For the past 30 years ago, the use of DDT as a freely used pesticide has diminished worldwide. One of the first successful campaigns against the chemical was based on its effects on birds. So, it came as a surprise to scientists that Adelie penguins in the Antarctic have the same levels of DDT in their bodies today as they did 30 years ago.  

Heidi Geisz, a marine biologist at the Virginia Institute of Marine Science and the leader of the study of DDT levels in penguins, says that an accumulated store of the pesticide within melting Antarctic glaciers is flowing into the nearby ocean, where it builds up within penguin fat and eggs. Geisz’s discovery of persistent DDT levels in Adélie penguins runs counter to trends seen in studies of Arctic seabirds, whose falling DDT levels reflect the worldwide decline in DDT use. The researchers note they didn’t find DDT or DDT byproducts in Antarctic air, snow, ice, or seawater, only in glacial meltwater.

With warming trends in the Antarctic melting glaciers faster, Geisz worries that chemicals more harmful to animals, like the flame retardant chemicals PCB and PBDE, will be released into the ocean.