Young T, Myers J E, Thompson Mary Lou
Department of Public Health and Family Medicine, University of Cape Town, South Africa.
Neurotoxicology. 2005 Dec;26(6):993-1000. doi: 10.1016/j.neuro.2005.05.002. Epub 2005 Jun 21.
A major recent review of occupational exposure limits for manganese (Mn) has proposed a respirable dust level of 0.1 mg/m3. There is, however, no theoretical basis for using this exposure metric to estimate the systemic effects of Mn, and little in the way of empirical data relating respirable Mn to neurobehavioural and other non-pulmonary effects. Cross-sectional data from a study showing few and unconvincing neurobehavioural effects of inhalable dust in Mn smelter workers published just prior to this review were reanalyzed here using respirable Mn. The hypotheses tested were that respirable Mn exposure is a more appropriate predictor of neurobehavioural effects than inhalable Mn where such effects exist, and that there should be no observed effects at respirable dust levels below 0.1 mg/m3.
Five hundred and nine production workers and 67 external referents were studied. Exposure measures from personal sampling included the Mn content of respirable dust as a concentration-time integrated cumulative exposure index (CEI) and as average intensity (INT) over a working lifetime. Neurobehavioural endpoints included items from the Swedish nervous system questionnaire (Q16), World Health Organisation neurobehavioural core test battery (WHO NCTB), Swedish performance evaluation system (SPES), Luria-Nebraska (LN), and Danish Product Development (DPD) test batteries, and a brief clinical examination.
The median respirable Mn exposure was 0.058 mg/m3 (range=0-0.51; IQR=0.02-0.16) amongst the exposed, with 30% having average intensities above the proposed 0.1 mg/m3 and 44% above the proposed supplemental limit of 0.5 mg/m3 inhalable dust. As in the study of inhalable Mn effects, there were few respirable Mn effects showing clear continuity of response with increasing exposure.
These data did not provide empirical support for a respirable, as opposed to an inhalable, dust metric being more sensitive in the identification of Mn effects. Neither metric showed convincing effects within the exposure range studied. Further study is needed to determine a threshold for respirable Mn effects, if such exist, and to verify our findings.
最近一项关于锰（Mn）职业接触限值的主要综述提出可吸入粉尘水平为0.1毫克/立方米。然而，使用该接触指标来估计锰的全身效应没有理论依据，而且关于可吸入锰与神经行为及其他非肺部效应的经验数据也很少。在本次综述之前刚刚发表的一项研究的横断面数据显示，锰冶炼工人中可吸入粉尘对神经行为的影响很少且不令人信服，本文使用可吸入锰对这些数据进行了重新分析。所检验的假设是，在存在此类效应的情况下，可吸入锰暴露比可吸入锰更适合作为神经行为效应的预测指标，并且在可吸入粉尘水平低于0.1毫克/立方米时不应观察到效应。
对509名生产工人和67名外部对照者进行了研究。个人采样的接触测量包括可吸入粉尘中的锰含量，作为浓度-时间综合累积接触指数（CEI）以及工作寿命期间的平均强度（INT）。神经行为终点包括瑞典神经系统问卷（Q16）、世界卫生组织神经行为核心测试组（WHO NCTB）、瑞典绩效评估系统（SPES）、鲁利亚-内布拉斯加（LN）和丹麦产品开发（DPD）测试组中的项目，以及简短的临床检查。
暴露组中可吸入锰暴露的中位数为0.058毫克/立方米（范围=0-0.51；四分位间距=0.02-0.16），30%的人平均强度高于提议的0.1毫克/立方米，44%的人高于提议的可吸入粉尘补充限值0.5毫克/立方米。与可吸入锰效应的研究一样，很少有可吸入锰效应显示随着暴露增加反应有明显的连续性。
这些数据没有为可吸入粉尘指标（与可吸入粉尘指标相对）在识别锰效应方面更敏感提供经验支持。在所研究的暴露范围内，这两个指标都没有显示出令人信服的效应。需要进一步研究以确定可吸入锰效应的阈值（如果存在）并验证我们的发现。
