Document EvaN40w6XYVBOonggpE1ZQm1V

Industrial Hygiene Digest Februarr, 19S6 INDUSTRIAL DUSTS 240 Silicosis Rlak in Relation to Silica Doit la the Environment and to Length of Exposure tq a Ceramic* Factory. F. M. Troisi an<i N. Zurio. Mad. lavoro 4S. 614-423 (Nov." iS5-4J. Italian with Engliak tamnury. The author* conducted a aurvey of a glased tile factory, including airborne duet counts and determinations of free silica in the raw materials and settled and airborne dusts. Both the clay and ingredients of the glaze contributed to the dust The atmospheric concen tration of quartz under 5 microns In diameter varied from 196 particles per cc. to below 30, depending upon location. Three cases of early silicosis were found among 22 selected em ployeos who had worked at the same tasks for over 20 years, although annual x-ray examin ations had shown no cases of silicosis. Control measures are discussed. -- Cond. from Bull. Kyg. 241 Statistical Synthesis of the Chemtcal-Petrofixaphlc Determinations of Free Silica in Some Argillaceous Materials. E. Occella. Med, lavoro 45, 715-720 (Dec. 19541. Italian with English summary. The author reports on the examination of about 600 samples of clay and clay-like materials used In industry. The data are graphically charted and tabulated according to tree crystalline silica content. The samples representing materials used in brldaaaklag are also charted separately. Only quartz particles under S microns seed to be considered when dealing with the silicosis hazard, and the brick-making clays are classified according to the content of the fine quartz particles. Practically all the samples (excluding kaolins) contained quarts la varying proportions up to S59&, averaging 10%. The silicosis hazard from any one material is directly proportional to the degree of subdivision of the free silica particles, and this degree of subdivision may be inversely proportional to the total free sil ica content. However, - the considerations applying to the raw material may not necessarily hold for the atmosphere of the place of work, where, on the one hand, baking of the ware may increase the temper of the material so as to favor further subdivision of the quartz and, on the other hand, the hazard may entirely disappear because the quartz reacts and combines with other oxides which are available at certain temperatures. -- Cond. from BulL Hyg. 242 Particle Size and Petrographic Analysis of Some ArgUlacsouj Materials. E. Occella. lied, lavoro 45, 721-729 (Dec. 1954). Italian with English summaryT* This paper deals with a total of nine mineral samples of raw materials used in the manufacture of earthenware, ceramics, bricks, and tiles. The loose and semi-loose particles ware separated by sifting through screens of 4 to 400 mesh. Smaller particles down to 10 mi crons were analyzed by appropriate mechanical apparatus, and the still Oner constituents, down to 1-micron, were determined by'the polarizing microscope. Durban's technique (QtF Abst. 1146, Dec- 1946) was then used to estimate the free silica content of each sample and of each of its granulometric groups. The'results are tabulated and shown graphically. In general the samples with a lower quartz content were richer la the finer and more dangerous quartz particles. Therefore, in assessing the silicosis hazard from any particular raw mater ial, U is not sufficient to estimate the overall free crystalline silica content without studying the granulometric distribution of particles of less than 5 microns in diameter. -- Cond. from Bull. Hyg. 11 206 1379