Narrator: This is Science Today. The best way to handle an oil spill at sea is to clean it up, right? Not necessarily. Chemist Ron Tjeerdema of the University of California, Santa Cruz says that cleanup chemicals called oil dispersants just move the problem from one part of the ocean to another.

Tjeerdema: What oil dispersants basically do is they remove oil from the surface of the water and drop it into the water column. An oil spill can be several miles wide, several miles long but it's really only a few millimeters thick. And it's more or less a coating of Saran Wrap on the water, basically. And so for most organisms that live 10, 20, 30 meters below it's not of consequence, for instance for fish.

Narrator: But a dispersant removes the oil from the surface, superficially cleaning it, and sends the toxic gunk down below.

Tjeerdema: And by doing that, then it's right there for fish then to be exposed to.

Narrator: Which can lead to the terrible choice of not using a dispersant and poisoning birds and marine mammals at the surface, or using it and poisoning fish in the water. For Science Today, I'm Steve Tokar.