Assessment of airborne mineral wool fibres in domestic houses

This report describes a series of measurements made to assess the concentration of airborne mineral wool fibres (denoted as MMMF in this report) in domestic houses. Ten houses were selected for monitoring, five where new insulation was being installed and five where existing insulation was being disturbed. In the houses with new insulation samples were collected prior to installation, on the day of insulation and on two occasions afterwards. The samples were analysed by either phase contrast optical microscopy (PCOM) or by scanning electron microscopy (SEM). On each day a sample was collected to assess the airborne inspirable mass concentration. In addition, measurements of the bulk fibre characteristics and settled dust were made. A similar programme was used to obtain samples from houses with existing insulation, where monitoring was carried out prior to disturbance of the mineral wool and during major and minor disturbance.Within the lofts the personal airborne fibre concentrations were approximately 1 fibre/ml during insulation and generally less than 0.1 fibres/ml when existing insulation was disturbed. The levels inside the houses were much lower, and in these situations only the SEM measurements are a reliable indication of airborne mineral wool concentrations. In new houses the levels of mineral wool were approximately 0.01 fibres/ml and in the old houses the levels were generally not detectable, i.e. less than 0.005 fibres/ml.Comparison of the results from a small number of samples analysed by SEM and transmission electron microscopy (TEM) showed that both techniques produced comparable results.Within 24 hours of insulation or disturbance of mineral wool the concentration of airborne MMMF was at or below the detection limit of 0.005 fibres/ml. Background levels from pooled data or high volume samples indicated that actual levels were about 0.0002 fibres/ml or less.