Epidemiological significance of mineral fiber persistence in human lung tissue.

For the experimentalist, mineral fiber persistence may provide clues to disease mechanisms, for the epidemiologist, to the measurement of exposure. Qualitatively, this can be valuable when unsuspected exposures have been demonstrated as, for example, MMMF workers exposed to amosite or chrysotile workers to tremolite. Quantitatively, the potential of lung burden analyses to assess lifetime mineral fiber exposure has yet to be achieved with confidence. The difficulties are 2-fold, the first related to sampling and the second to the dynamics of biopersistence. Until some noninvasive method is found to identify and quantify numerically inorganic fibers in human tissue during life, epidemiological studies must depend on lung samples obtained at autopsy or thoracic surgery. This source is inevitably subject to seriously large and indefinable bias of various kinds. Of equal importance is the present uncertain state of knowledge concerning factors that determine what is present in the lung at any time. These determinants clearly include the dimensional features of airborne environmental particulates and characteristics that affect their durability in tissue.