Authors: S.J Milne, C.J. Pretorius, J.I Phillips, And J. Murray

Source: Silica And Associated Respirable Mineral Particles, STP 1565, Martin Harper And Taekhee Lee, Eds., Pp. 180-196, ASTM International, West Conshohocken, PA, 2013


Abstract: There is an association between exposure to silica dust and the development of silicosis. Studies have shown that the weight of silica dust retained in the lung is related to the presence and severity of silicosis. To study the dust retained in the lung a method of isolating it is required. Some studies suggest that lung tissue digestion methods, using acids, alkalis, or heat, alter the composition of silica dust retained in the lung. This study aimed to investigate whether methods used to digest lung tissue and isolate the retained dust are suitable for midsagittal sections of lung from deceased South African gold miners with silicosis. Ten methods were identified to digest lung tissue in the literature. Seven of these methods were carried out on midsagittal lung sections from cases with either moderate or marked silicosis. Of these, four methods digested a substantial portion of the lung tissue. Digestion using 30 % H2O2 with the addition of chloroform lipid extraction yielded the most complete lung tissue digestion. The composition of standard silica (NIST 1878a) was not altered using 30 % H2O2 and chloroform, but minor changes to the background silver filter were noted using X-ray powder diffractometry (XRD). The use of 11.3N HCl, 25 % NaOH, and 40 % KOH altered the composition of NIST 1878a. The composition of three NIST 1878a samples, placed in a muffle furnace at 380C for 2 h was also compared to untreated NIST 1878a, and found to be unaltered. A method to rapidly digest a midsagittal section of lung has been developed. It has been shown that isolating dust using this method does not alter its composition.

Keywords: pneumoconiosis, silicosis, NIST 1878, lung, midsagittal section