Data from 90-day quantitative inhalation toxicology study evaluating the dose-response and fate in the lung and pleura of chrysotile-containing brake dust

The final results from this multi-dose, 90-day inhalation toxicology study in the rat with life-time post-exposure observation have shown a significant fundamental difference in pathological response and tumorgenicity between brake dust generated from brake pads manufactured with chrysotile or from chrysotile alone in comparison to the amphiboles, crocidolite and amosite asbestos. The groups exposed to brake dust showed no significant pathological or tumorigenic response in the respiratory track compared to the air control group at exposure concentrations and deposited doses well above those at which humans have been exposed. Slight alveolar/interstitial macrophage accumulation of particles was noted. Wagner grades were 1–2 (1 = control group), similar to the TiO2 particle control group. Chrysotile was not biopersistent, exhibiting in the lung a deterioration of its matrix which results in breakage into particles and short fibers which can be cleared by alveolar macrophages and which...本项针对大鼠的多剂量90天吸入毒理学研究（配套暴露后终生观察周期）所得最终结果显示：与角闪石类石棉——青石棉（crocidolite）与铁石棉（amosite）——相比，以温石棉（chrysotile）制备的刹车片或纯温石棉所产生的制动粉尘，在病理反应与致瘤性方面存在显著的根本性差异。 在暴露浓度与沉积剂量均远高于人类实际暴露水平的条件下，接触制动粉尘的各组大鼠呼吸道未出现显著的病理或致瘤反应，仅观察到轻微的肺泡/间质巨噬细胞颗粒蓄积现象。瓦格纳分级（Wagner grades）为1~2级（1级为对照组），与二氧化钛（TiO₂）颗粒对照组相近。温石棉不具备生物持久性，其在肺内会发生基质降解，断裂为可被肺泡巨噬细胞清除的颗粒与短纤维，且……