Problems in assessing airborne man-made mineral fibre concentrations in relation to epidemiology

The results of airborne dust measurements undertaken in the European MMMF manufacturing industry in conjunction with a retrospective epidemiology study were reported at a WHO conference in 1982. Subsequently, a reference scheme was instigated to develop reference evaluation procedures for use in epidemiology and to harmonise interlaboratory differences using these methods. These developments have resulted in an increase in the reported fibre concentrations for the above study by approximately three times. Estimates of the average airborne respirable fibre concentrations for combined occupational groups in glasswool manufacture ranged from <0.01 fibres/ml to 0.10 fibres/ml and from 0.02 fibres/ml to 0.14 fibres/ml in the rockwool plants. Information about the technical history of the factories has been obtained and the validity of using current fibre concentrations to estimate workers' past exposure is discussed. Three changes in production have been identified as having a potentially important effect on fibre levels: nominal fibre size, addition of oil to MMMF and labour intensive batch production techniques. It has been estimated that changes in these parameters may have reduced fibre levels by up to ten times. Based on the plant technical histories the production at each factory has been divided into three phases for use in the epidemiological analysis described in another paper at this symposium.