重磅 世界衛生組織認定電焊肯定致癌！

筆者剛剛從世界衛生組織WHO屬下的國際癌症研究機構IARC官網上獲悉，前幾天（7月底）頒布的致癌物清單中，有4種化學物質或工藝被確定為肯定致癌物（即1類致癌物）。其中有一種肯定致癌因子為大家經常見到的電焊！下面是該組織的歸類理由。

In March 2017, 17 scientists from ten countries met at the International Agency for Research on Cancer (IARC; Lyon, France) to evaluate the carcinogenicity of welding. These assessments will be published in volume 118 of the IARC Monographs.

2017年3月，來自10個國家的17名科學家在國際癌症研究機構（IARC，法國里昂）開會，評估電焊的致癌性。這些評估將發表在今年的IARC專著第118卷。

Worldwide, an estimated 11 million workers have a job title of welder,and around 110 million additional workers probably incur welding-related exposures. Welding can involve exposures to fumes, gases,radiation (ultraviolet [UV] radiation and electromagnetic fields) and co-exposures to asbestos and solvents.Welding involves several processes (eg, oxyfuel [gas], arc, and resistance welding) and materials (eg, mild and stainless steel). Exposure determinants include the process,material welded, ventilation, degree of enclosure, and use of personal protection.

在世界範圍內，估計有1100萬名電焊工，約1億1000萬名工人可能間接接觸。焊接可以涉及煙霧、氣體、輻射（紫外線（UV）輻射和電磁場）、石棉和溶劑等多種因素的混合接觸。焊接包含幾個工藝（如氧焊（氣體）、電弧和電阻焊接）和材料（例如，低碳鋼和不鏽鋼）。接觸程度取決於工藝、焊接材料、通風、封閉程度和個人防護。

The carcinogenicity of welding fumes was assessed by IARC in 1989 and classified as "possibly carcinogenic to humans" (Group 2B),based on 『limited evidence in human beings』 and 『inadequate evidence』 in experimental animals. UV radiation was classified in Group 1 in volume 100D of the IARC Monographs.Substantial new evidence has since accumulated from observational and experimental studies. In the present evaluation, welding fumes and UV radiation from welding were classified as 「carcinogenic to humans」(Group 1).

在1989，IARC評估了焊接煙霧的致癌性，並將其歸類為「可能對人類致癌」（2B組），基於「有限的人類證據」和「證據不足」的實驗動物。紫外輻射在IARC的編號為100D手冊中被歸類為第1組。從觀察和實驗研究中積累了大量的新證據。在當前的評估中，焊接煙霧和UV輻射被歸類為「對人類致癌」（第1組）。

Arc welding generates UV radiation,a risk factor for the rare cancer ocular melanoma. Various ocular disorders (eg, cataracts or keratoconjunctivis) occur in both welders and nearby workers. Sufficient evidence for the carcinogenicity of UV radiation from welding came from eight partly overlapping case-control studies and two census-based cohort studies that reported on ocular melanoma. Most case-control studies showed positive associations, with risks of developing ocular melanoma generally increased by between two-fold and ten-fold.Two of three studies that assessed risk by duration of employment as a welder showed positive trends.These studies also showed increased ocular melanoma risk associated with eye burns-a proxy for UV exposure-and one reported a positive exposure-response association for cumulative occupational exposure to artificial UV radiation, including welding.Risks persisted after adjustment for sun exposure, sun bed use, or both.

弧焊產生的紫外線輻射是罕見的癌症-眼部黑色素瘤的危險因素。各種眼部疾病（如白內障或角膜結膜炎）都發生在焊工及其相鄰工人。基於焊接UV輻射致癌性的充分證據來自8個部分重疊病例對照研究和2個以人口普查為基礎的隊列研究，報告了眼部黑色素瘤。大多數病例對照研究顯示，眼黑色素瘤發展的風險一般在2倍至10倍增加。3項研究中有2項研究結果顯示與焊工工齡呈正相關。這些研究也顯示了增加的眼部黑色素瘤與眼燒傷有關（UV典型損害），有人報告了累積職業暴露人工紫外線輻射（包括焊接）的正相關關係。剔除陽光暴晒、日光浴混雜因素之後，風險仍然存在。

Welding fumes are produced when metals heated above their melting point vaporise and condense to fine particles (mostly

當金屬被加熱到高於其熔點時，會產生蒸汽並凝結成細顆粒（主要是小於1μm），形成焊接煙霧。大多數研究，包括20多個病例對照研究和近30個職業或基於人群的隊列研究，報告了電焊工或其相鄰工人接觸焊接煙霧，其肺癌風險增加。其他幾個研究也顯示了更加緊密的接觸-反應關係，其中一些研究規模比較大質量還是比較高的。接觸量的評估信息來源於焊接工藝或材料、工業門類、工種、專家評估或自我報告。

Asbestos exposure and tobacco smoking, which are important potential confounders, could not explain the observed excess lung cancer risk in welders. Positive associations persisted after adjusting directly or indirectly for smoking,asbestos co-exposure, or both; restricting to non-smokers or low-level smokers; and in cohorts with low or minimal asbestos exposure.

石棉接觸和吸煙，這是重要的潛在混雜因素，無法解釋觀察到的焊工肺癌患者增加的風險。在考慮這兩個混雜因素之後，依然存在正相關。研究局限於不吸煙者或少量吸煙者；以及在低或最小石棉接觸的人群。

Positive associations for occupation as a welder and kidney cancer were reported in nearly all relevant cohort and case-control studies. However, few studies adjusted for solvents used for cleaning metal in tandem with welding,such as trichloroethylene (a risk factor for kidney cancer). Increased risks were consistently reported across countries,occupational settings, and study designs. However, chance, bias, and confounding could not be reasonably ruled out because some findings were not statistically significant,several studies had few exposed cases,and there was little evidence of an exposure-response association.

幾乎所有相關隊列和病例對照研究表明，電焊和腎癌呈正相關。然而，幾乎沒考慮焊接溶劑如三氯乙烯（腎癌的危險因素）這個混雜因素的影響。儘管如此，不同的國家、專業機構和實驗設計的研究報告結果都一致。然而，偶然性、偏差和混雜不能被合理排除，因為一些發現沒有統計學意義，一些研究只有很少的接觸個案，接觸反應關係證據缺乏。

For all other cancers, the evidence for carcinogenicity was inadequate because of inconsistent findings across studies, insufficient numbers of studies, or the potential for confounding or selection bias. The Working Group concluded that there is 『sufficient evidence in humans』 that welding fumes cause lung cancer and limited evidence for kidney cancer.There is limited evidence in experimental animals for the carcinogenicity of gas metal arc-stainless steel welding fumes. In one oropharyngeal aspiration study and one inhalation study in male A/J mice, gas metal arc-stainless steel welding fumes promoted 3-methylcholanthrene-induced lung tumours.

對於所有其他癌症，致癌性的證據是不夠的，因為多個研究的結果並不一致，研究數量不足，存在潛在的混淆或選擇偏倚。工作組得出結論，焊接煙霧導致人類肺癌證據充足，但導致腎癌證據有限。實驗動物對氣體金屬電弧不鏽鋼焊接煙霧的致癌性的證據有限。1個雄性A/J小鼠經口抽煙和1個吸煙研究，此類焊接煙霧促進3-甲基膽蒽誘導的肺部腫瘤。

Absorption and excretion of metals (chromium, nickel, and manganese) was shown in people exposed to welding fumes, but data for particle deposition and clearance in welders were scarce. Strong evidence suggests that welding fumes induce chronic inflammation and are immunosuppressive. Lung and systemic inflammation biomarkers were increased in many panel studies(of cross-sectional and cohort design)of various arc welding fumes.Risk for infection (pneumonia) was increased in epidemiological studies of different designs. In rodents, welding fumes induced chronic pulmonary inflammation and, in fewer studies,impaired resolution of pulmonary infection.

電焊煙霧接觸者可觀測到金屬（鉻、鎳和錳）的吸收和排泄，但是缺少電焊工顆粒沉積和清除的數據。強有力的證據表明，焊接煙霧引起慢性炎症和免疫抑制。有許多不同弧焊煙霧研究（橫截面和隊列設計）顯示，肺和全身炎症生物標誌物增加。不同設計的流行病學研究顯示，感染（肺炎）風險增加。在嚙齒類動物中，焊接煙霧引起慢性肺部炎症，只在較少的研究肺部感染減輕。

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