Decreased hearing levels at frequencies for understanding speech in tannery workers exposed to a high level of trivalent chromium in Bangladesh
Decreased hearing levels at frequencies for understanding speech in tannery workers exposed to a high level of trivalent chromium in Bangladesh
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DOI：
10.1016/j.chemosphere.2022.135571
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发表时间：
2022-07-09
期刊：
影响因子：
8.8
通讯作者：
Kato，Masashi
中科院分区：
文献类型：
--
作者：
Gu，Yishuo;Ohgami，Nobutaka;Kato，Masashi
据报道，六价铬[Cr(VI)]具有很强的腐蚀性，会导致鼓膜穿孔。三价铬[Cr(III)]也有较弱的腐蚀作用。然而，目前还没有关于接触铬对动物或人类听力水平影响的研究，无论是铬(VI)还是铬(III)。在这项研究中，铬(III)暴露对听力水平的影响是在一项人体研究中确定的。然后，在动物研究中对人类研究结果的重复性和病因学进行了调查。100名孟加拉制革工人的头发和脚趾甲中总铬的平均含量分别是49名非制革工人(办公室工人)头发和脚趾甲中总铬含量的20倍和360倍。多变量分析显示，制革厂工人在1赫兹和4赫兹时听力水平(DHL)下降，这两个频率对理解语言至关重要，但在8赫兹和12赫兹时听力水平下降不明显。由于制革厂工人直接接触的废水中99.99%的t-Cr是铬(III)，流行病学结果表明制革厂工人中存在铬(III)介导的DHLS。本研究的动物实验结果进一步表明，用滴耳液治疗，而不是用与制革工人接触的等量铬(III)腹腔注射，可导致DHL小鼠鼓膜受损。以前的研究表明，铬(III)可以通过空气中的水滴直接到达制革工人的耳膜。铬(III)也可以通过用手指拾取被包括铬(III)在内的制革废水污染的耳道到达鼓膜。总而言之，人类和动物的研究结果表明，通过耳道外部暴露于铬(III)而导致鼓膜损伤，可能会导致DHL。
Hexavalent chromium [Cr(VI)], which has a strong corrosive effect, has been reported to cause perforation of the eardrum. Trivalent chromium [Cr(III)] also has a weak corrosive effect. However, there has been no study on the effects of exposure to Cr, either Cr(VI) or Cr(III), on hearing levels in animals or humans. In this study, the effect of Cr(III) exposure on hearing levels was determined in a human study. Then the reproducibility of the results obtained in the human study and the etiology were investigated in an animal study. The mean levels of total chromium (t-Cr) in hair and toenails from 100 Bangladeshi tannery workers were >20-fold and >360-fold higher, respectively, than those in hair and toenails from 49 Bangladeshi non-tannery workers (office workers). Multivariate analysis revealed decreases of hearing levels (DHLs) at 1 k and 4 k Hz, frequencies that are crucial for understanding language, but not at 8 k and 12 k Hz, in the tannery workers. Since >99.99% of t-Cr in the wastewater that the workers were in direct contact with in the tanneries was Cr(III), the epidemiological results suggest Cr(III)-mediated DHLs in the tannery workers. The results of animal experiments in this study further showed that treatment with eardrops but not intraperitoneal injection with the same amount of Cr(III) that tannery workers might be exposed to resulted in DHL with a damaged eardrum in mice. Previous studies suggested that Cr(III) can directly reach the eardrums of tannery workers via droplets in the air. Cr(III) could also reach the eardrum via picking an ear canal with a finger contaminated with tannery wastewater including Cr(III). Taken together, the results of both human and animal studies suggest the risk of DHLs caused by damage of the eardrum through external exposure to Cr(III) via the ear canal.