- Evidence that the health of polar bears is being damaged
by chemicals has been reinforced by new Arctic research.
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- The findings show biological changes in the hormone and
immune systems of the bears are related to the levels of toxic contaminants
in their bodies.
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- WWF, the global conservation campaign, says the data
confirms the findings of other research in the last four years.
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- It says the chemicals may affect the bears' behaviour
and breeding, and make them more vulnerable to infection.
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- The research is published in two academic journals: the
Journal of Toxicology and Environmental Health, and Environmental Health
Perspectives.
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- It was conducted by international teams of scientists
in Canada and on Spitzbergen, the main island of the Svalbard archipelago
in the high Arctic. WWF is publicising the findings to support its campaign
for more stringent laws to control chemicals.
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- The substances blamed for the damage are PCBs (polychlorinated
biphenyls) and pesticides: the higher their level in the bears, the lower
the level of antibodies found in their blood.
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- WWF says: "Toxic chemicals were also correlated
with the steroid hormone cortisol and thyroid hormone levels in Svalbard
polar bears.
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- "Reduced levels of antibodies leave bears more susceptible
to infection. Altered hormone levels could result in a wide range of negative
health impacts, such as development, behaviour, and reproductive problems."
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- Unable to cope
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- Dr Andrew Derocher, who has long experience in studying
the bears' contamination, said: "The studies conducted on polar bears
over the last few years all conclude that these animals are negatively
affected by chemical pollution.
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- "Most polar bears probably have several hundred
man-made chemicals in their bodies and they have never evolved mechanisms
to deal with them.
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- "The unintentional tinkering with the hormone and
immune system of a polar bear is unlikely to be good for them."
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- WWF says that although the contaminants found in these
studies are no longer widely used, they are slow to break down in the environment
and can remain in water, ice, and soil for many years.
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- Brettania Walker of WWF's Arctic programme said: "Other
contaminants, with similar properties, continue to be used on a day-to-day
basis in manufacturing processes and products throughout the world. In
2000 scientists on Svalbard said more than 1% of the islands' bears were
hermaphroditic, showing the reproductive organs of both sexes.
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- PCBs were manufactured for use in electrical equipment,
and although many countries have now banned them, there is a reservoir
of the chemicals that has escaped into the environment.
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- © BBC MMIV http://news.bbc.co.uk/2/hi/science/nature/3645112.stm
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