[Findings in the bronchopulmonary system of workers employed in the industrial production and processing of synthetic mineral fibers]

Abstract

This paper reports on the evaluation of 21 epidemiological studies concerning investigations in the Man-Made Mineral Fibers (MMF) industries. First conditions of exposure were described. Concentrations of respirable fibers at the production and further treatment of MMF in older plants were in average about a few fibers per cm3, today in most cases remarkable below 1 fiber/cm3. In the old factories also there has been an exposure with very fine fibers with a diameter below 1 micron and this is comparable from its amount with the conditions nowadays. About 55000 workers exposed to MMF were investigated, most of them handling glass fibers. Several thousands of this workforce had a duration of exposure of 20 years or more and a latency time of 30 years or more. No case of mesothelioma was found. A most of the identified cases of pneumoconiosis could be attached to a prior or a concomitant exposure to silica if the occupational exposure was carefully examined. At the recent time there is no wellfounded suspicion that pneumoconiosis is caused by the exposure in the MMF-industries. A few authors supposed, that unspecific structural changes of the lung as occuring also in a greater amount in dependency of smoking habits and age are found more frequently among the employees of this industry than among the common population. Neither the workers with such unspecific structural changes of the lung nor the other members of the workforces had prejudices of lung function. At present time a risk due to MMF to get sick with cancer of the bronchopulmonic system, especially with lung cancer can neither be proved nor be excluded. The epidemiological studies carried out until now were not capable to point out a possibly existing risk in such a ordner of magnitude. It is uncertain if it will be feasable to prove such a risk by using more subtilized methods. This depends at one side on the possibility of clearing up and registering the confounding risk factors. On the other side it must be considered, that the exposure with fibrous dusts even in the old MMF-factories was very much lower than the exposure in the asbestos-industry. It is indispensable to take into account the most important confounding risk factors (smoking habits, preexposure and concomitant exposure with dangerous working materials) in further epidemiological investigations.