Estimates of past exposure to respirable man-made mineral fibres in the European insulation wool industry.

Airborne fibre concentrations measured in the European insulation wool plants during 1977–1980 and 1984 have been revised to take account of the harmonization of counting levels between European laboratories. These data, together with dust emission measurements on old and new products, have been used in conjunction with data from a previous study of the technical history of each rock wool/glass wool plant to derive a model of past exposure at each plant. Account is taken of the changes in production identified as having a potential effect on airborne fibre levels: nominal fibre diameter, addition of oil, changes in the ventilation or production rates and the use of labour-intensive batch production methods. The model predicts mean airborne fibre concentrations for rockwool plants of about 1–2 Fr ml −1 during the early technological phase with levels of about 10 Fr ml −1 for the dustiest work. Current exposure levels are at least one order of magnitude lower, Corresponding model estimates for the glass wool plants during the early technological phase indicate that the mean airborne fibre levels then were little different from current levels (about 0.1 Fr ml −1 or less).