The effect on public health of the electromagnetic radiation generated by power lines is a reason of worldwide controversy. Although the epidemiological evidences are not conclusive there is a conscience on the potential risk that could represent. Some Spanish city councils have put a term to the electric companies to modify the eIectric transport lines close to housing areas. The studies on the electromagnetic radiation generated by power lines have a great incidence in the environmental studies. In this scope, the Department of Geoquimica, Petrologia i Prospecció Geolögica of the Barcelona University, in collaboration with NADREC Company carried out a study for the city council of Montcada i Reixac about the electromagnetic fields generated in the electric lines crossing this municipality.