[Potable water in Local Health Area 12 from 1980 to 1987].

This research work deals with the problem of the pollution of both public and industrial water supplies in a local health authority area (U.S.S.L.) in Lombardy. This is an area of approximately 120 square kilometres which, for the most part, does not as yet have a public sewage system purification plant. As a result, almost all effluent enters the local watercourses which have developed physico-chemical characteristics similar to those of sewage, thus creating very serious health risks for the inhabitants of the area. Our study deals especially with the hydrological characteristics of the area which possesses two water-tables, one above the other. The lower of these two water-tables has a particularly large supply in the source areas of the rivers. Following this our study presents data concerning the wells in the area, their position, methods of excavation, depth, stratigraphy and capacity of water-supply. Since 1980, all wells have had regular four-monthly or six-monthly microbiological and chemical tests. Special attention has been paid to the levels of ammonia, nitric and nitrous acid, pH, sulphates, electrical conductivity, chlorides, chromium and chlorate solvents. During 1986-87, one investigation was carried out on the presence of Cu, Pb, Ni, F, Cd, Al, hydrocarbons and tensioactive substances. The main pollutants were discovered to be chlorohydrocarbons and nitrates. The chlorohydrocarbons come from textile factories and metallurgical and mechanical industries which discharge these substances into the drainage system either as the result of accidents of because or inadequate depuration. The source of the nitrates is, for the most part, domestic although a small proportion is also due to agriculture. As a result of the discovery of this pollution of the water-tables, a programme of preventive checks has been introduced for all the industries which use chlorate solvents. The purpose of these checks is to identify the methods of use and of disposal of these substances. A more satisfactory discharge of industrial effluent has been achieved by at least some of the firms in the area with a consequent reduction both in illegal discharge and in pollution of the water-tables.