Evaluation of the pulmonary inhalation toxicity of diborane

本研究旨在阐明二硼烷（B_2H_6, CAS: 19287-45-7）对大鼠的亚急性肺和睾丸毒性。雄性Wister大鼠连续8周暴露于0.11 ppm或0.96 ppm的二硼烷中，每天6小时，每周5天。对照组暴露在过滤过的空气中。进行支气管肺泡灌洗液（BALF）、血液学、生化及组织病理学检查。对附睾进行精子计数和精子形态改变检查，对睾丸进行组织病理学检查。BALF检查显示，暴露于0.96 ppm的大鼠中性粒细胞百分比呈剂量依赖性增加，巨噬细胞百分比下降。暴露于0.96ppm的大鼠BALF中总磷脂和单个磷脂的数量增加。暴露于0.96 ppm时，大鼠体内磷脂酰甘油和鞘磷脂的比例降低，磷脂酰乙醇胺和磷脂酰肌醇的比例升高。暴露于0.96 ppm的大鼠LDH升高，ALP呈剂量依赖性升高。在血清中，暴露于0.11或0.96 ppm的大鼠α _1-抗胰蛋白酶和超氧化物歧化酶（SOD）活性升高。这些变化对暴露于二硼烷的大鼠的肺显示出剂量依赖效应，可能表明即使暴露于0.11 ppm的大鼠也会出现增殖和/或肥大的II型细胞的高能性，而没有组织病理学改变。睾丸检查未见特别发现。二硼烷的TLV-TWA (0.1ppm)（ACGIH 1991）似乎很高，可能不安全，考虑到大鼠肺8周未观察到的效应水平低于0.11 ppm。目前ACGIH（1991）建议的0.1 ppm TLV-TWA的职业暴露限值似乎过于防止二硼烷对可能反复接触二硼烷的工人的影响。有必要仔细管理工作环境，以避免接触二硼烷。

This study aimed to clarify the subacute pulmonary and testicular toxicity of diborane (B_2H_6, CAS : 19287-45-7) in rats. Male Wister rats were exposed for 8 weeks to 0.11 ppm pr 0.96 ppm of diborane for 6 hours/day, 5days/week. The control group wes exposed to filtered air. Bronchoalveolar lavage fluid (BALF), hematological, biochemical and histopathological examinations were conducted. Sperm counts and spermatic morphological changes were examined in epididymides, and histopathological examination was carried out in testes. BALF examinations revealed that the percentage of neutrophils increased in a dose-dependent manner and that of macrophages decreased in rats exposed to 0.96 ppm. Quantities of total and individual phospholipids in BALF increased in rats exposed to 0.96ppm. The proportion of phosphatidylglycerol plus sphingomyelin decreased, and phosphatidylethanolamine and phosphatidylinositol increased in rats exposed to 0.96 ppm. LDH increased in rats exposed to 0.96 ppm, and ALP showed a dose-dependent increase. In serum, alpha _1-antitrypsin and superoxide dismutase (SOD) activities increased in rats exposed to 0.11 or 0.96 ppm. These changes showed dose-dependent effects on the lung in rats exposed to diborane, possbly indicating that the hyperenergia of type II cells with proliferation and/or hypertrophy without histopathological changes occurred even in rats exposed to 0.11 ppm. Testicular examinations revealed no particular findings. The TLV-TWA of diborane (0.1ppm)(ACGIH 1991) seems to be high and possibly unsafe, considering that the no-observed-effect level over 8 weeks for rat lung was under 0.11 ppm. The current occupational exposure limit of 0.1 ppm TLV-TWA recommended by ACGIH (1991) seems to be too prevent the effects of diborane on workers who may be repeatedly exposed to diborane. It is necessary to manage the working environment carefully in order to avoid exposure to diborane.