Exposure Assessment for Toxicologically Important Chemicals - Welding Fume

这些研究的目的是确定可能的候选行业，工会和工作场所的职业暴露于焊接烟雾（WF），特别强调锰（MN），并招募他们参与暴露评估研究。NIOSH已经确定了评估WF的神经精神影响的具体需求，因为注意到焊接烟雾中锰（Mn）可能导致暴露工人的神经毒性。这项研究将测量焊工的工作场所暴露，特别是那些暴露于明显的锰水平，往往与低碳钢和不锈钢焊接操作。WF中的锰与许多其他金属元素络合，主要是铁、氧化物和氟化物，并且可以以几种价态存在。正在进行文献综述和初步实地调查，以收集必要信息，更全面地制定研究设计和暴露监测策略。地点的选择将取决于：工业部门;焊接工艺;生产率;焊工和其他接触工人的人数;以前的接触记录;预期的接触水平（最好有一系列接触）;以及工作场所条件。NIOSH签订了一份合同，协助招募研究地点和收集工业卫生现场数据。目前正在评估选择可能的候选公司的背景资料，并将招募合适的公司参加这项研究。选择将取决于：工业部门;焊接工艺;生产率;接触的焊工和其他工人的人数;以前的接触记录;预期的接触水平（最好有一系列接触）;以及工作场所条件。六家公司同意与NIOSH合作。文献综述相关的制定原理和设计的工业卫生监测策略和支持分析方法的发展。目前的方法不能区分WF中具有不同价态和溶解度的特定Mn化合物，这些因素可能影响生物利用度和由此产生的健康效应。分析化学探索性研究是在实验室开始的，以调查几种替代分析方法的可行性。评价了连续萃取程序使用不同锰化合物区分不同价态和溶解度的能力。还进行了X射线衍射（XRD）分析，其能够区分不同的价态。焊接烟雾场样品进行了分析，使用扫描和透射电子显微镜（S/TEM）。明场和Z-对比成像被确定为获得尽可能多的信息的关键。此外，使用能量色散X射线分析（EDXA）沿着X射线成像获得元素信息。这些组合技术显示出表征焊接烟雾中锰的形态的承诺，因此空气采样调查应用这些方法进行。该项目的一个重要目标是确定这些分析技术是否可应用于在污染物质量负荷可能较低的工人呼吸区收集的样品。NIOSH的一个电子新闻网站征求与私营部门的合作伙伴关系，允许NIOSH进入他们的焊接活动发生的地点，以评估焊接烟雾的暴露，重点是锰。几家公司表现出兴趣。2009年9月和2010财年，启动了联系，并在5家机构进行了现场访视。这些走查调查的目的是收集支持信息，向工厂和工会代表介绍项目，并收集一系列筛选样本，以帮助开发分析方法。此外，还对颗粒尺寸分布进行了研究。迄今为止，共进行了4次抽样调查，收集了超过90个全轮班工人暴露日。计划再进行六次监测调查。

The purpose of these studies is to identify possible candidate industries, labor unions and workplaces with occupational exposures to welding fumes (WF) with special emphasis on manganese (MN) and recruit their participation in an exposure assessment study. NIOSH has identified a specific need for assessing the neuropsychiatric effects of WF, as concern was noted for the potential of manganese (Mn) in welding fume to cause neurotoxicity in exposed workers. This study will measure workplace exposures of welders, especially those exposed to appreciable levels of Mn, often associated with mild-steel and stainless steel welding operations. Manganese in WF complexes with many other metal elements, chiefly iron, oxides, and fluoride and may exist in several valence states. A literature review and initial field surveys are ongoing to assemble the information necessary to more thoroughly develop the study design and exposure monitoring strategy. Selection of sites will depend on the: industrial sector; welding process(es); production rates; number of welders and other workers exposed; previous exposure records; anticipated exposure levels (preferably with a range of exposures); and work place conditions. NIOSH established a contract for assistance recruiting study sites and industrial hygiene field data collection. Background information for selection of possible candidate companies is being evaluated and suitable companies will be recruited to participate in the study. Selection will depend on the: industrial sector; welding process(es); production rates; number of welders and other workers exposed; previous exposure records; anticipated exposure levels (preferably with a range of exposures); and work place conditions. Six companies agreed to partner with NIOSH. Literature was reviewed relevant to formulate the rationale and design of industrial hygiene monitoring strategies and supporting analytical method development. Current methods do not distinguish between the specific Mn compounds within WF which have different valence states and solubility, factors which could affect bioavailability and resultant health effects. Analytical chemistry exploratory research was initiated in the laboratory to investigate the viability of several alternative analytical approaches. A sequential extraction procedure was evaluated for it's ability to differentiate different valence states and solubilities using different Mn compounds. X-ray defraction (XRD) analysis was also performed which was able to distinguish between different valence states. Welding fume field samples were analyzed using scanning and transmission electron microscopy (S/TEM). Bright field and Z-contrast imaging were determined to be crucial in obtaining the most information possible. Furthermore, elemental information was obtaining using energy dispersive x-ray analysis (EDXA) along with x-ray mapping. These combined techniques show promise for characterizing the welding fumes in regards to Mn speciation; thus air sampling surveys were conducted applying these methods. An important objective of this project will be to determine if these analytical techniques can be applied to samples collected in workers' breathing zones where contaminant mass loading may be low. A NIOSH e-news internet site solicited partnerships with the private sector to allow NIOSH access to their sites where welding activities occur to evaluate exposures to welding fume with emphasis on Mn. Several companies showed interest. Contact was initiated and site visits were conducted at 5 facilities in September 09 and FY10. The purpose of these walk through surveys was to collect supporting information, introduce the project to plant and union representatives, and collect a series of ¿screening¿ samples to aid in the analytical method development. Furthermore, research on particle size distributions was conducted. To date, a total of 4 sampling surveys have been conducted and over 90 full-shift worker days of exposure have been collected. Six additional monitoring surveys are scheduled.