Narrator: This is Science Today. A generation after it was banned in the United States and other industrial democracies, levels of the pesticide DDT are way down and wildlife is recovering, according to researcher Wally Jarman of the University of California, Santa Cruz.

Jarman: The big problem now, and it is a big question, is how much DDT is being used in other countries. We know that a lot is used in India, a lot is used in China, there may be a lot used in Russia and the republics, but we really don't know how much.

Narrator: And it's not that easy to find out. Manufacturers are reluctant to release information, and measurements can be misleading.

Jarman: If you measure the amount of DDT in the air right here, there'd be a fair amount. It would surprise you how much is there, that it's traveling around the globe. So it's not that easy to just go to Russia or China and take a measurement and say OK, it's all from this factory. Because you can go to very pristine areas like the Arctic or the Antarctic and still find DDT residues.

Narrator: For Science Today, I'm Steve Tokar.