Keane Michael, Stone Samuel, Chen Bean, Slaven James, Schwegler-Berry Diane, Antonini James
National Institute for Occupational Safety and Health, Health Effects Laboratory Division, 1095 Willowdale Rd, Morgantown, WV 26505, USA.
J Environ Monit. 2009 Feb;11(2):418-24. doi: 10.1039/b814063d. Epub 2008 Dec 18.
Occupational exposure to welding fumes is a known health hazard. To isolate elements in stainless steel welding fumes with high potential for adverse health outcomes, fumes were generated using a robotic gas metal arc system, using four shield gases of varying oxygen content. The objective was to measure Cr(VI) concentrations in a broad spectrum of gas metal arc welding processes, and identify processes of exceptionally high or low Cr(VI) content. The gases used were 95% Ar/5% O(2), 98% Ar/2% O(2), 95% Ar/5%CO(2), and 75% He/25% Ar. The welder was operated in axial spray mode (Ar/O(2), Ar/CO(2)), short-circuit (SC) mode (Ar/CO(2) low voltage and He/Ar), and pulsed axial-spray mode (98% Ar/2% O(2)). Results indicate large differences in Cr(VI) in the fumes, with Ar/O(2) (Pulsed)>Ar/O(2)>Ar/CO(2)>Ar/CO(2) (SC)>He/Ar; values were 3000+/-300, 2800+/-85, 2600+/-120, 1400+/-190, and 320+/-290 ppm respectively (means +/- standard errors for 2 runs and 3 replicates per run). Respective rates of Cr(VI) generation were 1.5, 3.2, 4.4, 1.3, and 0.46 microg/min; generation rates were also calculated in terms of microg Cr(VI) per metre of wire used. The generation rates of Cr(VI) increased with increasing O(3) concentrations. Particle size measurements indicated similar distributions, but somewhat higher >0.6 microm fractions for the short-circuit mode samples. Fumes were also sampled into 2 selected size ranges, a microspatter fraction (>or=0.6 microm) and a fine (<0.6 microm) fraction; analysis indicated that Cr(VI) is primarily associated with particles <0.6 microm. The conclusion of the study is that Cr(VI) concentrations vary significantly with welding type and shield gas type, and this presents an opportunity to tailor welding practices to lessen Cr(VI) exposures in workplaces by selecting low Cr(VI)-generating processes. Short-circuit processes generated less Cr(VI) than axial-spray methods, and inert gas shielding gave lower Cr(VI) content than shielding with active gases. A short circuit He/Ar shielded process and a pulsed axial spray Ar/O(2) process were both identified as having substantially lower Cr(VI) generation rates per unit of wire used relative to the other processes studied.
职业接触焊接烟尘是一种已知的健康危害。为了分离出不锈钢焊接烟尘中对健康有潜在不利影响的高风险元素，使用机器人气体保护金属电弧系统，采用四种不同氧含量的保护气体来产生烟尘。目的是测量各种气体保护金属电弧焊工艺中的六价铬（Cr(VI)）浓度，并识别Cr(VI)含量异常高或低的工艺。所使用的气体分别为95%氩气/5%氧气（O₂）、98%氩气/2%氧气（O₂）、95%氩气/5%二氧化碳（CO₂）和75%氦气/25%氩气。焊机以轴向喷射模式（氩气/氧气（Ar/O₂）、氩气/二氧化碳（Ar/CO₂））、短路（SC）模式（氩气/二氧化碳（Ar/CO₂）低电压和氦气/氩气（He/Ar））以及脉冲轴向喷射模式（98%氩气/2%氧气（O₂））运行。结果表明，烟尘中的Cr(VI)存在很大差异，即氩气/氧气（脉冲）（Ar/O₂ (Pulsed)）>氩气/氧气（Ar/O₂）>氩气/二氧化碳（Ar/CO₂）>氩气/二氧化碳（短路）（Ar/CO₂ (SC)）>氦气/氩气（He/Ar）；其含量分别为3000±300、2800±85、2600±120、1400±190和320±290 ppm（均值±两次运行的标准误差，每次运行3次重复）。各自的Cr(VI)生成速率分别为1.5、3.2、4.4、1.3和0.46微克/分钟；Cr(VI)生成速率也以每使用一米焊丝产生的微克Cr(VI)来计算。Cr(VI)的生成速率随臭氧（O₃）浓度的增加而增加。粒度测量表明分布相似，但短路模式样品中大于0.6微米的部分略高。烟尘也被采集到两个选定的粒径范围内，一个是微飞溅部分（≥0.6微米）和一个细颗粒部分（<0.6微米）；分析表明Cr(VI)主要与<0.6微米的颗粒相关。该研究的结论是，Cr(VI)浓度随焊接类型和保护气体类型的不同而有显著差异，这为通过选择低Cr(VI)生成工艺来调整焊接操作以减少工作场所的Cr(VI)暴露提供了机会。短路工艺产生的Cr(VI)比轴向喷射方法少，惰性气体保护产生的Cr(VI)含量比活性气体保护低。相对于所研究的其他工艺，短路氦气/氩气保护工艺和脉冲轴向喷射氩气/氧气工艺均被确定为每单位使用焊丝的Cr(VI)生成速率显著更低。
