In the field of public health, air pollution is a well-known phenomenon, which has been studied for long and becomes of major importance in our contemporary world parting from a series of episodes which happened in industrial countries during the first part of the 20th century. The cases in the Meuse Valley (Belgium) in 1930, in Donora (Pennsylvania, USA) in 1948 and, above all, the catastrophe of London, in December 1952, are probably the most outstanding and characteristic (Ware et al., 1981). These exceptional situations resulted in an increase of mortality and morbidity which left no doubt to the fact that high levels of air pollution were causally associated with an increase in early deaths