[Atmospheric asbestos pollution in the urban environment: Rome, Orbassano and a control locality (II)]

To complete our previous study which evaluated by TEM the atmospheric concentrations of asbestos in the urban areas of Milan, Casale Monferrato, Brescia, Ancona, Bologna and Florence, the concentrations measured in Rome, Orbassano and in two mountain test locations, one with serpentine rock (Valle di Susa) and the other with granitic rock (Adamello), are now reported. Compared with the towns in northern Italy, which had already shown decreasing pollution levels from Casale Monferrato to Milan, Brescia, Ancona, Bologna and Florence, the levels measured in Rome were extremely low, about ten times lower than those measured in Florence, which were in turn ten times lower than those measured in Milan. In Orbassano the levels near serpentine quarries were slightly higher than the geologic background values. The geologic background level in Valle di Susa was approximately 1 fibre/litre (> 5 microns) and 2.5 fibres/litre (total fibres); asbestos fibres were totally absent in the mountain area with granitic rock. The clearly decreasing values of pollution starting from the northern cities down to Rome lead to the exclusion of motor vehicle traffic as one of the "primary" sources of fibre dispersion. In fact, traffic becomes significant in producing pollution only in the presence of other dispersion sources since it gives rise to "secondary" pollution consisting of ultra-thin fibres through grinding of coarse fibres dispersed from other sources and sedimented on the ground. The authors attribute the main responsibility in maintaining comparatively high concentrations of asbestos fibres in the urban areas of northern Italy to weathered asbestos-cement coverings which act as "primary" sources.