Similar patterns of cognitive and motor deficits have been widely reported from manganese exposures in welding, metallurgical and chemical industry workers. A risk assessment was performed based on studies reported in the literature, extending some earlier work, and deriving new estimates of exposure response and excess risk. Many investigations of manganese neurological effects in humans have insufficient information to derive an exposure response; however, findings from a chemical manufacturer, two smelter and two welder populations permitted application of the benchmark dose procedure for continuous end-points. Small particles and aggregates of condensation fume (condensing vaporized metal, <0.1 μm in diameter) appear to have a higher potency per unit mass than larger particles from dusts (>1.0 μm). Consideration was given to long-term effects of continuous low exposures that instead of producing increasing toxicity attain a steady-state condition. Impairment was defined as excursions beyond the 5th percentile in a normal population and the concentrations of manganese predicted to result in 1% excess prevalence of impairment over different time periods were calculated. Over five years, exposures resulting in 1% excess prevalence of impairment (for purposes of discussion) were in the vicinity of 10 μg/m³ for manganese fume and 25 μg/m³ for larger particle dusts. These levels are below current recommendations for occupational limits on manganese exposure in the United States.

从焊接，冶金和化学工业工人的锰暴露中已广泛报道了类似的认知和运动缺陷模式。基于文献报道的研究进行了风险评估，扩展了一些早期的工作，并得出了暴露响应和超额风险的新估计。关于人体锰神经系统作用的许多研究都缺乏足够的信息来得出暴露反应。但是，化学品制造商，两个冶炼厂和两个焊工的调查结果允许对连续终点应用基准剂量程序。冷凝烟雾的小颗粒和聚集体（冷凝的汽化金属，直径<0.1μm）似乎比粉尘中的较大颗粒（> 1.0μm）具有更高的单位质量效价。考虑了连续低暴露的长期影响，而不是产生增加的毒性而达到稳态。减损定义为正常人群中超出5个百分点的偏移，并计算了在不同时间段内导致减损患病率超标1％的锰浓度。五年来，导致损害患病率超标1％的暴露（出于讨论目的）约为10μg/ m³为锰灰和25微克/米³为较大颗粒的粉尘。这些水平低于美国现行有关锰暴露职业限制的建议。