s coast to the west coast of the United States and the arctic of Alaska. Another reason is the use of PCBs in existing electrical equipment results in the contamination of air, water, and food, day after day. As a consequence, POPs can be found in our environment and our bodies. (

PCBs are the most commonly found of the contaminants in the environment. In 2001, 38 different states issued about 764 consumption advisories for fish because of PCB contamination levels. PCBs are very common in hazardous waste sites and various underwater sediments, supporting that they represent a threat to those who eat fish and the marine life.

Once POPs are released it is almost impossible to remove them from the environment, for the main reason that they have the ability to linger for long periods of time and be passed along the food web. PCBs, for example are found everywhere in the environment, although the production of them was discontinued in 1977.

PCB levels were found to be the greatest in marine animals, out of ten of the most contaminated species, nine of them are marine animals. These include dolphins, whales, and seals. These animals depend on the ocean to live; it provides them with the food needed to survive. The bottlenose dolphin is the number one most contaminated species with PCB levels of up to 2000 ppm, followed directly by the killer whale with levels up to 1000 ppm (Toxic Burden: PCBs in Marine Life, 2002).

These ten animals that are the most contaminated are known as the “Toxic Ten” and all have PCB levels that are known to cause problems in some animals. Some of the levels begin at 16.5 ppm, which is high enough to suppress the immune system. At 77 ppm, the level is high enough to begin to impair the reproductive success in some animals.

According to Canadian guidelines, nine of the ten species have high enough levels of PCBs to be considered a hazardous waste (Toxic Burden: PCBs in Marine Life, 2002).

POPs’ Effects on Fish

The nutrients necessary for plant growth (nitrogen and phosphorus) are found at very low concentrations in most natural waters. In order to obtain sufficient quantities for growth, phytoplankton must collect these chemical elements from a relatively large volume of water.

In the process of collecting nutrients, phytoplankton also collects certain human-made chemicals, such as some persistent pesticides. These may be present in the water at concentrations so low that they cannot be measured even by very sensitive instruments. The chemicals biologically accumulate in the organism and become concentrated at levels that are much higher in the living cells than in the open water. This is especially true for persistent chemicals such as DDT and PCBs that are stored in fatty tissues.

Other small fish and zooplankton eat large quantities of phytoplankton. As a result, any toxic chemicals accumulated by the phytoplankton are further concentrated in the bodies of the animals that eat them. This repeats at each step in the food chain.

The top predators at the end of a long food chain, such as lake trout, large salmon, and fish-eating gulls may accumulate concentrations of a toxic chemical high enough to cause serious deformities or death even though the concentration of the chemical in open water is very low.


From 1979 to 1995, the levels of contaminants in the peregrine falcons in interior and Arctic Alaska revealed that contaminates could be harmful to the reproductive system. Aleutian green-winged teals showed that in about 25 percent of the eggs, there were high levels of mercury that caused deformities and more than 25 percent of the eggs showed enough PCB to reduce the eggs in the laboratory from hatching; thinning of their eggshells, which made it impossible for the birds to hatch their chicks successfully, there was an early decline in birds of prey (Contaminants in Alaska, Is America’s Arctic At Risk? 2000).

Peregrine Falcons (Falco peregrines)

The Peregrine falcon is a crow-sized bird of prey that is famous for its beauty, speed, and agility. During the 1950’s, the chemical pesticide DDT and other persistent chemicals caused eggshells of peregrines and other raptors to thin. As a result, the thin-shelled eggs began to break because they were unable to support the incubating females. Because of this, peregrines disappeared from the entire eastern United States and placed on the endangered species list. As of 1999, peregrine falcons still remained on Wisconsin’s endangered species list.

Peregrine falcons and bald eagles were added to the endangered species list largely because of impact from the pesticide DDT. Understanding the food chain is important in understanding how DDT affects peregrines. The base of the pyramid represents the many birds that a peregrine falcon feeds upon each year, and lower levels that supply food for the birds such as insects and other invertebrates. DDT takes years to degrade in soil, stream, and river bottoms, so it continues to be a reproductive problem for a few birds. 

Bald Eagle (Haliaeetus leucocephalus)

In autumn, as the salmon swim upstream to spawn and die, the bald eagles gather in great numbers to feed on the exhausted and dying fish. Bald eagles also prey on other seabirds, waterfowl, mammals, and reptiles.

Pesticides such as DDT have been found in bald eagles. In the 1960’s and the use of DDT resulted in a 50-100% loss of breeding pairs in some areas; in the1990’s bald eagles showed significant signs of recovery (Contaminants in Alaska: Is America’s Arctic At Risk? 2000).

POPs’ Effect on Arctic Marine Mammals

How do these pollutants get into Alaska’s waterways? They are not used or manufactured in Alaska, yet they get into the water and then into the marine life and in some cases, progress into people. POPs are currently used in Russia, Asia and other countries. Since POPs can travel for long distances by way of air, water, and personal contact, they still have the ability to enter countries that abstain from using POPs.

Pesticides evaporate from soils and are spread around the world by winds and ocean currents. DDT levels are higher in certain areas of the Arctic than in the tropics, where most were first sprayed.

These pollutants are now being found in Alaska’s wildlife. There have been traces of pesticides, and DDT found in Aleutian Island animals such as the bald eagle, sea otters, and Steller sea lions. On Adak Island, sea otters also have concentrations of DDT that are 36 times higher than those in southeast Alaska. Other studies have shown that northern fur seal pups carried higher levels of contaminants. The higher levels of POPs were linked to a weak immune system (Toxic Burden: PCBs in Marine Life, 2002).

One way POPs have been getting into Alaska’s wildlife is through migratory animals that bring many of these contaminants from outside of Alaska. In migratory birds, the concentration of POPs has been up to 100 times higher than non-migratory birds (Contaminants in Alaska: Is America’s Arctic At Risk? 2000).

POPs are passed down to the young by the mother’s milk. The young animals are especially vulnerable to the effects of these chemicals because they render the immune system ineffective and the immune system diminishes at a rapid rate.

POPs are passed on through the food chain. It all begins with the plankton, krill, insects, and moves through the fish which eat them, on to the sea otters, sea lions, porpoises, whales, birds and many other animals. Finally, humans eat these animals and the pollutants are passed on to them. As predators acquire fat or blubber from their prey, the contaminants work their way up the food chain to the consuming animal. The highest levels of persistent contaminants are therefore found usually in the top predators.

Bowhead Whale (Balaena mysticetus)

Bowhead whales are zooplankton specialists; they prey on small to medium size copepods, euphausids, and amphipods. Tissue samples from seven bowhead whales harvested in the North Slope Borough in 1979 and 1980 have the highest level of contaminants that were found in the blubber with only traces of PCBs in the tissues of other organs (Wynne, 2003).

Northern Fur Seals (Callorhinus ursinus)

Recent studies have shown that northern fur seals have higher levels of contaminants that have been linked to the diminishing levels of their immune systems. Their diet mainly consists of schooling fish, squid, herring, capelin, pollock, and octopus. The firstborn seal pups are exposed to milk with higher concentrations of oxychlordane (OCs) than the pups of dams who have previously given birth. PCB congeners and DDT metabolites have been increasing in Northern fur seal milk leading to the continuation of PCBs entering the marine environment. (Wynne, 2003) (

Belukha Whale (Delphinapterus leucus)

Belukha Whales took number 5 in the level of PCBs with 128 parts per million. They also carry high levels of the pesticide, DDT. During summer, their diet mainly consists of fish, and at times squid and octopus. Scientists are unsure of what they eat during the winter. Researchers have found that belukha whales from eastern Chukchi Sea have slightly higher levels of PCBs and DDT in their blubber, unlike from belugas of south-central Alaska. Due to the contaminants in their diet, a decrease in the survival of their offspring has occurred (Toxic Burden: PCBs in Marine Life, 2002); (Wynne, 2003).

Sea Otters (Enhydra lutris)

In the area of the Adak Island, part of the Aleutian chain, there DDT levels up to 36 times the amount in other sea otters in southeast Alaska have been found (Contaminants in Alaska: Is America’s Arctic At Risk? 2000). Their diet mainly consists of clams, mussels, urchins, crabs, and fish. Their numbers have been increasing approximately 150,000 in Alaska waters (Wildlife Explorer, 2003).

Steller Sea Lions (Eumetopias jubatus)

Steller sea lions mainly eat fish, such as blackfish, halibut and cod. They also feed on squid, octopus, clams and crabs. Steller sea lions occasionally eat young fur seals, ringed seals and sea otter. They have been threatened and have been declining approximately to 64,000 in Alaska waters and declining at a significant rate. POPs contaminants have been found at high levels in them especially in the Aleutian Islands (Wildlife Explorer, United States of America, Dec. 6, 2003); (Contaminants in Alaska: Is America’s Arctic At Risk? 2000) (Wynne, 2003).

Killer Whales (Orcinus orca)

The transient killer whales of the North Pacific are now considered to be the most contaminated marine mammal on earth. They rank 2nd in the Oceana test for PCBs with over 1000 parts per million. Although found in all oceans, living in pods anywhere from 6 to 40 whales, many always return to the same area each year, known as “residents.” The others known as “transients”, which travel up and down the coast from year to year.

The transients whales are probably the most highly contaminated animals in the world. This is due to the marine mammal diet that includes seals and whales, which carry high concentrations of contaminants in their bodies than the fish that the resident whales eat. Contaminants in their diet have caused a decrease in the survival of their offspring. Their diet consists of marine mammals, birds, fish, squid, and turtles (Contaminants in Alaska: Is America’s Arctic At Risk? 2000).

Harbor Seal (Phoca vitulina)

Tests from Oceana rank the harbor seal 4th with PCBs at 205 part per million. Their diet mainly consists of fish, octopus, and squid. Blubber, kidney, and liver samples were taken from twenty-three harbor seals in the Kodiak Archipelago in the Gulf of Alaska. Test showed that PCBs and the pesticides DDT, DDE, and OCs were detected. PCBs showed up in 21 of 22 blubber samples taken, there was no difference in the concentrations between the males and females. Instead, DDT was significantly higher in males than in females and it was found in 68% of the seals. DDE was found in all the samples taken and OCs was found in 55% of the samples. In both, DDE and OCs the males contain higher amounts than the females (Toxic Burden: PCBs in Marine Life, 2002).

Polar Bear (Ursus maritimus)

Tests have shown that male polar bears from Alaska carry one of the highest concentrations of hexachlorobenzene (HCH, a pesticide) and rank 9th in the Oceana test for PCBs in the Arctic at 80 part per million. The polar bear is one of the top predators and of the marine food chain. There is a high death rate in polar bear cubs, possibly due to high levels of organochlorines (Toxic Burden: PCBs in Marine Life, 2002) Abnormally formed genitalia were found in four polar bears possibly due to exposure to high levels of PCBs in the womb. They rank high in both HCH and PCB due to their diet that consists of mainly seals. They eat primarily ringed and bearded seals; occasionally polar bears eat other mammals, eggs, and vegetation (“Toxic Burden” PCBs in Marine Life, Oceana, page 10); (Wynne, 2003).

Protecting Alaska’s Whales

Pesticides from agricultural run-off and industrial pollutants from dumping affect whales in Alaska. Plankton takes up these pollutants that become increasingly concentrated and as they pass up through the food chain. When the whales ingest the plankton, the toxins cause damage to the whale’s organs and reproductive and nervous systems (Wildlife Explorer, Dec. 6, 2003).

Protecting Alaska’s Sea Otters

When western farmers began using pesticides, including DDT in the 1950’s, the chemicals from the pesticides found their way into the watercourses in which the sea otters lived, traveled, and fed. By the 1960’s, scientists revealed that 80% of the otters had lethal levels of toxic chemicals in their liver.

More recently the sea otter population has been increasing about 5% a year and there have been calls for resuming the annual otter fur harvest. (Wildlife Explorer, Dec. 6, 2003,).

The Ways in Which People are Affected

Not only are contaminants, such as POPs found in living organisms as animals and plants, but also in humans. Both adult Inuits and Alaskan Natives have been studied and have elevated body burdens of POPs such as PCBs and DDT. POPs tend to magnify in higher living organisms such as humans, so their presence in humans is not surprising.

Although the POPs and heavy metal levels in the Arctic, which humans are exposed are considerably low, there is still concern because exposure of these pollutants at a young age can have serious consequences such as any of the following:

  • birth defects
  • certain cancers
  • immune system disorders
  • reproductive problems
  • reduced ability to conceive and carry offspring
  • decreased ability to ward off disease
  • stunted growth and permanent impairment of brain function
  • POPs are a suspected carcinogen

Human exposure to POPs is carried through the food chain. Because the animals are subsisting in water contaminated with these pollutants, they are affected as well. When the humans consume these animals, they have also consumed the pollutant, which then is accumulated the body.

It is primarily the native people who are affected by POPs because it is a part of their culture to live off the land by hunting and fishing. This way of life is essential and unique for each tribe.

The people in the north tend to consume more meats and fats than people in the south. In turn, the people in the north have a greater risk of exposure to POPs because they concentrate in living organisms 70,000 times the levels detected in soil or water (Contaminants in Alaska: Is America’s Arctic at Risk? 2000).

Due to the low levels of POPs found in humans, there has not been a panic to abruptly alter the native’s diet. Although a concern, the current POPs levels are not significant enough to outweigh the benefits of a subsistence diet. The foods currently consumed by natives comprise the basic nutrients required on a day-to-day basis and also have tremendous health benefits.

Because children are still developing, they are much more susceptible to the effects of pollutants. Their developing cells are sensitive to contaminants and are more likely to be affected by exposure of POPs. The brain is apparently in the greatest concern because studies have shown that children exposed to POPs during infancy had remarkably lower scores on assessments determining intelligence and ability to shut out distractions.

The detection of POPs in humans is fairly recent so there is not much that is known on the subject. Since the dosages of contaminants found in humans are so minuscule, results are hard to validate (Toxic Burden: PCBs in Marine Life, 2002); (Contaminants in Alaska: Is America’s Arctic At Risk? 2000)


There are many risks and effects of having these chemicals in our environment, and none of them are a benefit to the earth. After these pollutants are put into the environment, they are able to stay in the system for decades, causing problems such as, cancer, birth defects, learning disabilities, immunological, behavioral, neurological, and reproductive discrepancies, in humans and other animal species. Because they cause these deformities, and reproductive failures, the wildlife population begins to decline.

PCBs, chemicals that have once been used as lubricants and coolants in electrical equipment, have now been connected with problems with the nervous, immune, and hormonal systems. They have also been considered a cancer-causing agent by the U.S. Environmental Protection Agency ( 2003).

Because the levels of these PCBs and other POPs are present in most waterways, the risk of consuming fish and other wildlife that come from these waters is great on human and other animal species that may rely on the resources from the water for their diet. In the Great Lakes, most fish exceed the level of 0.094 ppm, which is the level that the EPA has established an advisory in recommending against the consumption of certain fish. In consuming these fish by humans or other animal species, the effects that it could lead to the toxic effects and contribute to the high level of PCBs in the consumers. The effects on wildlife are great. In the arctic of Alaska, the levels of the contaminants pose a threat to some animal populations’ resistance to infection, reproduction, and behavior, not only to the survival and reproductive success to individual animals, but threatening the whole population.

A broad attack on reproduction

One of the causes of failure to reproduce is that some of the chemicals interfere with sex hormones. These hormone disrupters can mimic or block contaminants that block the estrogen receptor may inhibit growth of the reproductive tract and mammary glands. In fish, the same receptor stimulates the production of a precursor to egg yolk.

Sex hormones are significant to the development of normal sexual organs of young animals. In polluted, temperate environments, high levels of hormone disrupters have been blamed for the malformations in reproductive organs change of sex, and abnormal mating behavior.

The immune system is very sensitive

The immune system may be the most sensitive targets for these contaminants. The thymus, which normally produces antibodies to fight infectious agents, can disintegrate away and stop functioning. There are signs that animals with high loads of organic contaminants are more susceptible to infections. POPs limit cell-mediated immunity, the branch of the immune system that fights cancer cells and parasites.

Liver enzymes are telltale signs of intoxication

Within the body, toxic chemicals may be converted into less toxic substances that can be excreted. The liver is where most of this detoxification and many organic contaminants start the production of specific liver detoxification enzymes. Measurements of these enzymes are now used as biological indicators of the load of contaminants in an animal. These same enzymes are also able to break down hormones. These side effects of detoxifying high levels of contaminants can increase the breakdown of hormones and impair critical hormone-dependent functions, such as reproduction.

Increased risk of tumors

Many of the POPs are suspected of being responsible for the increased rates of tumors in the polluted wildlife habitats. There are two ways by which a contaminant can increase the risk of cancer. One is the mutation of hereditary material in cells, the DNA, which makes the cell lose control of it growth. The second allows a cell damaged in this way to turn into a tumor. Contaminants implicated in the latter process are called promoters, and this group includes most of the POPs. They do not cause cancer by themselves, but can act together with DNA-damaging chemicals.


POPs can disturb the production of the pigment in red blood cells; in severe cases can lead to the disease porphyria. Some symptoms may include skin damage after exposure to sunlight as well as damage to the nervous system. The biochemical changes associated with porphyria, are measurable long before symptoms appear, may be used as sensitive biological markers of POPs in the environment.


POPs are highly toxic chemicals, and are a very dangerous part of our environment. If something is not done to decrease the amount of these pollutants soon, our wildlife and the habitat itself will suffer in the long run.

It is understandable that it may be impossible to rid the environment of these pollutants; but by realizing what the risks of using them in our everyday life, perhaps others will be more welcome to the ban that came about in the Stockholm Convention, a global treaty banning POPs. Because POPs are able to travel long distances and stay in the environment for decades at a time, banning them only in some countries is not good enough (Toxic Burden: PCBs in Marine Life, 2002). POPs are not used or manufactured in Alaska, yet they have been causing problems in its environment, because counties like Russia still use them and POPs come through the rivers and into the ocean flowing toward Alaska.

POPs are made up of twelve pollutants that are common in our every day life. The most common form of them are the pesticides and insecticides, and along with PCB man-made materials such as, electrical, heating transfer, and hydraulic equipment. (

These then pollute our water, air and food supply and get into our bodies and cause major problems such as cancer, reproductive disorders, disruption of the immune system and interference with the development of the young (Contaminants in Alaska: Is America’s Arctic at Risk? 2000).

In order to decrease the risk of POPs, we need to rapidly phase out these pollutants, or else the environment is going to be concentrated with levels of POPs that can ultimately cause death of humans and other animal species.


Figure 1.


This image shows how POPs migrate around the world. 

Figure 2.

Fig. 2, arctic marine food chain

Arctic Marine Food Web 

Figure 3.

Fig. 3

Figure 4.

Fig. 4

PCB (red) and DDT (blue) in polar bear in different Arctic regions, measured ng/g blubber. 

Table 1.













This table shows the original twelve Persistent Organic Pollutants. “The Dirty Dozen.” (Toxic Burden: PCBs in Marine Life, 2002.)

Table 2.

The Dirty Dozen


Industrial Products/equipment

Chemical Byproducts

















































This graph shows what the contaminants are most commonly used in and come from. The shaded regions represent what sections the contaminants are contained in with. 1.) Pesticides, 2.) Industrial Products/Equipment, and 3.) Chemical Byproduct. 


  1. Ayres, Jak., McLachkan, Dan H. Fieldbook of Pacific Northwest Sea Creatures. Happy Camp, California: Naturegraph Publishers, Inc., 1979.
  2. Boesch, Donald F., Burroughs, Richard H., Baker, Joel E., Mason, Robert P., Rowe, Christopher L., Siefert, Ronald L. Marine Pollution in the United States. Arlington, Virginia: Pew Oceanus Commission, 2001.
  3. Carefoot, Thomas. Pacific Seashores. United States of America: University of Washington Press, 1977.
  4. Carelton University School of Journalism and Communication. Where POPs are from. (Nov. 24, 2003).
  5. Circumpolar Conservation Union. POPs in Alaska. 20, 2003).
  6. Contaminants in Alaska: Is America’s Arctic At Risk? Interagency Collaborative paper: September, 2000.
  7. Inuit Tapiriit Kanatami Environment Department. Persistence of POPs in fat. (Nov. 28, 2003).
  8. International Masters Publishers, Wildlife Explorer (Dec. 11, 2003)
  9. National Oceanic and Atmospheric Administration (NOAA). POPs in Alaska. (Nov. 18, 2003).
  10. Oceana. Toxic Burden: PCBs in Marine Life. Washington DC: 2003.
  11. Pan Ap. POPs toxicity and effects. (Nov. 20, 2003).
  12. Pesticide Action Network UK. POPs in Polar Bears. (Nov. 28, 2003).
  13. Persistent Organic Pollutants (POPs) in Alaska: What Does Science Tell Us? (Nov. 24, 2003)
  14. Rudolph, S. Alaska Community Action on Toxics. Redlands, California: March 15, 1999.
  15. Stockholm Environment Institute. How POPs travel. (Nov. 24, 2003).
  16. Wynne, Kate Guide to Marine Mammals of Alaska University of Alaska Fairbanks: 2003

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Persistent Organic Pollutants

Persistent Organic Pollutants (POPs) are an environmental and health threat to oceanic and land creatures as well as humans. They are man-made substances that are primarily carried through air and water currents. POPs settle in colder climates in the Arctic, such as Alaska where the temperatures reach below freezing. The contaminants rest there for long periods of time because the cold climate prevents them from breaking down. This is the main reason why POPs transfer from water to soil to plants onto animals and into humans.

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