The insecticide DDT, banned decades ago by most countries, continues to seep into Antarctic ecosystems, say researchers who found trace elements of the chemical in Adélie penguins.
A team of researchers led by Heidi Geisz, a marine biologist at the Virginia Institute of Marine Science in Gloucester Point, report that the DDT found in the penguins' fatty tissues had not declined over the past 30 years. Her team's findings, published in Environmental Science & Technology, a peer-reviewed journal published by the American Chemical Society, suggest that airborne DDT particles from the 1960s had become trapped in Antarctic glaciers, which were expanding at the time. Now, as the ice sheets melt, the chemical is being released back into the environment.
DDT makes its way into the birds via tiny creatures called krill, a staple of the Adélie penguin diet that lives in glacial meltwater. The short food chain means that the contaminated water is "an almost direct delivery system of DDT to birds and other large animals," according to Ms. Geisz.
Fortunately for the penguins and their offspring, the birds were not found to contain harmful levels of the pesticide. But Geisz worries that the presence of DDT in the penguins could indicate that other frozen pollutants could also be affecting the penguins.
"DDT is not the only chemical that these birds are ingesting and it is certainly not the worst," Geisz told the New Scientist magazine, which reports that she plans to examine other pollutants that may be transmitted from melting glaciers to birds.
DDT was used widely in the 1940s and 50s as an agricultural pesticide. It also played a role in the elimination of malaria from the developed world and parts of the developing world. Beginning in 1957, biologist Rachel Carson documented how uncontrolled use of the pesticide was leading to the deaths of birds, particularly raptors such as the peregrine falcon and the American bald eagle, and was harmful to humans. Her 1962 book, Silent Spring, eventually led to the US government phasing out the chemical. Other countries followed suit, and today the chemical is used only in malaria eradication programs.