A simple sedimentation method for quantifying the dispersion of asbestos fibre bundles from asbestos-containing materials

The present study is a follow-up of a previous research, in which a sedimentation method was proposed to measure the dispersion of fibres (primary pollution), constituted by coarse asbestos bundles, from asbestos-containing materials. The method, measuring the asbestos amount deposited on the sedimentation instrument, was improved introducing the dispersion staining method to the standard PCOM analysis, combined with the weight calculation of the concentrations of asbestos per surface unit per time unit. The optimal sampling time was defined in 25-30 days without rain, extending the sampling time established in the previous investigation. The sampling efficiency was improved introducing a new adhesive treatment of the microscopic slides (85% stearyl alcohol, 15% octyldodecan) and a dimensional cut restricting the counting method only to the fiber bundles with diameters larger than 2 µm. The optimal instrumental placing distance was defined in 50 cm (vertical) and 0 cm (horizontal) from the dispersion sources (i.e. asbestos-cement roofs etc.). The influence of the strength and main direction of winds on the dispersion phenomenon was also evaluated. This low-cost sedimentation method, now available for practical use, can play an important role in the field of environmental primary pollution controls.