The territory of the megapolis is a zone of interaction of a large number of anthropogenic factors that must be considered when determining the quality of the environment, and most importantly in the allocation of pollution sources. Allocation of the general background of local pollution sources that have not yet made their significant contribution to the overall condition of the territory, but nonetheless potentially dangerous in the future, is extremely important practical problems. The article describes the methods of handling information on contamination of such local-zones and features a non-uniform accounting information. Refs 5. Fig. 1. Tables 2.