Fibre-years, pulmonary asbestos burden and asbestosis

The relations between cumulative asbestos fibre doses at the work-places and asbestos burden of the lung evaluated by lung dust analyses have been tested on 3 different groups of patients of the German Mesothelioma Register: 1. total collective (n = 366), 2. collective without elevated asbestos burden of the lungs (n = 193), 3. collective with asbestoses/minimal asbestoses (n = 64). The relations between the above mentioned parameters are in general only weak. The limit value of > 25 fibre-years is found in 19.6% of persons without increased pulmonary asbestos burden. In spite of reaching or exceeding the cumulative doses of 25 fibre-years, 24% of the whole collective also show no elevated asbestos-concentrations in their lung tissues. By contrast, 42% of patients with asbestos-associated lung fibroses do not attain 25 fibre-years at their work-places. Considering our data it is doubtful that the postulated limit value of 25 fibre-years can be an adequate parameter for the evaluation of asbestos-associated lung fibroses.