Environ. Sci. Technol. doi:10.1021/es702919n (2008)

Credit: HEIDI GEISZ

Adélie penguins are taking in decades-old stores of the toxic pesticide DDT being released by melting Antarctic ice. Post-1970 bans on the pesticide reduced levels in other seabirds, which store the toxin in their tissues — but melting of DDT-laced glaciers along the western Antarctic Peninsula, hastened by rising temperatures, has meant continued exposure for the penguins.

Heidi Geisz of the College of William and Mary in Virginia and co-workers tested for the chemical in Adélie carcasses and eggs collected from Palmer Archipelago on the Peninsula and Ross Island in east Antarctica. Although worldwide use of DDT has dropped over 90 per cent since its 1970s peak, the amount concentrated in Palmer Island Adélie penguins has changed little in that time, they found.

Whereas eastern Antarctic birds contained only DDE, a metabolic product of DDT that lingers in the food chain over time, those from Palmer Island also had a fresh source of DDT — most likely pesticide that hitched onto pole-bound particles and was buried in the growing glaciers of the mid-twentieth century. The one to four kilograms of DDT per year now leaking into the ocean is unlikely to harm the penguins, say the authors, but it could be accompanied by more dangerous chemicals.