Pesticide DDT shows up in Antarctic penguins
Pastor Dale Morgan
Pesticide DDT shows up in Antarctic penguins*
09 May 2008 22:27:43 GMT
Source: Reuters
By Deborah Zabarenko, Environment Correspondent
WASHINGTON, May 9 (Reuters) - The pesticide DDT, banned decades ago in
much of the world, still shows up in penguins in Antarctica, probably
due to the chemical's accumulation in melting glaciers, a sea bird
expert said on Friday.
Adelie penguins, known for their waddling gait and a habit of nesting on
stones, have long shown evidence of DDT in their fatty tissues, although
not in enough concentration to hurt the birds, according to Heidi Geisz
of the Virginia Institute of Marine Science.
But researchers were surprised to see that the level of the pesticide in
Adelies' fat had not declined, even after DDT was banned for exterior
use in the 1970s in the United States and elsewhere.
First noted in 1964, while the chemical was still widely used, the
amount of DDT found in Adelie penguins rose in the 1970s and has stayed
stable since then, Geisz said in a telephone interview.
In findings published in the journal Environmental Science & Technology,
Geisz and her colleagues noted that persistent organic pollutants like
DDT accumulate and become concentrated in the Antarctic ecosystem.
"DDT, along with a lot of other of these organic contaminants, actually
travel through the atmosphere ... toward the polar regions by a process
of evaporation and then condensation in cooler climates," Geisz said,
explaining this is how the pesticide got deposited in Antarctic glaciers.
DDT declined dramatically in Arctic wildlife over the last decade, while
the amount of the chemical in Antarctic Adelies stayed stable, the study
said.
DDT was easily detectable in glacier melt water, Geisz said.
FOOD CHAIN
Adelies feed off tiny creatures called krill that live in melted glacier
water, and DDT is transmitted up the food chain directly to the penguins.
There is not enough of the chemical to harm the birds, but it is
measurable in samples of penguin corpses and their abandoned eggs, Geisz
said.
Some kinds of birds that ingest DDT, especially birds of prey like the
American bald eagle, produce eggs with extremely thin shells which are
easily crushed by adult birds. Geisz said this has not been demonstrated
to be the case with sea birds.
A more pressing issue for the Adelie penguins that breed on the
Antarctic Peninsula is encroaching climate change, she said. The
peninsula, which stretches north toward South America, has been warming
much faster than the rest of the continent.
Warming on the peninsula means "we see more snow and more moisture and
these (Adelie) eggs end up getting soaked and frozen," Geisz said. "It
allows opportunities for people like me to study the eggs, but it's not
necessarily ideal for the penguins."
Originally developed as a powerful multi-species pesticide, DDT was used
in World War Two to clear South Pacific islands of malaria-causing
insects for U.S. troops and in Europe as a de-lousing powder. The United
States banned the chemical in 1972. The World Health Organization
approved it in 2006 for use indoors to fight malaria.
(Editing by Eric Beech)