To the Editor: Because of the infestation by the Mediterranean fruit fly in areas of states with considerable fruit production (California and Florida) and the obvious risk of rapid reproduction and spreading of the flies, with resultant economic loss, state authorities decided on aerial spraying of infested areas with malathion. In some districts, spraying had to be done repeatedly, and although it is known that malathion is rapidly metabolized, there was concern that some of this chemical might "spill over" into breast milk and thus expose infants to potentially harmful effects.We have analyzed milk samples from nursing women living . . .