Good old tap water will go a long way toward washing pesticide residues off your fruit and vegetables, but “getting it down to zero is not feasible, ever,” said Dave Stone, a toxicologist who is the director of theNational Pesticide Information Center, a cooperative effort between Oregon State University and the Environmental Protection Agency. While washing can reduce pesticide residues on the surface, it cannot eliminate pesticides that are absorbed by the roots into the very tissue of the fruit or vegetable.

Scrubbing with a vegetable brush helps, Dr. Stone said, but using a store-bought veggie wash might not: A 2000 study by the Connecticut Agricultural Experiment Station found that rinsing lettuce, strawberries and tomatoes under tap water for 60 seconds worked just as well as using a commercial vegetable wash to significantly reduce pesticide residues. Using a veggie wash might even backfire, Dr. Stone said, because detergent residue could be added to fruits with porous outer layers.

The best way to wash is to place the fruit or vegetable in a colander and run water over it, rather than just dunk it in a bowl. “The force of the running water will drive off residues,” Dr. Stone said. Peeling also helps get rid of pesticide residues in the skin.

The Environmental Working Group’s so-called Dirty Dozen and the Consumer Reports Always Buy Organic list, both of which are based on data from the federal Department of Agriculture, which tests fruits and vegetables after they have been washed, include items deemed to have relatively higher pesticide loads. Both lists include strawberries, nectarines and American-grown apples. If you’re considering buying organic, you might put these items at the top of your list.