OBJECTIVETo study the pulmonary toxicity to rats induced by different sized SiOz particles.

METHODSOne hundred and five male SD rats were divided into seven groups randomly according to their weight. Experimental rats were exposed to 20, 50, 80, 140, 280 and 800 nm SiO2 particles at the dose of 400 mg/m3 by inhalation for 2 hours respectively. The control group was exposed without SiO2 particles. At the 24th, 48th, 72th hour after exposure, five rats were sacrificed at each time point and the total cellular scores, total protein, lactate dehydrogenase (LDH) in BALF and the histopathological changes in lungs were observed.

RESULTSThe total cellular score, total protein and lactate dehydrogenase in bronchoalveolar lavage fluid (BALF) of all experimental groups were higher than the control group. Between 800 nm group and the control group, there were no significant changes in total cellular sare, total protein and LDH in BALF (P > 0.05). At 48 h, the total cellular score of 280 nm group had no significantly change compared with the control group, but the total protein and LDH in BALF of 280 nm group were significantly higher than the control group (P < 0.05). The total cellular score at 24 h and the total protein at 24, 48 h had no significantly changes compared with the control group, but other indexes of 140 nm group were significantly higher than the control group. All the indexes of the 20, 50, 80 nm group were significantly higher than the control group (P < 0.05), and higher than 800 nm group mostly time. The TCS, total protein and LDH in BALF increased firstly and then reduced. The experimental group visible part pulmonary alveolus gap varying degree proliferation accumulation, its periphery has massive phlogocyte accumulation,such as granular cells and macrophage.

CONCLUSIONUnder this condition ,the SiO2 particles can cause lung damage more serious with the smaller diameter SiO2 particles. As time going on, the damage caused by SiO2 particles is not so serious as before.