[Incidence of pneumoconiosis and the fibrogenic properties of dust occurring during the production of thermallite bricks].

Notifications of occupational diseases among building ceramics industry workers were analysed. During 1976-1980 six cases of pneumoconiosis among those workers were diagnosed. All those cases referred to workers of two divisions dealing with transport and preparation of raw materials for the production of thermallite brick of a mixture of clay from Jarosław, siliceous earth from Piotrowice and sawdust. Experiments on animals confirmed a very high biological aggressiveness of unheated siliceous earth and weak fibrogenic activity of clay dusts and dusts emitting from the burned thermallite brick. Diffractometric tests of the dusts indicated that the high biological aggressiveness of siliceous earth was due to alpha-crystoballite of low crystallinity. Under effect of high temperature (during brick burning) crystoballite of siliceous earth is subject to great changes (the degree of crystallinity gets increased), which results in its decreased fibrogenic properties. The experiments on animals confirmed a weak biological aggressiveness of the dust from burnt thermallite brick and considerably decreased aggressiveness of siliceous earth heated at 1200 degrees C for 4 hours, as compared to unheated siliceous earth. The weak fibrogenic activity of the dust of clay containing approx. 15% of alpha-quartz may be due to kaolinite and illite in this dust.