Diatomaceous earth quarried from the remains of aquatic plants deposited millions of years ago, continues to be a very important raw material with many industrial uses. In its natural state, diatomaceous earth is an amorphous silica with no
crystalline
pattern. For many uses, however, it is calcined and calcination converts a portion of the amorphous silica to a crystalline form, cristobalite which is far more fibrogenic.
In the factory which calcination was done with diatomaceous earth two workers were proved as pneumoconiosis on August 1990. Therefore, a follow-up study was perfomed on the workers who received periodic medical examination and can be collected 53
chest
radiographs among 24 workers from 1988 to 1992. The radiographs were doubly read by one chest disease specialist and radiologist and their findings were classified by International Classification of Radiographs of Pneumoconiosis (ILO, 1980).
@ES The results were as follows;
@EN 1. The airborne concentrations of total dust during 4 consecutive years were 1.01~7.80mg/㎥ below TLV.
2. The incidence density of diatomaceous earth pneumoconiosis was 6.26 among 100 person-year.
3. Chest radiographs were progressed ever if exposure of diatomaceous earth has been stopped and the degree of progress was different from an individual.
Above results suggest that early detection of diatomaceous earth pneumoconiosis will be important for medical surveillance of workers in the diatomite factory.
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