That residues of pesticide and other contaminants in the total environ­ ment are of concern to everyone everywhere is attested by the reception accorded previous volumes of "Residue Reviews" and by the gratifying enthusiasm, sincerity, and efforts shown by all the individuals from whom manuscripts have been solicited. Despite much propaganda to the contrary, there can never be any serious question that pest-control chemicals and food-additive chemicals are essential to adequate food production, manu­ facture, marketing, and storage, yet without continuing surveillance and intelligent control some of those that persist in our foodstuffs could at times conceivably endanger the public health. Ensuring safety-in-use of these many chemicals is a dynamic challenge, for established ones are continually being displaced by newly developed ones more acceptable to food technologists, pharmacologists, toxicologists, and changing pest-con­ trol requirements in progressive food-producing economies. These matters are of genuine concern to increasing numbers of govern­ mental agencies and legislative bodies around the world, for some of these chemicals have resulted in a few mishaps from improper use. Adequate safety-in-use evaluations of any of these chemicals persisting into our food­ stuffs are not simple matters, and they incorporate the considered judg­ ments of many individuals highly trained in a variety of complex biol­ ogical, chemical, food technological, medical, pharmacological, and toxi­ cological disciplines.

Polychlorinated biphenyls: Occurrence and biological effects.- DDT residues in marine phytoplankton.- The regulation of pesticides in Argentina.- The possible importance of transfer factors in the bacterial degradation of herbicides in natural ecosystems.- Guidelines for environmental study of pesticides: Determination of bioconcentration potential.- Evaluation of human health hazards on use of dichlorvos (DDVP), especially in resin strips.- Comment on the distinction between hazard and safety in evaluation of human health hazards on use of dichlorvos, especially in resin strips.