formation leads to membrane damage and therefore disruption of cellular integrity Ref.(9). Due to
the decay of radicals on the fracture surface of quartz, the potential of the quartz particle to cause
fibrosis, is reduced Ref.(10). Presence of aluminum and iron on the mineral lattice of the
crystalline structure of “aged” quartz renders the particle also to be less fibrotic Ref.(11,12). The
yield of OH radicals decrease by more than half if the silica particles are stored in air for 4 four
days Ref.(13). Particle size also play an important role in terms of toxicity. Large particles with a
size of > 0.5µm – 2µm is of importance in the development of silicosis Ref.(14). Earlier reports did
however indicate those particles with sizes less than 1 (one) µm are the most pathogenic Ref.(15).
The geographical area may also play a role in the fibrogenic properties of the crystalline
silica. Hnizdo and Sluis-Cremer Ref.(2) commented that quartz in the South African mines may be
more toxic than Canadian quartz. They stated that this may have serious implications as
international threshold limit values (TLVʼs) or occupational exposure limits (OELʼs) might be too
high and therefore not safe to be used in the South African gold mines.
Pathology associated with crystalline silica exposure
Silica quartz crystals in lung tissue can be observed under polarised light microscopy. Figure 3
illustrates a slide under polarised light microscopy of lung tissue containing crystalline silica
quartz. The white spots represent silica crystals in the specimen of lung tissue. The silica crystals
present in the lung tissue are of different size and represent therefore a typical picture of silica
crystal distribution in lung tissue of a worker exposed to crystalline silica.