DDT is an effective, but harmful pesticide that was banned in the U.S. in the 1970s. Throughout the world it is nowadays very rarely used, except for places with malaria outbreak issues. It was never used in Antarctica, which is kind of obvious since the flightless midge is like the only Antarctic bug and it is not a nuisance bug. It has, however, gotten to Antarctica and has been found in penguins.
Here is an article I read about DDT being found in penguins. The article discusses how the use of DDT has slowed, but the amount of DDT found in penguins has remained the same. It also mentions that the melting of glaciers is causing DDT to be rereleased into the atmosphere having been locked away in the ice. The DDT is absorbed by microbial organisms, which the krill eat and in turn the Adelie penguins (that is the penguins used in the study discussed in this article) eat the krill. It is disturbing to see that the DDT is basically being reintroduced to the environment through ice melting and not from it being used, however, at least it does not currently appear to be affecting the penguins.