For as long as kids have been surreptitiously whisking their vegetables under the table, mother have been scolding them to eat carrots for their vision and swallow spinach so they'll grow up big storng. Parent still feeding their children propaganda alongside the parsnips had best hide this article from their offspring. For there is growing concern among scientists that pesticide residues in some foods, especially certain fruits and vegetables, present serious hazard. A major study by environmental group Natural resources Defense Council (NRDC), slated for release next month, is expected to conclude that America's children are being poisoned at their dinner tables. Says Jay Feldman of the National Coalition against the Misuse of Pesticides, "The food system is overly, unnecessarily contaminated and children are in the line of fire.