Polar bears in a frozen wilderness.
A pure, unpolluted environment. Wrong! Recent scientific research
shows that, in some areas, polar bears are exposed to high levels
of poisons and pollutants.
Persistent organic pollutants (POPs) include a wide range of poisonous
substances such as heat resistant chemicals like PCBs, industrial
by-products such as dioxins and furans which come from waste incineration;
and pesticides like DDT, dieldrin and lindane. In addition to staying
in the environment for a long time, POPs are a special concern because,
as one animal eats another, these poisons are concentrated in fat
and stored in vital organs in the animal that has eaten poisoned
prey. As a top predator, polar bears are exposed to high levels
of such pollutants through their food.
Due to the direction of prevailing winds and ocean currents, these
substances are concentrated in parts of the Arctic. Most POPs are
banned, but they are still used widely in Russia, eastern Europe,
and Asia.
Long-range POPs currently represent the most serious pollution-related
threat to polar bears.
Bears with high levels of some POPs have low levels of vitamin A,
thyroid hormones, and some antibodies. These are important for a
wide range of biological functions, such as growth, development,
reproduction, behavior, and the ability to fight off diseases.
Newborn cubs are especially vulnerable to these pollutants. In some
areas, the mother's milk on which they are totally dependent for
growth and development, contains particularly high concentrations
of these chemicals. The milk can actually poison the cubs, leading
to lower survival rates.
Pseudohermaphroditism, a long word meaning that females have partially-developed
male sexual organs, has been observed in 1.5 per cent of the polar
bears sampled on Svalbard in recent years. Scientists believe this
could be the result of long-range pollutants.
There are also reasons to worry about other pollutants. A wide range
of new, man-made persistent substances are making their way to and
are being concentrated in the Arctic. The effects of these are still
unknown. In addition there are other pollutants that we know about,
but that we are not studying due to lack of resources. These include
both POPs and other contaminants, such as stain repellents known
as PFOS, and brominated flame retardants. These may have similar
impacts on polar bears as those already documented. |
The figure shows concentrations of PCB (polychlorinated biphenyl) and
HCH (hexachlorocyclohexan) in adult female bears. At Svalbard PCB
levels measured in fat are approximately five times higher than in
blood from the same animal. It this relationship is the same in other
areas, alarmingly high fat PCB concentrations can be expected in
polarbears in Russia.
Concentrations of POP's in polar bear milk of females with cubs after
emerging in March from dens in the Cape Churchill area, Hudson Bay. The
data are grouped according to whether the female still had her cubs the
following fall, or had lost them.
Source: Arctic Monitoring and Assessment Program.
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