Airborne mineral fibre concentrations in an urban area near an asbestos-cement plant.

Ambient air concentrations of asbestos and total mineral fibres were measured during the period June-July 1985 at several locations near a large asbestos-cement factory located in the proximity of a northern Italian town. Measurements of the number and type of fibres were made by means of analytical scanning electron microscopy and energy-dispersive X-ray analysis (SEM-EDXA), essentially according to the RTM2 reference method of the Asbestos International Association. Total mineral fibre concentrations (longer than 5 microns) ranged from below detection limit (D.L., i.e. 0.4 fibres per litre (f/1] to 227 f/1 (single value); mean values ranged from 1.3 to 74.0 f/1. However, elemental microanalysis (EDXA) showed that about 65% of fibres were sulfate fibres, 20% were aluminium silicates or other silicates, and only 15% were asbestos fibres (mainly chrysotile and tremolite-group amphiboles). Asbestos concentrations (fibres more than 5 microns in length) were in the range of less than D.L. to 19.1 f/1, mean values ranging from less than D.L. to 11.1 f/1. The results obtained showed large differences in day-to-day concentrations, suggesting that they were affected by the rate of production in the plant and by weather conditions. In particular, wind direction and distance from the source appeared to be of major importance since the highest asbestos fibre concentrations were mostly found at points closer to the source and downwind. When the distance from the source was increased, other local factors appeared to be determining. In addition, the large proportion of non-asbestos mineral fibres and elongated sulfate (or sulfur-containing) particles clearly indicates major contributions from other sources, such as local pollution and natural soil erosion.