Studies on Cytotoxic Effects of Brown Coal Dusts

The dusts desposited in the two coal mining places (mine A and mine B) were collected and ground into <5 μm particles in over 95% of constituents by an agae mortar for experiments studies. The standard quartz dusts were offered by the Chinese Academy of Preventive Medicine. The amounts of Zn, Ni, Ca and Al etc. in brown coal dust samples (Dust A, Dust B) were measured by means of x-ray fluorescene and atomic absorption. The silica content was measured by weight method with diphosphoric acid. Alveolar macrophages of wistar male rats were collected and diluted into 2*10 cells/ml. After purification for 1 h, culture medium containing dusts (at a final concentration of 500 μg/ml) was added and cultured for 16 h in 37°C. The rate of survival of cells was determined by counting. The activities of lactic dehydrogenase (LDH) and acid phosphatase (ACP) in the mediums were measured. 120 wistar male rats (weight range: 180–200 g, ages: 60–90 days) were randomly put into four groups. There were 30 in each group. 1 ml of a solution of suspended dusts (50 mg/ml) was injected into the lungs of rats in the quartz or the brown coal groups through the trachea. 1 ml solution of 0.9%NaCl was injected into the lungs of rats in the control group. The rats were killed after 4 months, 8 months and 12 months, respectively. The indexes of the lungs of the rats for wet weight, dry weight, volume and collagen protein content were determined. Changes in the pathological morphology of the rat lung were observed and scored according to Belt and King’s classificatory standard (degree “I”: cellular silicotic nodule, degree “II”: fibro cellular silicotic nodule, degree “III”: cellular-fibrous silicotic nodule, degree “IV”: fibrous silicotic nodule, degree “V”: glass silicotic nodule). All data were processed by analysis of variance.