hexachlorocy
polybrominated diphenyl
PolyChlorin
Tox
Chlordane
Tributyltin
STAFFANWIDSTRAND
Persistent Organic Pollutants
Stiff and lean after six months curled in a den, a female polar bear squeezes herself out of her winter home. Two small
cubs emerge tentatively at her heel for their first view of the world beyond a snow cave. Entirely dependent on their
mother, the cubs follow obediently. Having used up most of her fat stores, the female scans the sea ice below and ponders
a meal of seal blubber. But her cubs are not yet ready to travel, and her milk will have to sustain them for some time to
come. The milk is rich and nourishing but today it also harbors a threat. The seals the mother has feasted on in the past,
and will need again soon, are tainted by chemicals from lands far beyond her sea-ice domain. The chemicals that bind to
the fat of the seals have accumulated in her own fat stores. Unwittingly, the mother passes the toxins to her young in her
fat-rich milk, with effects that are still unclear.
This chapter examines organic chemicals that can affect the health of animals and people, especially those substances
that accumulate in Arctic food webs and that resist degradation. These are often called persistent organic pollutants, or
POPs. A review of known toxic effects and environmental levels of POPs forms the basis for evaluating whether Arctic
wildlife are affected by current levels of contamination. A summary of sources and pathways indicates where the contaminants
come from. Many measurements of organic contaminants have been made because of concern about high intake
by people, and the human health aspects of these substances are discussed in the chapter Pollution and Human Health.
yclohexane
ethers
nated Biphenyls
xaphene
furans
Persistent organic pollutants:
a background
In 1945, the booming chemical industry
launched a new, effective tool for dealing with
insect pests: DDT. It held great promise,
including the hope of saving crops and of eradicating
disease-carrying insects. Twenty years
later, DDT and other, similar chemicals had
indeed benefited agriculture and relieved some
of the problems associated with insects in
many areas of the world. The price of these
gains, however, was becoming increasingly
clear: DDT is toxic to many more organisms
than those it was intended to kill. In particular,
birds of prey had trouble reproducing, and
their populations declined in many polluted
areas of the world.
As early as 1970, when it was detected in
the blubber of ringed seals, it was evident that
DDT was present in the Arctic. By the mid-
1970s, researchers had documented the presence
of DDT and other pesticides in beluga,
polar bear, and fish. Moreover, birds of prey
declined in northern areas that were thought
to be uncontaminated.
In addition to pesticides, most analyses in
animals also found traces of an industrial oil
made of compounds known as PCBs. By 1980,
there was evidence that some of these contaminants
had reached the Arctic via long-range
transport. In the late 1980s, it became clear
that human mother’s milk at Broughton Island
in the Northwest Territories in Canada contained
enough PCBs to cause concern about
effects on human health. The most likely
source was the food the women had eaten.
DDT and a number of closely-related pesticides
have been banned for two decades in the
circumpolar countries, but long-range transport
makes the issue a global one. While PCBs
are no longer manufactured in any of the circumpolar
countries, they are still in use in
many closed systems, and leaks and disposal of
old stores remain a problem. New chemicals,
with unknown effects on Arctic animals, are
also entering the scene.
The biological effects
of POPs
Organic contaminants in the Arctic environment
share many characteristics that make them
especially insidious for people and wildlife.
POPs are stored in fat and are persistent
A common characteristic of most synthetic
organic chemicals found in Arctic animals is
that they break down very slowly. This persistence
in the environment allows them to accumulate
in animals, and to pass through the
food web.
Most of the persistent organic pollutants are
also fat-soluble. They thus accumulate in the
fatty tissues of animals. Storing energy as fat is
crucial for survival in cold environments, and
fat is therefore important in the diets of both
people and animals, which also increases the
intake of these pollutants.
The combined characteristics of being fatsoluble
and persistent make biomagnification a
major concern. Biomagnification is the
increase in contaminant load as predators take
on the chemicals eaten by their prey, thus further
concentrating the toxic material at each
successive level of the food web. For a detailed
discussion of this process, see the chapter
Polar Ecology. Indeed, the highest levels of
persistent contaminants are usually found in
top predators. Studies of species at different
levels of an Arctic marine food web show that
each step can mean a several-fold increase in
body burdens of organic contaminants.
A broad attack on reproduction
Many of the most visible effects of POPs on
animals are related to the ability to conceive
and raise young. For example, the early declines
in birds of prey were caused by thinning
of their eggshells, which made it impossible for
the birds to hatch their chicks successfully.
POPs may also be directly toxic to developing
chicks, killing them in the egg. A more subtle
effect is seen in adult birds, when normal mating
behavior is impaired.
The effects of POPs on mammals are well
documented in polluted areas such as the
Baltic Sea. Malformations in reproductive
organs, fewer young, or even complete failure
to reproduce are some of the detrimental signs
of high contaminant levels.
One of the underlying causes of failure to
reproduce is that some of the chemicals interfere
with sex hormones. Such hormone disrupters
can mimic or block hormones because
they are similar enough in structure to fit into
the body’s biochemical receptors.
Contaminants that block the estrogen receptor
can inhibit the growth of the reproductive
tract and the mammary glands, which mammals
require to maintain pregnancy. In fish,
the same receptor stimulates the production of
a precursor to egg yolk. Under normal conditions,
the yolk precursor is only present in
females, but in contaminated waters it is also
found in males. Some of these measurable biological
effects are now used as sensitive tests to
determine whether a specific compound is a
hormone disrupter.
Sex hormones are important for the normal
sexual development of young animals. In polluted
temperate environments, high levels of
hormone disrupters have been connected to
malformations in reproductive organs, change
of sex in some species, and abnormal mating
behavior.
72
Persistent Organic
Pollutants
The immune system is very sensitive
One of the most sensitive targets for organic
contaminants may be the immune system, the
body’s primary defense against disease. The
thymus, which normally produces antibodies
to fight infectious agents, can waste away and
cease to function. POPs also limit cell-mediated
immunity, the branch of the immune system
that fights cancer cells and parasites. There
are signs that animals with a high load of contaminants
are more susceptible to infections.
Liver enzymes are tell-tale signs
of intoxication
In the body, many toxic chemicals are converted
into less toxic substances that can be excreted
in urine or feces. The liver does most of
this detoxification, and many organic contaminants
stimulate 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.
Stimulating the detoxification enzymes is
not a problem in and of itself. However, the
same enzymes are also responsible for breaking
down hormones. Therefore, contaminants
can indirectly increase the breakdown of hormones,
potentially influencing critical hormonedependent
functions, such as reproduction.
The liver-enzyme systems are different in
different species, which affects their respective
abilities to process contaminants. This can
explain why some animals can get rid of a specific
substance, while other animals accumulate
it. Fish completely lack one of these
enzyme systems, which makes them a carrier
of many POPs in the food web.
Increased risk of tumors
Several POPs are suspected of being responsible
for increased rates of tumors in wildlife in
polluted areas. There are two ways by which a
contaminant can increase the risk of cancer.
The first is a mutation of hereditary material in
the cells, the DNA, which makes the cell lose
control of its 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 POPs. They do not cause cancer by themselves,
but can act together with DNA-damaging
chemicals.
Sensitive glands and vitamin A
Several hormone-producing glands in the body
are sensitive to POPs. One is the thyroid,
which is responsible for the balance of thyroid
hormones. A chemical disruption of the thyroid
can lead to goiter and to changes in metabolism
that affect growth and reproduction.
Some POPs may affect the breakdown of
Vitamin A. Imbalance in Vitamin A can suppress
the immune system, increase susceptibility
to cancer, cause skin lesions, and disrupt
reproduction, growth, and development.
Many POPs can damage the adrenal gland.
Seals in the Baltic Sea suffer from a series of
diseases that are connected to adrenal gland
effects. These diseases include malformations
of the uterus, which is one of the reasons
Baltic seals have had trouble reproducing.
Porphyria
Some POPs disturb production of the pigment
in red blood cells, which in severe cases leads
to the disease porphyria. Symptoms include
skin damage after exposure to light as well as
damage to the nervous system. The biochemical
changes associated with porphyria, which
are measurable long before symptoms appear,
are used as sensitive biological markers of
POPs in the environment.
Effect assessments
include many uncertainties
Most of our knowledge about the toxicology
of organic pollutants comes from studies with
laboratory animals, semi-field studies with a
few species of wild animals, and studies of the
association between contaminant levels and
effects in wild animals. This includes information
about what levels of specific contaminants
can potentially be associated with health
effects in the animals. The assessments presented
later in this chapter therefore include
many uncertainties. For example, the assessments
assume that Arctic animals in their natural
environment have approximately the
same sensitivity as the animals that were used
in the toxicological studies. In reality, they
could be more sensitive or less so. Thus, when
POP levels in Arctic biota reach biological
effects thresholds determined from other animals,
it should be interpreted as a warning signal
rather than as evidence that such effects
actually do occur in the Arctic.
73
Persistent Organic
Pollutants
The peregrine falcon is
a bird of prey that has
been hard hit by persistent
organic contami-
nants.
STAFFANWIDSTRAND
A cast of characters
The term ‘organic contaminants’ covers a wide
range of substances. Some are industrial chemicals
whose toxic character is unintentional.
Others are byproducts in industrial processes.
The third category includes substances that are
designed to be toxic, such as pesticides. Many
organic contaminants contain chlorine and are
also called organochlorines. Most organochlorines
discussed in this chapter have no natural
sources in the environment.
Industrial chemicals and byproducts
PCBs
The term ‘PCBs’ refers to a group of chemicals
called polychlorinated biphenyls. They were
introduced in 1929 and manufactured in the
United States, Japan, the former Soviet Union,
and eastern and western Europe. They are
chemically stable and heat-resistant, and were
used world-wide as transformer and capacitor
oils, hydraulic and heat-exchange fluids, lubricating
and cutting oils, and as plasticizer in
joint sealants. Open use is currently banned in
all circumpolar countries, but there are still
substantial amounts in large capacitors and
transformers. Current use and disposal are
often poorly documented.
The toxic effects of PCBs depend on their
chemical structure. The most toxic PCBs have
a coplanar configuration, which is similar to
dioxins (see next subsection). PCBs have a
range of toxic effects. The most significant of
these may be that they suppress the immune
system, making animals more likely to become
ill and more likely to die if they are exposed
to infections. They can also disturb behavior
and reproduction in birds, fish, and mammals.
PCBs have contributed to population declines
and health problems in fish-eating mammals
in polluted areas, including the beluga in the
St. Lawrence River estuary, seals in the Baltic
Sea, and European otters. The reduced number
of fish-eating birds in the Great Lakes
region has also been associated with high concentrations
of PCBs, especially the dioxin-like
coplanar PCBs.
Other sensitive targets for the toxic effects
of PCBs include the developing nervous system
and liver enzymes. PCBs can also act as a cancer
promoter and can cause birth defects.
Dioxins and furans
Dioxins (PCDDs) and furans (PCDFs) are a
group of chlorinated chemicals, of which 17
are toxic in minute quantities. They are primarily
created in high-temperature processes.
Waste incinerators without efficient flue-gas
cleaning systems are or have been one of the
most significant sources. Wood-burning stoves
and the use of leaded fuel add to the load in
the atmosphere. Dioxins and furans also enter
the environment as byproducts of industrial
processes. Metallurgical industries are large
sources to the air, while pulp and paper mills
that use chlorine in the bleaching process often
release contaminated water. A third type of
source is as trace contaminants in chlorophenoxy
acid herbicides (e.g. Agent Orange), in
chlorophenol wood preservatives, and in PCB
mixtures (mainly furans).
The toxic mechanism for dioxins and furans
is the same as for the coplanar PCBs, but some
are considerably more potent. Effects include
disturbed reproduction, a suppressed immune
system, and an increased risk of cancer.
Hexachlorobenzene
Hexachlorobenzene (HCB) is a byproduct in
the production of chlorine gas and chlorinated
compounds, including several pesticides. It is
emitted to the atmosphere in the flue gas from
waste incineration, and is also formed by metallurgical
processes. It has had limited use as a
pesticide. The major concerns are porphyria
and effects on reproduction and on the
immune system.
Brominated flame retardants
Many substances that are used as flame retardants
have chemical properties that are similar
to PCBs. Polybrominated diphenyl ethers can
leach out of flame-retardant-treated textiles,
electrical equipment, building material, and car
interiors to cause diffuse contamination of the
environment. Knowledge about the toxicity of
brominated flame retardants is very limited.
Pesticides
Many of the pesticides found in animals are
organic compounds that have several chlorine
atoms and are very persistent in the environment.
Pesticides are designed to be toxic to
their target organisms. Most of them affect the
nervous system and the liver, and several interfere
with reproduction.
DDT
DDT is a chlorinated organic pesticide, introduced
as an insecticide in 1945. Circumpolar
countries restricted its use two decades ago,
but it is still used in pest control programs in
southern Asia, Africa, Central and South America,
and Europe (e.g. Italy). In the past, it has
been used to control mosquitoes and black flies
in the Arctic, and there may still be some use
in remote areas of Siberia, in spite of bans. In
Russia, household and institutional insecticides
that contain DDT and hexachlorocyclohexane
are still in use. DDT enters the region via air
and water currents and in migratory animals.
In the environment, DDT is converted to
the metabolites DDE and DDD. These are
stored in fatty tissues of fish, birds, and mammals.
It is the cause of eggshell thinning in
birds. DDT and its metabolites also disrupt sex
hormones and affect liver enzymes.
74
Persistent Organic
Pollutants
Toxaphene
Toxaphene is a complex mixture of polychlorinated
bornanes and camphenes. Until the early
1980s it was widely used to fight insects in cotton
crops in the United States. Manufacture
and use are now banned in the United States,
but similar products are still used in some
parts of the world, including Mexico and
Central America.
It is difficult to measure toxaphene in the
environment. The levels in the Arctic are therefore
not well studied, despite the fact that
toxaphene has been recognized as a persistent
organic pollutant of great concern. It may be
one of the most abundant pesticides in Arctic
wildlife, but limited exposure information and
lack of data on toxicological effects make risk
assessments difficult.
Toxaphene’s major toxic effects are on the
nervous system. Fish are extremely sensitive,
becoming hyperactive with muscular spasms
and losing their equilibrium. In experiments,
fish that have been injected with toxaphene at
levels measured in the environment and then
released into the wild have lower survival rates
than uncontaminated fish.
Chlordane
Chlordane is a mixture of compounds that has
been used to protect seeds from insects and for
termite control. It is no longer used in most
circumpolar countries, but is still produced for
export in the United States. One of the components
of chlordane (heptachlor) breaks down
to a compound (heptachlor epoxide) that is
carcinogenic, and has been found in the Arctic
environment. Oxychlordane is another toxic
metabolite. Chlordane affects reproduction
and the immune system.
Hexachlorocyclohexane/lindane
Hexachlorocyclohexane (HCH) has a number
of isomers, of which alpha, beta, and gamma
are usually those found in environmental samples.
The gamma isomer, also called lindane, is
the most potent as an insecticide. Lindane is
still used in North America, Japan, and Europe
to treat seed and in Europe for other purposes.
Other forms of the compound were banned in
the late 1970s. In China and some other countries,
technical mixtures of different hexachlorocyclohexanes
are still used to treat hardwood
logs and lumber, seeds, vegetables and fruit,
and buildings. Lindane is a neurotoxin. It also
adversely affects reproduction, the liver, and
the immune system, and is a cancer promoter.
Dieldrin
Dieldrin is a soil insecticide. It is no longer
used in circumpolar countries. Manufacture in
Europe, especially for export to developing
countries, continued until the late 1980s. Dieldrin
is extremely persistent in soil and in biota.
It is the strongest carcinogen of the organochlorine
pesticides.
Mirex
Mirex was used as an insecticide and fire retardant,
mainly in the United States and Canada,
until 1978. Mirex is highly fat-soluble and persistent
in the environment. It is implicated in
cancer and reproductive effects seen in laboratory
animals.
Organotins
Tributyltin (TBT) is an organic compound
containing the metal tin. It is used as a broadspectrum
killer of algae, fungi, insects, and
mites. Since the 1960s, TBT has mainly been
used as a marine antifouling agent. It leaches
into the water from surface coatings on boats,
aquaculture pens, moorings, and industrial
cooling pipes. Other sources are boat repair
yards, marinas, and municipal wastewater and
sewage sludge. Several countries have banned
the use of TBT for small boats, but international
regulations still allow restricted use.
TBT breaks down rapidly at the sea surface,
with a half-life of only a few days. However, in
sediments and especially under cold conditions,
it can remain for much longer, with a
half-life of over two years. Sediment can thus
remain a source long after any bans on the use
of TBT have taken effect.
TBT is one of the most toxic substances that
has been introduced to natural waters. A few
nanograms per liter are enough to affect dogwhelk
snails. Chronic effects in oysters, mussels,
and crustaceans are observed at exposure
levels of less than 1 microgram per liter. It is
moderately fat-soluble and can thus bioaccumulate.
It is a hormone disrupter that affects
reproduction.
Less persistent pesticides
A large number of chlorinated pesticides are
still used in circumpolar countries and elsewhere
in the world. These are less persistent
than their predecessors and do not accumulate
or biomagnify to any great extent. Most
of them have short half-lives in water, soil,
and sediment. Nevertheless, many of these
compounds have been found in the Arctic,
especially in air, seawater, and sea ice. This
reflects both their large-scale use – in some
cases over a million kilograms per year – and
their transport by winds in a manner similar
to many of the banned pesticides. Little is
known about whether low light and low
temperatures may make them more persistent
in the polar environment than in temperate
climates.
Examples of currently used chlorinated pesticides
that have been found in air, lakewater,
fish, seawater, snow, and plants in the Arctic
are atrazine, endosulfan, chlorpyrifos, chlorothalonil,
tetra- and pentachlorophenol, and
methoxychlor. Non-chlorinated pesticides include
the organophosphate terbufos, the
phenylamide herbicide metolachlor, and the
dinitroaniline herbicide trifluralin.
75
Persistent Organic
Pollutants
Sources and pathways
The picture of sources and movements of
POPs to the Arctic is complex. Most POPs do
not move directly from their source to their
destination, but cycle around in the global
environment as was described for multi-hop
compounds in the chapter Physical Pathways
of Contaminants Transport. The box below
gives a further explanation of some of the
peculiarities of these contaminants.
Global pool of contaminants
is the major source
The major source of most persistent organic
chemicals to the Arctic today is the residue of
widespread contamination of the global environment,
the sum of past uses; see table below.
Modeling the pathways and transport of
POPs gives an indication of how long this global
source will continue to contaminate the Arctic
environment. Such a model for DDT shows
that it will be with us for many decades more.
After a complete global ban, about 10 percent
of the atmospheric load, 30 percent of the soil
load, and only 1-2 percent of the ocean load will
disappear each decade. Such models are still in
their infancy, but nevertheless provide an indication
of potential future environmental burdens.
The models also show that the propensity of
different compounds to reach the Arctic via
the atmosphere differs with their chemical
characteristics. Some, such as hexachlorocyclohexane,
are more likely to travel all the
way, whereas others, such as dioxins, only
reach the far north to a limited extent. In general,
only part of the global burden will reach
the Arctic, but this fraction can still create significant
problems because of the tendency of
organochlorine contaminants to concentrate in
the fat of Arctic animals and biomagnify in the
food web. This can lead to high levels in toplevel
predators, including people. Cold temperatures
in the Arctic also seem to create a sink
for certain persistent organic pollutants, which
may in some cases result in POP levels that are
higher in the Arctic than in the source regions.
This phenomenon is often referred to as the
cold-condensation effect.
Some pesticides
are still produced and used
The concern about long-range transport of
POPs has led to several political initiatives to
limit the production and use of these chemicals.
To some extent these efforts have been
successful, but it is difficult to get an accurate
picture of the current global situation. International
statistics are lacking and some industries
are reluctant to release production numbers.
An inventory made by the Governing Council
of the United Nations Environment Programme,
as part of a Global Action Plan, shows that
DDT is still produced to control disease-carrying
insects, and that it is also misused for other
purposes. Chlordane is still produced for ant
and termite control, while production of
aldrin, dieldrin, and endrin has stopped. Mirex
also appears to be out of production, as does
hexachlorobenzene for use as a pesticide.
The table below gives a picture of where the
pesticide hexachlorocyclohexane is still used
including lindane, which is still produced and
used in Europe. Available data suggest that
76
Persistent Organic
Pollutants
A global flux among particles, water, and air
The transport and fate of organic contaminants depend to a large extent on the physical-chemical
properties of each chemical. One of the key characteristics is the environment
that a particular molecule prefers. A few compounds are slightly soluble in
water, with hexachlorocyclohexane as a prime example. However, most organic contaminants
have an affinity for particles and fatty matrices. Depending on temperature,
some of the molecules will favor the gas phase.
There is an equilibrium between these abiotic phases, so that some of each contaminant
is in the air, some in the water, and some is associated with particles. Changes in
temperature can alter the equilibrium, and contaminants will move from one phase to
another. For example, if the temperature rises, POPs from the soil, from the snow
pack, or from the surface water of the ocean will move into the atmosphere. The
break-up of ice in the spring also allows for exchange between water and air. Meltwater
washing over the ground and winds picking up dirt are physical processes that
can move the contaminants.
During the cold winter months, most POPs adhere to particles. In the atmosphere,
they get carried to the Arctic on haze aerosols that follow major wind currents. In
summer, when the air warms to 0°C or more, some contaminants will be transported
as gases.
The further fate of the particles will depend on when snow and rain clean the air,
whether contaminants become fixed in the soil or washed away by snowmelt, and
whether contaminant-laden sediment particles end up in rivers that reach the sea.
Usage of selected pesticides for various periods of time.
––––––––––––––––––––––––––––––––––––––––––––––––––
Pesticide Usage, tonnes Period
––––––––––––––––––––––––––––––––––––––––––––––––––
Accounted for
DDT 1500 000 1948-1993
Technical HCH 550 000 1948-1993
40 000 1980
29 000 1990
Technical lindane 720 000 1948-1993
5 900 1980
4 000 1990
alpha-HCH 28 000 1980
20 400 1990
gamma-HCH 11 900 1980
8 400 1990
Toxaphene 450 000 1948-1993
Interpolated
DDT 2600 000 1950-1993
990 000 1970-1993
Toxaphene 1330 000 1950-1993
670 000 1970-1993
––––––––––––––––––––––––––––––––––––––––––––––––––
Estimated annual usage of alpha-HCH and gamma-HCH
in 1990 for the top-consuming countries.
––––––––––––––––––––––––––––––––––––––––––––––––––
Country Usage, tonnes
––––––––––––––––––––––––––––––––––––––––––––––––––
alpha-HCH
India 19 880
Mexico 183
Ukraine 168
gamma-HCH
India 4 260
France 1 860
Italy 600
Nigeria 397
Canada 150
United States 114
China 100
Spain 96
––––––––––––––––––––––––––––––––––––––––––––––––––
India is the major user of lindane and technical
hexachlorocyclohexane. Other countries may
also be significant sources.
Pesticides have been used
for insect control in the Arctic
Pesticide use in the Arctic has mainly been for
insect control, which has probably occurred in
all circumpolar countries. There is, for example,
anecdotal evidence of spraying around
military installations.
In the Yukon Territory of Canada, the use
of pesticides has been well documented. Starting
in 1948, DDT was applied directly into the
Yukon River to control mosquitoes and black
flies. Several other organochlorine pesticides
were also tested. Starting in 1949, the Canadian
air force sprayed DDT mixed with fuel oil
around its bases at Whitehorse and at Watson
Lake. In 1964, ground fogging and the use of
capsules of DDT and lindane replaced aerial
spraying. However, as a result of pressure
from local populations, the aerial spraying of
DDT was resumed and continued until 1969,
when DDT was replaced by other insecticides.
Drums with leftover DDT have been dumped
at community landfills and on the shore of the
Yukon River.
DDT was probably used for insect control
around military sites in Alaska as well. In remote
areas of Siberia, there may still be some
use of DDT for insect control, in spite of bans.
As far as can be determined, no organochlorine
pesticides have been used in Arctic Norway
or Sweden.
PCBs are still around
in buildings and landfills
Several compounds that are no longer manufactured
are nevertheless important when considering
the sources of Arctic contamination.
To identify environmental problems that must
be dealt with in order to minimize future emissions,
AMAP has tried to make a qualitative survey
of sources within the circumpolar countries.
PCB mixtures have been banned from open
use in all circumpolar countries, but in some
countries are still allowed in closed systems
that existed prior to the ban. Unintentional
open use still occurs. For example, in Norway
650 tonnes are contained in products that are
still around, mostly window sealing compounds
and lighting equipment. Also, 400 to 600 tonnes
of technical PCBs have been disposed of in
such a way that they may eventually be released
into the environment. This situation is probably
not unique to Norway.
Several products used in buildings are leaking
PCBs into the environment. In Sweden,
joint sealant that was used in connecting prefabricated
building elements from 1950 to
1972 contains up to 20 percent PCBs as plasticizer.
This is the equivalent of 100 to 500 tonnes
of PCBs in unintended open use in Sweden.
Elevated levels of PCBs in the air and soil outside
these buildings have been documented.
Some of the PCBs have probably ended up in
landfills. The joint sealant was marketed internationally
and used in other countries as well.
Other sources of PCBs in old buildings are
floor paints.
Abandoned military sites
are local PCB sources
Prior to the mid-to-late 1970s, PCBs were
widely used in transformers, capacitors, and
other electrical equipment. Leaks or improper
disposal are known from the past, occurring,
for example, at military radar stations.
In Canada, this use and the consequent local
contamination have been well documented in a
study of Distant Early Warning (DEW) Line
Sites built to detect missiles and bombers heading
toward North America. The DEW Line
consisted of 63 stations across Alaska, Canada,
and Greenland, roughly following the 66th
parallel. At the time the stations were in use,
no one was concerned about dumping PCB fluids
in the environment. Of an estimated 30
tonnes of PCBs used in the stations, an unknown
amount has ended up in their landfills.
Environment Canada and the Canadian Department
of National Defense have attempted
to clean up some of the stations by taking care
of waste-containing drums, old equipment,
and contaminated soil. However, many sites
are still contaminated with PCBs, at levels
ranging from 1 to 10 000 nanograms per gram
soil. These numbers can be compared to remote
background areas with 0.9 nanograms
PCBs per gram soil. As is apparent from measurements
in soil and plants, the severely contaminated
soils have served as a source to
nearby areas.
Contamination at radar stations is probably
not unique to Canada. For example, some Alaskan
installations have hazardous waste sites,
measurements near Thule in Greenland show
elevated levels of PCBs, and the Norwegians
have documented elevated PCB levels at dump
sites on Jan Mayen and Svalbard. In Russia, no
studies to look for possible local contamination
by PCBs or other POPs have been reported.
Power stations, oil platforms, mines,
and trains are potential PCB sources
Electrical equipment is also used in power stations,
and old equipment is still a potential
source of PCBs. For example, in Canada, some
temporary wartime power stations and other
installations in the Yukon Territory are known
to have contaminated the soil locally. An inventory
of PCB contamination in the Yukon
Territory has also identified the use of PCBcontaminated
oil to control dust on the streets
of Whitehorse.
77
Persistent Organic
Pollutants
Other historical sources include electric
trains, which may have spread PCBs along
their tracks from leaking transformers, and
hydraulic and drilling fluids from mines and
oil platforms. When a fire destroyed the British
oil platform Piper Alpha in 1988, five tonnes
of PCBs were released into the North Sea.
From Svalbard, there are signs that PCBs from
local sources have spread into nearby fjords.
Arctic smelters and pulp mills
have contributed dioxins
Emissions of dioxins and furans are associated
with industrial activities that occur in the Arctic.
Known local sources include iron-ore pelleting
plants at Malmberget, Kiruna, and Svappavaara
in Arctic Sweden, and the smelter
Rönnskärsverken by the Bothnian Bay just
south of the Arctic Circle. In Kirkenes, Norway,
local dioxin contamination has been documented
in freshwater sediment and in whitefish
in a lake near the Syd-Varanger smelter
works. These studies show that smelters can be
significant local sources and that they can also
be important contributors to background levels
in the Arctic. The large smelters on the
Kola Peninsula, the Vorkuta area in the north
Komi Republic, and the Norilsk area are also
likely sources of dioxins and furans, although
this has not been documented. Other suspected
sources include the secondary iron and steel
industry, an aluminum industry, and a ferroalloy
industry in Arctic Norway, as well as two
smelters in Iceland.
Pulp and paper mills located within the Arctic
Ocean’s drainage area that use elemental
chlorine in the bleaching process can contribute
to the load of dioxins and furans. For
example, studies in the Arkhangelsk area show
local contamination along the Severnaya Dvina
River and its tributaries. The levels are
fairly low, however, and the pulp mills along
the river are probably not major sources to the
Arctic Ocean. In North America, studies along
the Peace-Athabasca River system have shown
that pulp mills have in the past released dioxins
and furans, some of which have accumulated
in the sediments of Great Slave Lake.
Other sources of dioxins and furans in the
Arctic include burning wood for heating and
waste incineration. Forest fires may be an
additional natural source.
Levels in the air,
snow, and rain
Air currents are the most important transport
routes by which organic contaminants reach
the Arctic. Measurements of POPs in air can
thus be used to identify source regions.
Measurements of organic contaminants in precipitation
give important information about
how much of the air contamination is scavenged
and further transported to terrestrial,
freshwater, and marine environments.
Air measurements point to mid-latitude
POP-use as source to the Arctic
Hexachlorocyclohexane is the predominant
organochlorine in air. The figure left shows
concentrations from five different stations. A
summer decrease in some measurements is
probably due to precipitation, which cleans
hexachlorocyclohexane out of the air. Spring
peaks may be related to volatilization from the
snow pack.
Other organochlorines that occur in substantial
amounts in Arctic air include PCBs,
toxaphene, and chlordane-related compounds.
Elevated levels of pesticides, especially lindane
and chlordane, have been correlated with
78
Persistent Organic
Pollutants
250
HCH concentrations in air, pg /m3
200
150
100
50
0
200
gamma-HCH
alpha-HCH
150
100
50
0
200
150
100
50
0
100
50
0
100
50
0
Ny-Ålesund, Svalbard, Norway, Apr.-Dec. 1993
Alert, Ellesmere Island, Canada, Jan.-Dec. 1993
Tagish, Yukon, Canada, Jan.-Dec. 1993
Dunai Island, Lena River Delta, Russia, Mar.-Dec. 1993
Heimaey Island, Iceland, Jan.-Dec. 1995
Ny-Ålesund
Dunai Island
Alert
Heimaey
Tagish
J F M A M J J A S O N D
J F M A M J J A S O N D
J F M A M J J A S O N D
J F M A M J J A S O N D
J F M A M J J A S O N D
Month
Hexachlorocyclohexane
levels in air showing
concentrations of alphaHCH
(height of light
green bar) and gammaHCH
(height of dark
green bar).
long-range transport from use areas farther
south. These results, summarized in the map at
top right, demonstrate that current and past
use of organochlorines in the mid-latitudes of
the northern hemisphere is the most likely
source to the Arctic environment. The compounds
are resistant to environmental degradation
and have high enough volatility to continue
to cycle.
Russian snow and rain have unexpectedly
high levels of PCBs and DDT
Measurements of contaminant levels in snow
provide an indication of how much of the airborne
material stays in the Arctic, since snow
is very effective in scavenging particles from
the atmosphere.
Concentrations of DDT and PCBs in snow
from the Taimyr Peninsula and Laptev Sea,
Russia, in 1995 were about ten times higher
than in the Canadian Arctic, with PCB concentrations
averaging 10 nanograms per liter.
These high levels are especially alarming considering
that only seven PCB components were
measured; total PCB levels can be much higher.
There may be problems with unintentional
contamination during sampling, and there is a
need to confirm the high values.
The tables show some examples of precipitation
measurements.
Levels in terrestrial
environments
The main concern in the terrestrial environment
is that contaminants that end up in
plants can be carried through the food web, as
the plants become food for grazing mammals
and birds. Plants, especially perennial mosses
and lichens, can also give a good indication of
how much of the airborne contaminants are
deposited to the surface within the Arctic; see
the figure to the right.
Except for locally polluted sites, levels in
plants are generally low compared to industrialized
areas farther south. PCBs, DDT, and
hexachlorocyclohexane dominate. Although
toxaphene was measured in only one place,
Ellesmere Island, it was the most abundant of
all POPs. Even across small geographic areas,
there is a gradient from higher concentrations
of organochlorines in the south to lower concentrations
in the north. This gradient appears,
for example, in data from Finland and from
Ellesmere Island.
Measurements in soil have mostly been carried
out at sites known to be contaminated, such
as the Canadian DEW Line sites. These local
levels are high enough that the soil can serve as
a source of PCBs to the surrounding ecosystem.
Elevated PCBs
and HCH from
Russia/Siberia
Elevated PCBs
and HCH from
Russia/Siberia
‘Clean’ air;
low toxaphene
over NW Pacific
‘Clean’ air; low chlordane
and PCBs across
the Arctic Ocean
Elevated
toxaphene
from US/Canada
west coast
Elevated chlordane
originating from
US/Canada
east coast
Elevated PCBs
and HCH
originating from
Europe and
western Russia
Tagish
Alert
Ny-Ålesund
50
40
30
20
10
0
5
6
7
4
3
2
1
0
Mosses Lichens
PCBs, ng/g dry weight
POP concentrations in Russian samples, ng/liter.
–––––––––––––––––––––––––––––––––––––––––––––––––
HCH DDT PCB
–––––––––––––––––––––––––––––––––––––––––––––––––
Snow, May 1995
Taimyr Peninsula 5.61 2.06 5.3
Precipitation, August 1994
Taimyr Peninsula 0.88 3.28 11.98
Laptev Sea < 0 .18< 1.18 1.1
Barents Sea 0.67 0.34 4.3
–––––––––––––––––––––––––––––––––––––––––––––––––
Deposition of POPs to snow in Canada, mg/m2/season.
–––––––––––––––––––––––––––––––––––––––––––––––––
HCH DDT PCB
–––––––––––––––––––––––––––––––––––––––––––––––––
Alert 1992/93 0.88 0.05 0.19
Alert 1993/94 0.50 0.05 0.37
Eureka 1991/92 0.78 0.01 0.26
Mould Bay 1993/94 0.25 0.03 0.23
Cape Dorset 1993/94 0.22 0.06 0.51
Dawson City 1993/94 0.19 0.04 0.41
Whitehorse 1993/94 0.12 0.02 0.20
Tagish 1992/93 0.28 0.01 0.24
Tagish 1993/94 0.20 0.04 0.35
–––––––––––––––––––––––––––––––––––––––––––––––––
Pathways and source
regions for POP-contaminated
air.
Average concentration
of PCBs in moss and
lichen.
79
Caribou and reindeer
have low levels of POPs
Caribou and reindeer feed on ground vegetation
and can potentially accumulate contaminants
from the plants. The major contaminants
ending up in the animals are hexachlorobenzene
and hexachlorocyclohexane,
reflecting the predominance of these contaminants
in atmospheric deposition to their grazing
areas. The levels seem to be fairly uniform
across the Arctic; see the figure below. However,
Russian results from two consecutive
years differ considerably. Excluding Russia,
mean hexachlorobenzene concentrations in the
dataset for Canada and Svalbard range from
0.3 to 3.7 nanograms per gram liver (wet
weight) and hexachlorocyclohexane concentrations
range from 0.9 to 8 nanograms per
gram liver (wet weight) in caribou, which are
extremely low levels. For Russia, mean hexachlorobenzene
levels range from 0.09 to 7.6
nanograms per gram liver and hexachlorocyclohexane
levels from 0.2 to 7.5 nanograms
per gram liver, depending on the year.
For DDT and PCBs, the levels in Russian
reindeer liver (for both years) are higher than
in other areas, which is also true for other
ground-feeding animals such as lemming,
ptarmigan, and brant.
Levels in North American caribou show a
more varied geographic picture for PCBs and
DDT than for other compounds. This may
reflect a greater influence of contaminants
from regional sources in North America relative
to global distribution.
There is no information about biological
effects of organic contaminants in reindeer/
caribou, but in general, the levels are several
orders of magnitude lower than those expected
to cause effects.
The levels in caribou have also been used to
examine the biomagnification of contaminants
in the terrestrial food chain from lichen to
caribou to wolf. The diagram at the bottom of
this page shows that PCBs accumulate for each
step in the chain and thus that biomagnification
occurs in the terrestrial environment. A
closer look at the different components of
PCBs reveals that wolves are able to break
down some substances, but that the most persistent
remain.
Waterfowl carry contaminants
from overwintering areas
Waterfowl and terrestrial game birds and their
eggs are food sources for people as well as for
birds of prey, such as the peregrine falcon. A
study of Canadian waterfowl shows that some
of the birds probably carry substantial burdens
of contaminants from their overwintering
areas farther south. For example, birds from
eastern North America have much higher levels
than birds from farther west. The traditional
overwintering areas for eastern birds are
the Great Lakes, the Gulf of Mexico, and the
eastern American seaboard, which are all relatively
polluted environments. Mirex, which is
a typical contaminant of the lower Great
Lakes, only shows up in the eastern birds.
In general, the levels in waterfowl are low,
in the nanogram per gram range (whole body),
but with some exceptions. Birds feeding on fish
and mollusks have higher levels than those eating
plants, which reflects their higher position
in the food web. Also, oldsquaw, pintail, and
some individuals of semipalmated plover have
PCB levels that exceed the thresholds for reproductive
system effects in other birds.
The Canadian peregrine falcon
still suffers from eggshell thinning
The peregrine falcon is a predatory bird that
has suffered badly from high levels of pesticides
in the environment. This includes the populations
of the subspecies that breed in the North
American Arctic, Falco peregrinus tundrius,
which feed on waterfowl and small rodents.
Studies in the Canadian Arctic show average
PCB levels of 8.3 micrograms per gram and
DDE levels of 4.5 micrograms per gram egg.
It is difficult to know whether Arctic populations
are recovering as fully as those in
80
Persistent Organic
Pollutants
HCH in caribou/
reindeer liver,
ng/g wet weight
10
1
~ 0
10
20
30
40
50
60
0
PCBs,
ng/g lipid weight
Iñuvik Cambridge Bay Bathurst Island
Wolf
Caribou
Lichen
Iñuvik
Cambridge Bay
Bathurst Island
Hexachlorocyclohexane
levels in caribou/reindeer
liver. Russian data are
based on one individual
per site.
Biomagnification of
PCBs from three sites in
Canada.
northern temperate areas. The number of birds
is naturally low, and large fluctuations in population
size make recovery hard to monitor.
However, in the early 1990s, contaminant levels
in the birds were still high enough to reduce
eggshell thickness. In 1991, 28 percent of the
clutches showed thinning equal to or greater
than the threshold level that has been associated
with failure to reproduce.
Since the early 1980s, in spite of bans on
DDT in all the circumpolar countries, eggshell
quality in this population of tundra peregrines
has not improved. Levels of DDE, dieldrin,
and heptachlor epoxide were lower in the early
1990s than in the early 1980s, but female
peregrines had higher levels of PCBs, four
times the maximum value reported in the
1980s. Moreover, chlordane seems to be increasing
again in the eggs, which is probably a
result of an increased use of this pesticide.
The source of the contaminants in peregrine
falcons is the migratory waterfowl on which the
peregrines prey. A study at Rankin Inlet showed
that levels of PCBs in oldsquaw (long-tailed
duck) and pintail were high enough to lead to
reproductive effects in peregrine falcons. The
threshold levels for DDE were exceeded in oldsquaw,
water pipit, and semipalmated plover.
These birds are especially important in the diet
of female peregrines. Several other contaminants
were also detected in the prey, but not at
levels high enough to affect peregrine reproduction.
Predatory birds that feed mostly on
animals resident year-round in the Arctic have
much lower levels of contaminants.
The Committee on the Status of Endangered
Wildlife in Canada previously considered the
tundra peregrine falcon threatened. The status
has been changed to vulnerable because the
chemical threat did not appear as great as
before. These recent results suggest that the
threat is still present.
Icelandic gyrfalcon
accumulate POPs with age
A study of gyrfalcon in Iceland shows that
these birds of prey accumulate organic contaminants
over their lifetime. Among birds that
were found dead in Iceland, the levels in recently
hatched birds were about 100 nanograms
DDT and DDE combined per gram muscle. In
ten-month-old birds, the concentration was a
hundred times greater; in 20-month-old birds,
it was a thousand times greater than in the
hatchlings. Since most of the birds in the study
were young, the average levels in the population
could have been even higher than the
levels reported here. The gyrfalcons are yearround
residents in Iceland but probably feed
on migratory birds that are contaminated.
The study also showed that the concentrations
of PCBs and DDT were higher in leaner
birds than in birds with more fat. Most organic
contaminants are normally stored in fat, and
using fat reserves may have released enough
DDT and PCBs into the birds’ vital organs to
contribute to their deaths.
Fennoscandian birds of prey
are recovering
In Fennoscandia, white-tailed sea eagle, osprey,
merlin, peregrine falcon, and eagle owl have
all suffered from high concentrations of organic
contaminants. From the 1950s to 1970s, eggshell
thinning and lowered reproductive capacity
led to population declines. For most of the
birds, the trend has now reversed and their populations
are starting to recover. This recovery
coincides with the decline in environmental
levels of DDT and PCBs.
While the situation has improved, the problems
have not disappeared. Merlin from Alta
in Norway still have about 10 percent eggshell
thinning on average, and in some cases their
DDT levels remain high enough to cause concern
about reproductive success. Peregrine falcons
also have PCB levels above the lowest that
cause reproductive effects in other birds; see
diagram on page 87. There is some concern
about current contaminant levels in the food of
Norwegian white-tailed sea eagles: PCB (diagram,
page 88) and DDT levels in a range of
fish species from Arctic sites exceed several of
the guidelines for protecting fish-eating wildlife.
Studies of a population of peregrine falcons
on the Kola Peninsula also conclude that contaminant
levels are high. Dioxin was found in
concentrations that are associated with embryonic
mortality in other bird species.
American mink and marten
have low contaminant loads
American mink and marten feed on small
mammals and fish throughout the forested
region of North America and can potentially
accumulate organic contaminants from both
terrestrial and freshwater environments. Mink
are known to accumulate PCBs, to which they
are extremely sensitive. Even levels as low as
72 nanograms per gram food can lead to a
failure to reproduce.
The levels of PCBs in American mink and
marten in the Arctic are low in most places
that have been investigated. The exception is
mink from Grand Baleine, Quebec, in eastern
Canada, which have PCB levels that are just
below the no-effect level for litter size. Also,
fish from several lakes have PCB levels that
may be high enough to cause reproductive
effects if they are eaten by mink.
Scandinavian mink and otter
are bouncing back
The American mink was introduced to Scandinavia
in the 1940s. At first, the population increased
rapidly but then leveled off in the 1960s
81
Persistent Organic
Pollutants
and declined in the early 1970s. The chief
cause of the decline was most likely high exposure
to organic contaminants, particularly
PCBs. After a 50-percent reduction in environmental
levels of PCBs from 1975 to 1978, the
mink population began increasing again.
Otters in the Swedish Arctic are now experiencing
a similar recovery. The population
declined rapidly from the 1950s to the 1970s,
and by 1980 only a few isolated groups survived.
From the end of the 1980s and into the
1990s, the northern population has suddenly
been increasing again.
By analyzing PCB levels in otter muscle, it
has been possible to determine a threshold
concentration of contaminants above which an
otter population will suffer. Muscle tissue levels
above 7.5 to 25 micrograms per gram lipid
lead to population declines, whereas concentrations
below 7.5 micrograms per gram lipid
allow a population to recover. Norwegian
otter populations that live along the Arctic
coast fall in the low range and have indeed
remained constant or even increased slightly.
The levels of PCBs may, however, be high
enough to affect neurobehavioral development.
Levels of dioxins and dioxin-like PCBs
in Swedish otter are above those associated
with immunosuppression in seals.
Red fox and wolf
The food habits of fox and wolf differ greatly
depending on geographic area and time of year.
Red fox typically prey on smaller mammals,
but also eat insects, reptiles, fish, and berries.
Wolf packs often follow and hunt caribou. Red
fox and wolf samples from Canada contained
measurable levels of POPs, of which PCBs
were most prominent. The levels were highest
in fox, probably reflecting generally higher
contamination levels in the northern Quebec
environment in which they were studied.
Levels in freshwater
environments
The freshwater environment reflects the combined
input of contaminants from the air and
from runoff. Most of this contamination is the
result of long-range transport from temperate
industrialized regions. Local contamination is
a problem in some lakes in the Arctic.
Some Russian rivers and lakes
seem to be very contaminated with POPs
Hexachlorocyclohexane is the main POP
detected in river water. The diagram below
shows levels of hexachlorocyclohexane in
rivers from across the Arctic. Most noteworthy
are the exceptionally high levels in some Russian
rivers, especially the Ob. A high ratio of
gamma-hexachlorocyclohexane to alpha-hexachlorocyclohexane
indicates input of the pesticide
lindane.
DDT, too, was detected in river water, with
concentrations ranging from 0.03 nanograms
per liter in rivers draining into Hudson Bay to
5 nanograms per liter in the Ob River.
Russian data also include analyses of suspended
particles. Some of the contaminants
are present on particles at levels 10 to 100
times higher than have been recorded from
Canadian or Norwegian rivers. For example,
PCB concentrations up to 26.6 micrograms per
gram dry weight and DDT concentrations up
to 2.75 micrograms per gram dry weight have
been recorded. Further investigations are
needed before drawing any final conclusions,
but if verified, these data show that some
Russian rivers draining into the Arctic Ocean
are more contaminated than surface waters in
urban areas of North America and western
Europe. These rivers could constitute a significant
source to the Arctic Ocean.
Studies of lake water are only available
from a few lakes in Canada and from two
lakes in Russia. Hexachlorocyclohexane, hexachlorobenzene,
and toxaphene have been
detected, as have several less-persistent
organochlorines. This suggests that lake water
can be an important reservoir for water-soluble
organic contaminants. PCB levels in lake
water in Canada exceed USEPA quality guidelines
for protection of aquatic wildlife (0.017
nanograms per liter).
The data from Russian lakes, from the Taimyr
Peninsula, mirror the high levels of hexa-
82
Persistent Organic
Pollutants
Hexachlorocyclohexane
levels in river water.
0 5 10 15 20HCH, ng / liter
Yukon River
Mackenzie, Arctic Red
Mackenzie East
Mackenzie West
Andrews
Coppermine
Burnside
Ellice
Back
Hayes
Thelon
Dubawnt
Kazan
Quoich
Lorillard
Orkla
Vefsna
Alta
Olenek
Lena
Yana
Kolyma
Pechora
Kola, north
Kola, south/east
Northern Dvina
Mezen
Ob
Taz
Yenisey
Pyasina
Anabar
Central NWT, Canada
Mackenzie River delta, Canada
Yukon, Canada
Hudson Bay area, Canada
Northern Norway
Eastern Russia
Ob and Yenisey region, Russia
Kola and White Sea region, Russia
Pechora region, Russia
chlorocyclohexane, DDT, and PCBs that were
found in river water. PCB levels are high
enough to exceed Canadian environmental
quality guidelines (1 nanogram per liter).
Again, because of possible quality assurance
problems, these measurements need to be verified
before firm conclusions are drawn.
Lake sediments have low levels of POPs
The figure to the right shows the levels of DDT
and PCBs in lake sediments from remote areas
of the Arctic. Persistent organochlorines appear
in most of the sediments, with concentrations
ranging from 0.01 to 40 nanograms per gram
dry sediment. These concentrations are similar
to or lower than those in sediments from midlatitude
lakes in North America and much lower
than those in industrialized areas. One exception
is Wonder Lake in central Alaska (240 nanograms
PCBs per gram dry sediment), which
may indicate local contamination. The levels in
Wonder Lake are above the median effect range
in environmental guidelines for aquatic life.
Five lakes in Canada, one in Norway (on Bear
Island), and one in Russia (on the Taimyr Peninsula)
exceeded the minimal effect range.
The south–north comparison of available
data from Canada, Alaska, and Finland shows
that PCB levels in lake sediments decrease sixfold
from 46°N to 81°N.
Core samples of lake sediments give a picture
of how the deposition of contaminants
has changed over time. PCBs first appear in the
1940s and their input peaks in the 1970s and
early 1980s, which corresponds to the maximum
use of PCBs in industrialized areas. In
the Canadian High Arctic, the onset as well as
the peak come somewhat later. This supports
the idea that time trends in deposition of persistent,
semi-volatile organic compounds in the
polar region will be delayed and prolonged
compared with areas closer to the sources.
Dioxins and furans have also been analyzed
in some lake sediments. The levels in all sediments
exceeded the Canadian environmental
quality guidelines for protecting aquatic life
(0.09 picograms per gram dry weight). In
Great Slave Lake, Canada, the chemical signatures
point to two different sources: combustion
and the effluent from bleaching in pulp
mills in the Peace-Athabasca-Slave River basin.
The peak in deposition in the 1950s coincides
with increased industrial activity in the region
to the south of the lake, with the introduction
of two chlorine-bleached kraft pulp mills
within the drainage basin, and with the use of
pesticides contaminated with dioxins and
furans. The mills have since switched to elemental-chlorine-free
bleaching.
Sediments from a few lakes in northern
Finland, Norway, and Sweden also contain
dioxins and furans. Air transport from combustion
sources seems to be the only logical
source. The levels in these lakes are about ten
times higher than in the lakes studied in
Canada, and similar to background levels in
some other areas of Europe.
Canadian data point to toxaphene
as a major contaminant in freshwater fish
The general picture for animals in freshwater
systems is that levels of organic contaminants
are higher than in the terrestrial environment,
but in most cases below levels that would pose
problems for fish. In a few cases, however, the
contaminant levels are high enough to affect
the quality of the fish as food.
Based on measurements mostly from
Canada, the major contaminant in fish is toxaphene.
There are no known current sources of
toxaphene in the Arctic, and the contamination
probably derives from long-range transport.
Levels are highest in fish that feed on
other fish, such as lake trout and burbot. Burbot
liver is of special concern because its high
fat content seems to increase its ability to accumulate
organic compounds. The toxaphene
levels in burbot measured in Canadian lakes
range from 40 to 2300 nanograms per gram
liver. These levels are close to those known to
affect bone development and reproduction in
other fish.
PCBs and DDT levels
(dry weight) in surface
sediments from remote
lakes.
25 30 35 40 45 50 55
PCBs and DDT in lake sediments
PCBs, ng/g
< 2
2-7
7-15
15-25
25-40
> 40
DDT, ng/g
< 0.25
0.25-1
1-2
2-4
4-5.25
83
Freshwater fish also have PCBs, DDT, some
chlordane-related compounds, hexachlorocyclohexane,
and hexachlorobenzene in their
bodies. Excluding a few hot spots, the levels of
PCBs in lake trout, a predatory fish, range
from 9 to 450 nanograms per gram. The map
above shows the contaminant levels in landlocked
and migratory Arctic char.
Lake Laberge has high levels of all POPs
Some hot spots of contamination cannot be
explained by local sources. One such example
is Lake Laberge in Canada, downstream from
the community of Whitehorse. The lake is used
for commercial, sports, and native subsistence
fishing. Analyses of lake trout, burbot, and
lake whitefish revealed that the levels of PCBs,
DDT, and toxaphene were 30 times higher
than in other lakes in the Northwest Territories,
and comparable to contaminant levels
in the severely polluted Great Lakes.
There have been numerous suggestions
about the sources of these contaminants. Current
scientific opinion is that long-range air
transport is the major pathway, which in combination
with changes in food-web structure
has led to significant biomagnification. For example,
lake trout in Lake Laberge eat only fish
and have much more fat in their bodies than
lake trout in other lakes in the region. Changes
in the food web have been attributed to overfishing
and to increased productivity due to
nutrients from the Whitehorse sewage lagoon.
Levels in
marine environments
The Arctic marine environment collects contaminants
from the air, but also from ocean currents,
rivers discharging into the Arctic Ocean,
and sea ice that transports POP-laden particles.
Seawater measurements reflect
pathways of contaminant transport
The table below presents some examples of
contaminant levels in seawater. Hexachlorocyclohexane
dominates the picture, except for
Russian waters where PCB levels are high, up
to 15 nanograms per liter in the Kara Sea.
These high levels seem to mirror the high input
of PCBs from Russian rivers.
Hexachlorocyclohexane levels are highest in
the Canadian Archipelago. The permanent ice
POP levels in landlocked
and migratory Arctic
char.
Organochlorine concentrations in seawater, pg/liter.
––––––––––––––––––––––––––––––––––––––––––––––––––
alpha-HCH DDT PCB
––––––––––––––––––––––––––––––––––––––––––––––––––
Norwegian Sea, 1985 2750 <50 <500
Barents Sea, 1992 477 3 38
Laptev Sea, 1994 260 760 2540
Kara Sea, 1994/95 120-560 50-1250 510-3940
Pechora Sea, 1992 330 270 550
Canadian Archipelago, 1992 4180 1.0 –
Bering Sea, 1990 1500 1.0 12
Bering Sea, 1993 1990 – –
Chukchi Sea, 1990 1400 0.3 8.4
Chukchi Sea, 1993 2060 – –
––––––––––––––––––––––––––––––––––––––––––––––––––
84
Persistent Organic
Pollutants
&(
&(
Dwarfs Normal
Kola Peninsula
Lake 222
Abiskojaure
Pahtajärvi
Lake Hazen
Buchanan Lake
Thule
Nuuk
Kongressvannet
and Linnevann
Diesetvannet
and Rickardvannet
Ammasalik
Isortoq
Kangiqsualujjuaq
Inukjuaq
Peter Lake
Talurjuac Somerset Island Char Lake
Kangiqsujuaq
Salluit
Amituk Lake
MittitimatalikSanikiluaq
2
1
0
2
1
0
µg/g lipid weight
CHL
DDT DDT
Toxaphene
PCBs
CHL
Toxaphene
PCBs
Landlocked
Arctic char
Migratory
Arctic char
Lake Blasjon
cover in the Canadian Basin does not allow dissolved
hexachlorocyclohexane to outgas very
easily, and the high concentrations in surface
water probably reflect higher hexachlorocyclohexane
concentrations in the atmosphere a
decade or so ago. Toxaphene is similarly
trapped under the polar ice cap as a ‘ghost of
the past’. These contaminants will slowly drain
through the Canadian Archipelago over several
decades. A closer look at seasonal changes
in concentrations also reveals that some
toxaphene probably follows particles settling
on the sea bottom during the summer peak of
productivity.
Levels in seawater can also be used to shed
light on the mechanisms that transport contaminants
to the Arctic. Detailed measurements
in the Bering and Chukchi Seas (see the figure
above) show that hexachlorocyclohexane levels
in the water increase along a south–north
gradient. This has been suggested as evidence
for a cold-condensation theory; that semivolatile
contaminants condense out of the atmosphere
as temperatures drop. Less volatile
contaminants, such as PCBs, DDT, and chlordane,
were present at lower levels in the
Bering and Chukchi Seas than in more temperate
latitudes.
Marine sediments
are comparatively clean
Concentrations of organic contaminants in Arctic
marine sediments are, in general, extremely
low compared with freshwater sediments, and
ten to a hundred times lower than in the Baltic
Sea. The most apparent geographic trends are
that concentrations of PCBs, hexachlorocyclohexane,
and hexachlorobenzene are higher closer
to the shore along the Norwegian coast than
in the open sea. They are also higher in gulfs and
river mouths along the Russian coast, and
around Svalbard; see figure below. Industrial and
municipal effluent as well as runoff and river
water are probable explanations in some areas.
In some places, dumping influences local
sediment levels. Two examples of PCB-pollu-
85
Persistent Organic
Pollutants
ᮤ
Alpha-hexachlorocyclohexane
concentration in
seawater increases moving
from south to north,
illustrating the cold-condensation
effect.
PCB concentrations in
marine surface sedi-
ments.
Chukchi Sea
Beaufort
Sea
Bering
Sea
North Pacific Ocean
Okotsk
Sea
Java Sea
East China Sea
5
4
3
2
1
0
alpha-HCH in seawater,
ng/liter
Contaminant budget for the Arctic Ocean
Information about levels of contaminants in seawater and river water along with
equations describing exchange with the atmosphere have been used to calculate
budgets for hexachlorocyclohexane, toxaphene, and PCBs. The results for hexachlorocyclohexane
are presented here. The picture that emerges is that the Arctic
Ocean is in a steady state for gamma-hexachlorocyclohexane and that it is exporting
alpha-hexachlorocyclohexane. Therefore, we can expect a decline in the large
pool of alpha-hexachlorocyclohexane in the Canadian Basin.
For toxaphene, lack of data prevents a detailed mass balance calculation, but
the available information suggests that inputs and outputs of toxaphene are
roughly equal. The atmosphere accounts for slightly more than 40 percent of the
input. Volatilization is an important loss process, though most toxaphene is removed
by ocean currents via the Canadian Archipelago and Greenland.
The mass balance for PCBs is preliminary and based on some results from
Russian rivers, that have to be verified. The current picture indicates that inputs
exceed outputs by 50 percent. 24 percent of the overall input is via rivers. Some
portion of PCBs is removed by settling particles, but most of the export is via
ocean currents.
Ice
273
97
73
64
4
47
21
79
47
48
0.2
Atmospheric
input
Volatilization
Arctic Ocean
total HCH budget,
tonnes/year
Russian rivers
North American rivers
PCBs, ng/g dry weight
<0.5
0.5-1
1-2
2-5
5-9
>9
ted military sites are Cambridge Bay harbor
off Victoria Island in Canada and Thule in
North Greenland.
Dioxins and furans also show up in marine
sediment, but at low levels. Concentrations in
the Barents Sea, for example, are ten to twenty
times lower than those in the North Sea. The
chemical signature suggests that combustion is
the major source.
Marine food webs are not well studied
One of the major concerns in the marine environment
is that POPs are incorporated in the
fat of small invertebrates low in the food web
and subsequently accumulated and biomagnified
by larger animals. Levels of persistent
organic pollutants in marine food webs are
poorly studied. Available measurements show
that contaminant levels in fish are generally
lower in the Arctic than in temperate seas.
The highest levels occur in predatory fish,
high on the food chain. Greenland halibut
from Canada have levels of toxaphene that are
close to those known to affect bone development
and reproduction.
Military radar sites
may have contaminated marine fish
PCB and DDT levels are high close to several
military sites and accompanying communities.
At Cambridge Bay off Victoria Island in Canada,
a DEW Line radar station has contaminated
the local marine environment. At this
site, DDT levels in benthic predatory fish such
as fourhorn sculpins averaged 25 nanograms
per gram muscle and PCB levels averaged 50
nanograms per gram muscle. However, the
nearby bays were not contaminant-free, and
an analysis of the pattern among the POPs
showed that rivers can also be a significant
source of contamination along the coast.
Some seabirds
have very high PCB and DDT levels
Seabirds breeding in the High Arctic are contaminated
with the same suite of compounds as
those breeding in temperate regions. The levels
vary depending on feeding habits; see the diagram
above. The common eider and king eider,
which feed on mussels, have the lowest levels,
whereas fish-eating cormorants (shag) have relatively
high levels. Other birds with high levels
are the glaucous gull, black-legged kittiwake,
and puffin. A study of seabird eggs showed
that glaucous gulls from Prince Leopold Island
in the Canadian High Arctic had organochlorine
levels four to ten times higher than other
birds in the area, reflecting their position as a
top predator in the marine food web.
In migratory seabirds, the load of contaminants
mirrors migratory habits. Eiders in LowArctic
Canada that overwinter off Newfoundland
and in the Gulf of St. Lawrence, in waters
that are known to be contaminated, have a contaminant
load that is considerably higher than
that of populations that overwinter in northern,
cleaner waters. There is also a general
geographic pattern with cleaner birds in the
west of Canada than in the eastern Low Arctic.
A study of birds from Svalbard, the northern
Norwegian coast, and the Kola Peninsula
found no major differences between the three
areas. The birds may share the same overwintering
areas, and contaminants are probably
well mixed throughout the Barents Sea.
Do Arctic marine birds suffer from their
load of toxic compounds, as has been clearly
shown in birds from polluted environments?
In general, contaminant levels in the Arctic are
lower than in, for example, the Great Lakes
region, but a study of glaucous gulls from
Svalbard brings some disturbing observations.
Birds that were found dead of unknown causes
had high concentrations of PCBs in their fat.
The birds were probably starved and stressed
before they died, and it could be that the elevated
levels of PCBs in their remaining fat
were high enough to affect vital functions in
the birds. The levels of contaminants in eggs
from species on which the glaucous gull feeds
are higher in Svalbard than in, for example,
the Canadian High Arctic.
A comparison to known low-effect levels in
other bird species also causes concern. The
diagram at the top of the opposite page shows
that PCB levels in seabirds from the Canadian
and Norwegian Arctic approach or exceed lev-
86
PCB concentrations in
seabird eggs.
Com
m
on
eider
G
laucous
gull
Black
guillem
ot
King
eider
Black-legged
kittiwake
Com
m
on
eider
G
laucous
gull
Com
m
on
eider
Black-legged
kittiwake
Shag
Northern
fulm
ar
G
laucous
gull
Com
m
on
guillem
ot
King
eider
Black-legged
kittiwake
Shag
Puffin
Herring
gull
King
eider
Black-legged
kittiwake
10
20
30
5
Canadian
Low Arctic
Canadian
High Arctic Troms, Norway Finnmark, NorwaySvalbard
PCBs in seabird eggs,
µg/g lipid weight
Svalbard
Finnmark
Troms
Canadian
Low Arctic
Canadian
High Arctic
els that are known to affect reproduction in
other bird species. PCB levels in cormorant
(shag) and fulmar are at or above the loweffect
level for embryo deformities and the
low- or no-effect level for hatching success.
Puffin, thick-billed murre, common guillemot,
black guillemot, and kittiwake have levels that
exceed the upper no-effect level for hatching
success. PCB levels in glaucous and herring
gulls are even higher and approach or exceed
the low-effect level for hatching success.
Toothed whales have high levels of POPs
The levels of contaminants in different species
of whale also reflect their feeding habits.
Beluga, narwhal, and harbor porpoise eat fish
and have higher levels of contaminants than
minke whale, which mostly eat invertebrates.
Harbor porpoise from Northern Norway
had the highest levels of PCBs and DDT of any
of the whales in Arctic waters and were in the
same range as animals from southern Norway;
see the map below. These PCB levels exceed
the threshold for immune toxicity. In North
American waters, PCB levels in beluga range
from 2.6 to 6.0 micrograms per gram blubber.
The levels of contaminants in whales and
other Arctic marine mammals are higher in
males than in females and also depend on the
age of the animal. Adult female whales usually
have lower levels than adult males. In males,
unlike females, the levels increase with age.
Studies of cow–calf pairs show that whales get
a large portion of their load of organochlorines
very early in life, from their mother’s
milk. Females have accumulated large burdens
by the time they begin to reproduce, and pass
this on in marine mammal milk which is very
rich in fat. In the newborn calf, this initial dose
is further concentrated as the young animal
uses the fat for energy. Only when it starts
feeding on its own will the contaminants from
the milk be diluted in its body. For the female,
nursing the young rids her body of some of its
contaminant load, which is why reproducing
females have much lower concentrations of
organochlorines than males of the same age.
How do the contaminants affect the whales?
One study shows that when whales are starved,
PCB levels may affect their livers. The whales in
this study had entered a freshwater lake system
when the water was free of ice and were trapped
when winter set in. Their breathing holes became
smaller and smaller. By mid-winter, native
hunters decided to harvest the animals. At this
time they weighed about 200 kilograms less that
healthy whales of the same length. This starvation
probably forced the whales to use their
blubber fat for energy, which in turn increased
the concentration of PCBs in the remaining fat.
A correlation was seen between PCB levels and
the amounts of liver detoxifying enzymes. One
conclusion is that currently-observed body burdens
of contaminants can be associated with
subtle effects when a lack of food forces whales
to burn fat reserves for energy.
For assessing effects other than on the liver,
we must rely on comparisons with known effects
levels in other species and other tissues;
see the diagram on the next page. The major
concern seems to be PCBs, the levels of which
range in blubber from 1.9 to 6.3 micrograms
per gram lipid. This is higher than the no-effect
and low-effect levels associated with subtle
neurobehavioral effects (assuming that levels
in blubber reflect levels in blood serum), but
below the no-effect level for reproduction and
kit survival in mink. PCB levels in fish from
some sites are also high enough to cause concern
about effects from the whales’ diet.
21
Eiders
Black
guillem
otShagM
urre
Com
m
on
guillem
otFulm
arPuffin
Kittiwake
G
laucous
gull
Herring
gull
M
erlin
Norwegian
white-tailed
sea
eagle
Kola
white-tailed
sea
eagle
Canadian
peregrine
(anatum
)
Canadian
peregrine
(tundrius)
Fennoscandian
peregrine
Kola
peregrine
Reproduction*, night heron
Reproduction**, common tern
Hatching success**, common tern
Deformities**, cormorant
Deformities**
Hatching success*
Hatching success**
Egg mortality, deformities**,
herring gull
Egg mortality**, bald eagle
Egg mortality**, cormorant
Hatching success*, Forster’s tern
white
leghorn
chicken}
10
11
12
13
14
15
16
9
8
7
6
5
4
3
2
1
0
PCBs, µg/g wet weight in eggs
Seabirds Birds of prey
10
5
0
Harbor porpoise
Minke whale
PCBs, µg/kg blubber
PCB levels in eggs from
seabirds and terrestrial
birds of prey compared
to different thresholds
for biological effects.
* no-observed-effect
level (NOEL)
** lowest-observedeffect
level (LOEL) or
lowest-observedadverse-effect
level
(LOAEL).
+ refers to average
values.
87
PCB concentrations in
blubber from harbor
porpoise and minke
whale from Norway.
Parts of the diet of some seals are also contaminated
enough to cause concern. If seals are
as sensitive to PCBs as mink, on which most
diet studies have been done, several fish species
exceed no-effect concentrations for dietary
intake; see left panel below.
POP levels in walrus
reflect their feeding habits
Walrus feed mostly on bottom-dwelling animals
that have low levels of organic contaminants.
However, high levels of PCBs in some
animals suggest that there are important exceptions.
Nineteen of 53 walruses from across
the Canadian Arctic had more than 1 microgram
PCBs per gram blubber. These results
suggest that some walrus probably have ringed
seal as an important part of their diet. The
high levels were recorded in walrus from east
Hudson Bay, Foxe Basin, and east Baffin
Island. Walrus from Svalbard have levels of
PCBs as high as walrus from east Hudson Bay.
No one has studied the biological effects of
POPs on walrus. However, a comparison of
known-effects levels from otter and mink show
that walrus from east Hudson Bay and Svalbard
exceed the no-effect levels for reproduction
and kit survival. PCB and dioxin levels in
seal-eating walrus are similar to the lowest levels
that have been associated with immune
suppression in seals.
Polar bears are at risk
for immune and reproductive effects
As a top predator in the marine food web, the
polar bear could be the species most exposed
to contamination of the Arctic environment.
Hudson
Strait
NE
GreenlandSkjanesJarfjordW
Russia
Nom
eBarrowHolm
anResoluteEureka
Arviat
N
Baffin
Island
SanikiluaqInukjuaq
Pangnirtung
Thule
Disko
NanortalikScoresbySvalbardJarfjord
Yenisey
Gulf
Harp seal Ringed seal
PCBs and DDT in blubber, µg/g wet weight
4
3
2
1
0
DDT
PCB
Seals in the Barents Sea are more
contaminated than in other Arctic regions
The most important contaminants in seals are
PCBs, chlordane, and DDT. The figure above
shows the levels of PCBs and DDT in harp and
ringed seals from Arctic waters. The mean
PCB levels range from 0.24 to 5.7 micrograms
per gram blubber. These are higher than in the
fish they eat, which shows the role of biomagnification
in the Arctic food web, but are still
much lower than in polluted areas such as the
Baltic Sea. PCB and DDT levels in seals seem
to increase from west to east, with the highest
levels seen in seals from Svalbard, northern
Norway, and Russia. The geographic trend for
hexachloroxyclohexane is the opposite, with
the highest levels in Canadian ringed seal.
The loads of PCBs in seals are considerably
lower than those associated with poor reproductive
success in seals from polluted areas,
but exceed the no-effect and low-effect levels
for subtle neurobehavioral effects in laboratory
animals; see below right.
240 000
Peregrine falcon,
highest no-effect
concentration in
food
EC50 kit survival, liver; mink
EC50 litter size, liver; mink
Poor reproduction; ringed seal
Poor reproduction; harbor seal
Immune effects**; rhesus monkey
Kit survival*, muscle; mink
Kit survival*, muscle; otter
Visual memory*, human offspring
cord blood serum
Short-term memory**, human offspring
cord blood serum
US EPA guideline
freshwater guideline
Canadian
marine guideline
IJC guideline
Mink, highest
no-adverse effect
concentration in food
100 000
10 000
1000
100
10
1
10 000
1000
100
10
1
0.1
PCBs in tissue,
ng/g lipid weight
PCBs in prey species,
ng/g wet weight
Lake
whitefish
Burbot(liver)
Lake
troutPike
ArcticcharArcticchar
Broad
whitefishSculpin
Greenland
halibut
Arcticcod
(liver)
Atlanticcod
(liver)
Long
rough
dab
(liver)
Dab
(liver)
Redfish
(liver)
Navaga
(liver)
Div.Greenland
fish
(liver)
Seabird
eggs
Ringed
seal(blubber)
CaribouW
olf
M
ustelidsRinged
seal
Harp
seal
M
inke
whale
NarwhalBelugaW
alrus
Harborporpoise
Polarbear(circum
polar)
Polarbear(Svalbard)
Arcticfox(Svalbard)
Freshwater Marine Terrestrial Marine
}
}
ᮢ
Left: PCB levels in food
items compared to thresholds
for biological effects
and to environmental quality
guidelines to protect
fish-eating aquatic wildlife.
Right: PCB levels in mammals
compared to different
threshold for biological
effects.
* lowest-observedadverse-effect
level
** no-observed-effect level
or no-observed-adverse
effect level
EC50 = concentration at
which half of the animals
in the study were affected.
Geographical trends for
DDT and PCBs in harp
and ringed seals (range
averages). The locations
are arranged from west
to east.
There have been several studies of POP levels
and possible biological effects in polar bear,
especially to examine whether POPs damage
the ability of bears to conceive and to rear
their young.
Polar bears do indeed accumulate significant
amounts of many organic contaminants.
The maps above show the results of a recent
circumpolar study on which biologists and
conservation managers from Canada, USA,
Greenland, Russia, and Norway collaborated.
The contaminant levels are high compared
with most other Arctic animals. The median
values are 7.2 micrograms PCBs per gram fat,
2.0 micrograms chlordane per gram fat, 0.19
micrograms DDE per gram fat, and 0.15
micrograms dieldrin per gram fat. These levels
are lower than those in seals from highly polluted
waters such as the Baltic Sea.
In six of the regions included in the study,
PCB concentrations in polar bears are in a
range that is known to affect the reproduction
of mink, and in some other areas they are
approaching these levels. Even if mink, when
compared with other animals, are extremely
sensitive to organic contaminants, one cannot
discount the risk that PCBs at current levels
affect the reproductive ability of some polar
bears. One of the areas where levels in polar
bears are highest is Svalbard, but so far it has
not been possible to relate contaminant loads
in individual female bears on Svalbard to their
ability to reproduce.
One concern is that polar bear cubs receive
a high dose of POPs from their mothers’ milk.
The levels of the fat-soluble compounds are indeed
very high in cubs of the year, higher even
than in yearlings. This means that young cubs
are exposed at a period of growth and development
when they may be most sensitive. One study
found that the mortality of young polar bears
on Svalbard was higher than in other areas.
In 1996, two female cubs accompanying
their mother on Svalbard were noted to have
abnormal external genitalia, making them
pseudo-hermaphrodites or hermaphrodites.
The causes behind this abnormal development
are unknown. It could be a rare natural event,
or the result of a hormone-producing tumor in
the mother, or a consequence of toxic sub-
stances.
For PCBs, the levels in adult bears are high
enough to exceed the no-effect and low-effect
levels associated with subtle neurobehavioral
effects in offspring of laboratory animals. At
four of the study sites – Svalbard, east Greenland,
McClure Strait, and eastern Hudson Bay
– they exceed the PCB levels known to affect
kit survival in mink. At other sites they are
close to this limit. Polar bears from east Greenland,
Svalbard, and McClure Strait also have
enough PCBs in their bodies to raise serious
concerns about immune-system effects. Some
bears on Svalbard have levels exceeding those
associated with poor reproduction in seals.
Levels of dioxin-like substances in polar bear
from Resolute Bay, Canada, and Svalbard may
be high enough to affect the immune system.
Polar bears in Canada have increased liver
enzyme activity, which has been correlated with
the levels of coplanar PCBs. There are also
some indications that PCBs have affected the
thyroid hormone and vitamin A levels. These
biomarkers indicate that the diet of polar bears
is probably contaminated enough to affect the
functioning of sensitive hormone systems.
A look at the diet of polar bears supports
the concerns raised by POP levels in the polar
bears themselves. The levels of PCBs and
dioxin-like substances in ringed seal blubber
from all sites exceed environmental guidelines
for protecting wildlife. DDT levels exceed
some of the guidelines.
Arctic fox often scavenge seal carcasses left
by polar bears. They might therefore get just
as much contamination from their food as do
polar bears, and be at similar risk for reproductive
and immune effects. So far, contaminants
in Arctic fox have only been studied on
Svalbard, where their levels are as high or
higher than those of polar bear.
The circumpolar polar bear study makes it
possible to look at geographic variations and
to infer possible underlying causes. There are
89
Persistent Organic
Pollutants
POP levels in polar bear
and Arctic fox.
20
10
0
PCBs CHL
0.6
0.4
0.2
0
µg/g
lipid weight
µg/g
lipid weight
Arctic fox
HCH CBz
clear signs of extensive transport of POPs to
all areas of the Arctic and subarctic. There are
also some notable peaks in concentration. For
example, PCB levels in polar bears are highest
on the east coast of Greenland, on Svalbard,
and in the Arctic Ocean. The Greenland and
Svalbard peaks could be caused by combined
long-range atmospheric transport of PCBs
from North America and from Europe. Another
source could be ice that has received contaminants
from atmospheric deposition as well as
from the Russian continental shelf. Such transport
would also bring PCBs to the Barents Sea
and expose the bear population on Svalbard.
There are parallel observations of high levels
in ringed seals, which is the main diet of the
polar bear.
The peak in the Arctic Ocean is more difficult
to understand. It could be that the food
web in the permanent ice pack has a different
structure than that of coastal and ice-margin
areas, and is based more on the microscopic
animals that live in ice, where they can accumulate
large amounts of contaminants.
The levels of chlordane in polar bears show
a peak in southeastern Hudson Bay in Canada,
which also has the highest DDE and dieldrin
levels. This is probably a sign of atmospheric
transport to this area in summer from eastern
and central North America.
Hexachlorocyclohexanes are highest in
bears from the Bering and Chukchi Seas,
which reflects continuing input from Asia.
Other POPs are generally lower in this region.
Time trends
Is the burden of contaminants in Arctic animals
increasing or decreasing? Will contaminants
used in the past continue to move to the
Arctic even if use is reduced or discontinued?
The results from a few long-term studies of
temporal trends in Arctic biota indicate that
PCB and DDT levels in the Arctic environment
have declined in the past 20 to 25 years, since
the first controls began on DDT and on the use
of PCBs in open systems. Evidence from dated
sediment cores also shows input declines in
subarctic latitudes, as discussed under Lake
sediments have low levels of POPs.
Sharp declines in PCB and DDT levels were
seen in the 1970s and 1980s, and some time
trends indicate continued declines during the
late 1980s and 1990s, whereas others are unclear.
There are no long-term standardized
data sets for the High Arctic. Levels in biota
are extremely variable, and observed levels are
still near the thresholds for biological effects.
These uncertainties and variabilities make it
difficult to speculate about the future, and
reinforce the importance of careful sampling
programs and the need to archive samples for
future analysis.
Less is known about time trends for hexachlorocyclohexane,
hexachlorobenzene, chlordane,
toxaphene, dieldrin, and dioxins and
furans. Of these, hexachlorocyclohexane has
been followed most closely. In air, there was a
nine-fold decrease from 1979 to 1993 in measurements
from the Bering and Chukchi Seas
and from several locations in the Canadian
Arctic Archipelago. In the European Arctic,
however, alpha-hexachlorocyclohexane levels
seem to have declined two-fold, but lindane
levels have increased from 1984 to 1992,
reflecting different regional inputs.
The remainder of this section presents the
results of some specific time-trend studies.
Fish and moss in Scandinavia
show a decreasing contaminant load
Some of the few studies that have been designed
specifically to look at time trends in
biota have been conducted in Scandinavia,
which is probably more representative of the
subarctic than of the High Arctic. The studies
also may not reflect the load in long-lived
species such as polar bear and beluga. Fish
provide the most detailed information.
In Sweden, a study of POP levels from 1967
to 1995 shows a promising trend; see graph to
the left. The levels of DDT, PCBs, dioxin-like
substances, hexachlorocyclohexane, lindane,
90
Persistent Organic
Pollutants
Food-web structure, selective break-down, and stress related to biological effects
The most striking feature of organochlorine levels in Arctic biota is the biomagnification
that occurs in food webs. The highest levels are usually recorded in top predators
in environments with long food chains, such as polar bear, which are third-level carnivores
in the marine food chain. Extremely high contaminant levels have also been
recorded in bottom-dwelling amphipods that feed on the carcasses of dead animals.
This can be contrasted to the short terrestrial food chain, where wolves are only firstlevel
carnivores, and have correspondingly lower contaminant loads.
Many Arctic animals are opportunistic feeders, and may occupy more than one
position in the food web. Walrus feeding on seals have much higher contaminant loads
than walrus that feed on mussels. Also, changes in food-web structure can affect
contaminant intake. Lake Laberge in Canada illustrates how overfishing and higher
nutrient input have changed feeding habits of lake trout, resulting in elevated contaminant
levels.
Not all contaminants biomagnify. In fact, the chemical signatures in top-level
predators, such as the polar bear, reveal that some compounds are effectively degraded
along the food chain. For example, polar bears can break down DDT, so that their
DDT levels are sometimes lower than those of ringed seal, their main food source.
Much of the contaminant load is stored in fatty tissues. This fat is used for energy.
When a substantial proportion of the fat is used up, as happens in starvation periods,
the concentration of contaminants in the remaining fat increases, with a corresponding
increase in the concentration in blood and in vital organs. There are some indications
from predatory birds that the combination of a high body burden of contaminants
and prolonged periods of starvation may contribute to the death of an animal.
7 0.12
0.10
0.08
0.06
0.04
0.02
0
6
5
4
3
2
1
0
1970 ’75 ’80 ’85 ’90 1995 1970 ’75 ’80 ’85 ’90 1995
Concentration in pike, ng/g lipid weight
PCBs
HCH
HCB
DDT
Time trends in pike from
Lake Storvindeln,
Sweden.
and hexachlorobenzene have all declined, in
lakes as well as in the Baltic Sea. The decline of
PCBs is further verified in a Finnish time trend
study.
The start of the declines in PCBs and DDT,
in the 1970s, coincides with decisions to
reduce environmental pollution, and shows the
value of such political efforts. Even in remote
areas of Arctic Sweden, the sudden decline in
the Russian economy in the late 1980s shows
up in the data, as do reductions in the production
and use of pesticides. As a reminder of the
consequences of renewed use of pesticides,
spraying of DDT in the former East Germany
in the summers of 1983 and 1984 caused readily-detectable
increases of the contaminant in
Swedish lakes.
PCBs continue to be a concern. PCB levels
have not declined as fast as those of pesticides.
This indicates a continuing release of PCBs
into the environment, and thus a need to take
action against potential sources.
In Norway, moss has been used to look for
time trends in the deposition of PCBs. In coastal
areas, the mean concentration fell from 21.2
nanograms per gram in 1977 to 6.9 nanograms
per gram in 1990. Because moss takes
up all its nutrients from the air, this decline
mirrors a decrease in atmospheric PCB concen-
trations.
Marine animals
show a varied geographic picture
Results from monitoring marine animals provide
good evidence for declining concentrations
of the major organochlorines in both the
European and the North American Arctic. For
example, seabirds breeding in northern
Norway had 60 percent lower levels of hexachlorobenzene,
85 percent lower levels of
DDE, and 78 percent lower levels of PCBs in
the period 1983 to 1993 compared with 1979
to 1981.
In the Canadian High Arctic, PCB and DDT
levels in eggs of migratory seabirds declined
from 1975 to 1993, mostly in the late 1970s
and early 1980s. This decline may reflect an
overall reduction in organochlorine levels in
the North Atlantic. The decline is not uniform,
however. In one of the birds, the ivory gull,
PCB and chlordane levels in the eggs have
increased.
Declines in POPs in seals and whales from
the western Canadian Arctic are not as steep
as those observed in seabirds and whales from
eastern Canada. From 1972 to 1991, PCB concentrations
declined five-fold and DDT concentrations
three-fold in marine mammals
from the western Canadian Arctic.
Over the past 10 to 12 years, seals and walrus
from Eastern Canada and Greenland have
shown no declines in contaminant levels, nor
have there been any declines in DDT, PCBs,
chlordane, or toxaphene in female ringed seal
or in male narwhal from Lancaster Sound
from the mid 1980s to the early 1990s.
PCB levels in Arctic fox from Svalbard
seem to have been similar in the 1970s and
in the 1980s.
Summary
All persistent organic pollutants in AMAP’s
monitoring program have been found in the
Arctic. The levels are generally lower than in
temperate areas, but for several substances they
are still in concentration ranges in which effects
on some animals are expected. These include
reproductive effects in birds from DDT and in
some marine mammals from PCBs and dioxinlike
compounds. Current concentrations in several
Arctic species are also close to or above
thresholds known to be associated with immunosuppressive
and neurotoxic effects. The most
vulnerable animals are those high in the food
web, such as polar bear and birds of prey.
Biomagnification is one major factor contributing
to the high levels and biological effects of
persistent organic pollutants in Arctic animals.
Another biological pathway is via migratory
birds that overwinter in polluted environments.
The major source of persistent organic pollutants
in the Arctic is long-range transport via
air currents, as demonstrated by monitoring of
air concentrations. There may also be significant
sources of some contaminants, such as
PCBs, DDT, and hexachlorocyclohexane,
within the AMAP region, but these are not
well documented. Data from river water and
sediments indicate a substantial input from
Russian rivers into the Arctic marine environment,
but these data must still be verified.
Available data point to some geographic
trends. In general, the levels of PCBs and DDT
seem to be higher around Svalbard, in the
southern Barents Sea, and in eastern Greenland
than in, for example, the Canadian High
Arctic. Levels of hexachlorocyclohexane appear
to be higher in the Canadian Arctic than in
Eurasia. Very limited data from Russia and
Alaska were available for this assessment. The
lack of circumpolar data limits our understanding
of sources, transport pathways, and
mechanisms for focusing contaminants. The
role of sea ice in transporting contaminants
and then releasing them during melting warrants
further investigation.
A few studies of time trends point to a
decreasing load of PCBs and DDT in subarctic
regions from the 1970s to the 1980s, after use
of these substances was restricted or banned.
However, it is not clear whether this decline
has continued from the 1980s to the 1990s, or
if similar declines have occurred in the High
Arctic. The decline seems to be slower for
PCBs, which may indicate continued low-level
leakage to the environment from unknown or
poorly studied sources.
91
Persistent Organic
Pollutants