Inhalation Toxicity of Man-Made Mineral Fiber (MMMF)

在本实验中，Wistar雄性大鼠42只和雌性Wistar雌性大鼠45只，分别暴露于玻璃纤维(GB-100R，日本研华东洋公司)(含SiO_2 63%)，每天6小时，每周5天，连续4周。在慢性吸入毒性试验中，27只Wistar雄性大鼠也暴露于玻璃纤维1年。Andersen取样器测量的空气动力学质量中值直径为2.7um，扫描电子显微镜测量的计数中值直径和长度分别为0.51um和5.5um。暴露期间，男性组和女性组的日平均暴露浓度分别为10.8+-3.3 mg/m^3和9.8&lt；+-3.0 mg/m^3，男性组为4周，女性组为2.2&lt；+0.6 mg/m^3。纤维颗粒浓度…用光散射法监测曝光室中S的数量，并在暴露期间保持不变，分别于暴露1、2、3、4周后24小时，暴露4周后3.5、5.5、6、12个月清除期后处死大鼠。对于玻璃纤维对肺沉积的慢性影响，他们在暴露1年后立即处死，并在暴露1年后的1年清除期后处死。测量大鼠肺湿重和肺中二氧化硅浓度，用等离子加速器对肺进行低温灰化(约150ﾟC)，灰化后，用碳酸钠在铂锅中熔化，用分光光度法测定硅含量，根据接触玻璃纤维大鼠与对照组的硅含量差值计算大鼠肺中硅的沉积量。暴露4周的雄性大鼠的玻璃纤维沉积量高达300微克，与暴露时间成正比。对于慢性暴露，观察玻璃纤维沉积量，分别在暴露1年后清除1年后观察到1.5 mg和0.6 mg。男性和女性的表观沉积分数分别为4.5%和4.7%。表观沉积分数定义为暴露期间肺部沉积的量与吸入的玻璃纤维量之比。表观沉积分数在雌雄大鼠之间没有显著差异，在清除期间，沉积的硅含量随着清除时间的增加而减少。在单室模型中，雄性和雌性大鼠的生物半衰期被确定为1.5个月；暴露4周，但暴露1年，生物半衰期为9.2个月。生物半衰期随暴露时间的延长而增加。这可能是由于纤维沉积导致清除活性降低所致，但本实验中未发现恶性肿瘤。10.关键词少

Pulmonary deposition and the clearance of deposited particles from lungs are very important factors to induce pneumoconioses and tumors.In this experiment, 42 Wistar male and 45 Wistar female rats were exposed to glass fiber (GB-100R, Advantec Toyo, Co., Japan) (content : SiO_2 63 %) for 6 hrs/day, 5 days/week for 4 weeks, and for chronic inhalation toxicity test, 27 Wistar male rats were also exposed to glass fiber for 1 year. The mass median aerodynamic diameter was 2.7 mum by an Andersen sampler, and the count median diameter and length determined by a scanning electron microscope were 0.51 mum and 5.5 mum, respectively. The daily average exposure concentration was controlled by a continuous fuluidized bed with a screw feeder and an overflow pipe at 10.8 <plus-minus> 3.3 and 9.8 <plus-minus> 3.0 mg/m^3 during the exposure period in the male group and female group for 4-week exposure, respectively and 2.2 <plus-minus> 0.6 mg/m^3 for 1-year exposure. The fibrous particle concentration … More s in the exposure chamber were monitored by a light scattering method and were constant during the exposure.The rats were sacrificed at 24 hours after 1, 2, 3 and 4 weeks exposure and after 3.5, 5.5, 6 and 12 months clearance period following a 4-week exposure. For chronic effect of glass fiber on lung deposition, they were killed just after the 1-year exposure and after 1 year clearance period following a 1-year exposure. The wet lung weight and the silica concentration in thelungs were measured and the lungs were treated for low temperature ashing (ca. 150 ﾟC) by using a plasma asher.After ashing, these samples were melted with sodium carbonate in a platinum pot to measure the silicon content by the absorption spectrophotometry.The amount of deposited silicon in rat lungs by exposure to glass fiber was calculated from the difference value of measured silicon content between the exposed rats and controls. The deposited amount of glass fiber which was observed up to 300 ug in the 4-week exposed male rats, was proportional to the exposure period. For chronic exposure, the deposited amount of glass fiber was observed 1.5 mg and 0.6 mg after the 1-year clearance just after 1-year exposure. The apparent deposition fraction which is defined as the deposited amount in the lungs to the amount of the inhaled glass fiber during the exposure, was 4.5 % and 4.7 % in male and female, respectively. There was no significant difference in the apparent deposition fraction between male and female rats.During the clearance period, the deposited silicon content decreased with the increasing of the clearance period. The biological half time in the one-compartment model was determined to be 1.5 months in male and female rats ; for 4-week exposure, but 9.2 months for 1-year exposure. The biological half time increased with the increasing of the exposure period. The cause of this may be decrease of clearance activity by fiber deposition, however, there were no malignant tumor in this experiment. 10. KEY WORDS Less