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Characterization of welding fumes for welders during welding processing
water-soluble metals,welding fume,respirable particulate matter,chromium VI,oxidic nickel,soluble nickel,cancer risk assessment,
|Publication Year :||2018|
|Abstract:||研究目的:分析電焊燻煙物理化學特性並建立微粒肺部暴露情形，估算暴露濃度，了解空氣暴露與體內暴露劑量關係；以電焊作業人員暴露在電焊燻煙中Cr (VI)、oxidic nickel (Ni) 及soluble Ni濃度估算其癌症風險，並分析能影響暴露濃度之危險因子。
本研究首先用可分離粒徑大小之分階採樣器，進行管線建造電焊作業人員之空氣樣品採集，該電焊作業為戶外作業，混合使用二種電焊方法，分別為SMAW(shielded metal arc welding)及GTAW (gas tungsten arc welding)，將Fe、Al、Zn、Cr、Mn、Cu、Ni及Pb以水萃取為水溶性金屬部分(WS)及不水溶性金屬部分(WI)，並以ICP-MS (inductively coupled plasma- mass spectrometry )進行其中金屬濃度分析。
收集3種電焊作業類別人員共計105人，採集其作業環境空氣樣品進行chromium (Cr) 及 nickel (Ni)濃度分析，再推衍空氣中致癌金屬Cr (VI)、oxidicNi及soluble Ni濃度及其累積劑量，使用美國EPA (Environmental Protection Agency)提出的Incremental Lifetime Cancer Risk (ILCR)模式計算累積暴露所致致癌風險。
質量粒徑分佈圖為雙峰對數常態分佈，大於10 微米粒子佔總質量60.3%，小於10 微米粒子佔總質量39.7%。電焊燻煙中金屬濃度由高而低遞減排序為Fe > Al > Zn > Cr > Mn > Ni > Cu > Pb。粒徑 < 0.52 微米及 > 14.8 微米粒子具有豐富的金屬，然而0.52–14.8 微米粒子則相對含有較少金屬，金屬水溶性(WS)百分比部分，與金屬種類有關，但與金屬粒徑區間無關。水溶性金屬含量比例由高而低遞減依序為Zn、Mn、Pb、Cu、Cr、Al、Fe及Ni。比較金屬溶解在水的能力，Zn、Mn 及 Pb較Cu、Cr、Al、 Fe 及 Ni高。綜合考量粒子大小在肺部各區域沉積百分比、粒徑區間金屬成分及金屬水溶性，推算可達肺泡氣體交換區之水溶性金屬約佔空氣中金屬含量百分比為4.9– 34.6%。
吸入性致癌風險結果顯示三種暴露族群的暴露風險是有差異性，致癌風險由高至低依序遞減為管線建造電焊、壓力容器製造電焊及造船廠電焊，其原因為電焊作業條件並不相同，所以產生不同Cr及Ni暴露濃度的情境。利用Monte Carlo模擬來進行風險機率分佈時，其最敏感的參數為Cr及Ni暴露濃度。與Cr及Ni暴露濃度有相關的解釋變項為使用在不鏽鋼之SMAW (shielded metal arc welding)電極填充物(x1)、使用在不鏽鋼之GTAW (gas tungsten arc welding)電極填充物(x2)及不鏽鋼基材(x3)。
可抵達肺部氣體交換區之可溶性金屬濃度建議取代傳統空氣中金屬濃度，可較準確地評估電焊燻煙之體內暴露劑量。本研究結果顯示電焊作業人員致癌風險屬高風險族群，不鏽鋼電焊填充物及不鏽鋼基材與空氣中Cr (VI)、oxidic Ni 及soluble Ni濃度有相關性。
Objective: the study characterized the physicochemical property of welding fumes and estimate the levels of the water-soluble metals present in inhalable, thoracic, and respirable particulate matter. In addition, the study designed to investigate exposure to Cr (VI), oxidic nickel (Ni) and soluble Ni in welding fume for welders, which are responsible for cancer risk and determine associated risk factors for exposure to carcinogenic metals.
Methods: the study analyzed air samples obtained using size-fractioning cascade impactors that were attached to the welders performing shielded metal and gas tungsten arc welding outdoors. Iron, aluminum, zinc, chromium, manganese, copper, nickel, and lead concentrations in the water-soluble (WS) and water-insoluble (WI) portions were determined separately, using inductively coupled plasma mass spectrometry.
Cancer risks regarding exposure to chromium, hexavalent chromium (Cr (VI)), oxidic nickel (Ni), and soluble nickel in welding fumes. Personal air samples were taken for analysis of Cr and Ni, and the concentrations of Cr (VI), oxidic Ni, and soluble Ni were derived. The study used the Incremental Lifetime Cancer Risk (ILCR) model proposed by the United States Environmental Protection Agency to calculate excess risk.
Results: the log–normal mass–size distribution having two modes exhibited 39.7% of PM having sizes less than 10 micrometer, and 60.3% of PM having sizes greater than 10 micrometer. The metal concentrations in the welding fume were ranked as follows: Fe > Al > Zn > Cr > Mn > Ni > Cu > Pb. In this study, PM having sizes < 0.52 micrometer and > 14.8 micrometer were rich in metals, whereas PM having sizes ranging from 0.52 to 14.8 micrometer contained a relatively low amount of metals. In the WS portion, the capacities of metals dissolving in water are correlated with the metal species but particle sizes. The WS metals varied with the metal species in a decreasing order as follows: Zn, Mn, Pb, Cu, Cr, Al, Fe, and Ni. Particularly, Zn, Mn, and Pb exhibit relatively higher capacities than Cu, Cr, Al, Fe, and Ni. Exposure of the gas-exchange region of the lungs to WS metals were in the range of 4.9% to 34.6% of the corresponding metals in air by considering the particle-size selection in lungs, metal composition by particle size, and the capacities of each metal dissolving in water.
The study ranked the excess cancer risk in decreasing order: pipeline construction, pressure container manufacturing, and shipyard building. Our results imply that cancer risks from exposure to Cr and Ni in welding fumes are comparable in different exposure groups because welding performance affected the formation of fumes. The most sensitive parameters for risk assessment with the Monte Carlo simulation were the concentrations of Cr and Ni. The statistically significant determinants in association with Cr and Ni concentrations were the following: the presence of stainless steel as base metal, filler metals of shielded metal arc welding (SMAW) method, and filler metals of gas tungsten arc welding (GTAW) method used in stainless steel.
Conclusion: exposure of the gas-exchange region of the lungs to WS metals becomes important exposure levels of metals, instead of airborne concentrations, to accurately evaluate the health risk from exposure to welding fume. Furthermore, the study revealed that welders belong to a high-risk group of cancer. Moreover, we demonstrated the roles of filler metals and stainless steel in the exposure to Cr and Ni.
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