Antarctic Penguins Reveal Steady DDT Levels

May 5, 2008 -- Although use of the pesticide DDT was banned in the Northern Hemisphere in the 1970s, and DDT levels in the Arctic have declined steadily since then, new measurements show that DDT levels in Antarctic Adélie penguins have remained constant.

"These levels are not high enough to be of concern," said lead researcher Heidi Geisz of the Virginia Institute of Marine Science in Gloucester Point, Va. But the presence of DDT suggests that other contaminants, some of which might have greater effects on seabirds, might be moving in the environment in similar ways, she added.

The researchers blame melting glaciers for the continuing supply of DDT -- deposited in the ice in past decades -- to the environment, where it is taken up by phytoplankton and moves up the food chain, accumulating in the fat of animals at the top, such as Adélie penguins.

"There wasn't any DDT coming in on the air, or in the snow, or in the sea ice," Geisz said of other team members' environmental measurements, "but when they looked at the melt water, it was easily detectable there."

The team measured DDT levels in the fat of 12 penguins they found dead and in 27 eggs found ruined at two study sites in the Antarctic. They compared these findings with measurements from the 1960s and 1970s and found no statistical change in the combined levels of DDT and its breakdown product, DDE.

"It's not conclusive, given our sample size," Geisz noted, "but it appears that these levels aren't declining."