Liu Sa, Hammond S Katharine, Rappaport Stephen M
Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA 94720-7356, USA.
Ann Occup Hyg. 2011 Apr;55(3):305-18. doi: 10.1093/annhyg/meq088. Epub 2011 Feb 25.
BACKGROUND/AIMS: Exposures to total particulate matter (TP) and manganese (Mn) received by workers during welding and allied hot processes were analyzed to assess the sources and magnitudes of variability.
Compilation of data from several countries identified 2065 TP and 697 Mn measurements for analysis. Linear mixed models were used to determine fixed effects due to different countries, industries and trades, process characteristics, and the sampling regimen, and to estimate components of variance within workers (both intraday and interday), between workers (within worksites), and across worksites.
The fixed effects explained 55 and 49% of variation in TP and Mn exposures, respectively. The country, industry/trade, type of ventilation, and type of work/welding process were the major factors affecting exposures to both agents. Measurements in the USA were generally higher than those in other countries. Exposure to TP was 67% higher in enclosed spaces and 43% lower with local exhaust ventilation (LEV), was higher among boilermakers and was higher when either a mild-steel base metal or a flux cored consumable was used. Exposure to Mn was 750% higher in enclosed spaces and 67% lower when LEV was present. Air concentrations of Mn were significantly affected by the welding consumables but not by the base metal. Resistance welding produced significantly lower TP and Mn exposures compared to other welding processes. Interestingly, exposures to TP had not changed over the 40 years of observation, while those of Mn showed (non-significant) reductions of 3.6% year(-1). After controlling for fixed effects, variance components between worksites and between-individual workers within a worksite were reduced by 89 and 57% for TP and 75 and 63% for Mn, respectively. The within-worker variation (sum of intraday and interday variance components) of Mn exposure was three times higher than that of TP exposure. The estimated probabilities of exceeding occupational exposure limits were very high (generally much >10%) for both agents.
Welding exposures to TP and Mn vary considerably across the world and across occupational groups. Exposures to both contaminants have been and continue to be unacceptably high in most sectors of industry. Because exposures to the two agents have different sources and characteristics, separate control strategies should be considered to reduce welders' exposures to TP and Mn.
背景/目的：分析焊接及相关热加工过程中工人接触的总颗粒物（TP）和锰（Mn），以评估其来源和变化程度。
汇总来自多个国家的数据，确定了2065次TP测量值和697次Mn测量值用于分析。采用线性混合模型确定不同国家、行业和工种、工艺特征以及采样方案所产生的固定效应，并估计工人内部（日内和日间）、工人之间（工作场所内）以及不同工作场所之间的方差成分。
固定效应分别解释了TP和Mn暴露变化的55%和49%。国家、行业/工种、通风类型以及工作/焊接工艺类型是影响两种污染物暴露的主要因素。美国的测量值通常高于其他国家。在封闭空间中TP暴露高出67%，采用局部排气通风（LEV）时低43%，在锅炉制造工人中暴露较高，使用低碳钢母材或药芯焊丝时暴露也较高。在封闭空间中Mn暴露高出750%，有LEV时低67%。Mn的空气浓度受焊接耗材显著影响，但不受母材影响。与其他焊接工艺相比，电阻焊产生的TP和Mn暴露显著更低。有趣的是，在40年的观察期内TP暴露没有变化，而Mn暴露显示出（不显著的）每年3.6%的下降。在控制固定效应后，不同工作场所之间以及工作场所内个体工人之间的方差成分，TP分别降低了89%和57%，Mn分别降低了75%和63%。Mn暴露的工人内部变化（日内和日间方差成分之和）比TP暴露高三倍。两种污染物超过职业暴露限值的估计概率都非常高（通常远大于10%）。
全球范围内以及不同职业群体中，焊接过程中TP和Mn的暴露差异很大。在大多数工业部门，两种污染物的暴露一直且仍然高得令人无法接受。由于两种污染物的暴露来源和特征不同，应考虑采用不同的控制策略来减少焊工对TP和Mn的暴露。
