Millions of workers in the US and worldwide are exposed to complex, metal-rich welding fumes. Although welding is a crucial industrial process, the generated fumes are known to cause acute and chronic health effects when inhaled. The International Agency for Research on Cancer (IARC) classified welding fumes as carcinogenic to humans (Group 1) in 2017, based on sufficient epidemiological evidence and limited evidence in animals, an upgrade from the former Group 2B (possibly carcinogenic to humans) classification. There is human evidence that both iron-abundant mild steel as well as chromium- and nickel-containing stainless steel welding fumes contribute to an increased risk of lung cancer. Recent animal studies show that welding fumes may act as lung tumor promoters, regardless of the presence or absence of potentially carcinogenic metals, such as chromium and nickel. The goal of this manuscript was to examine the pulmonary responses associated with welding fumes by reviewing a series of recent experimental animal studies that assessed the influence of welding fume metal composition (e.g., stainless steel versus mild steel welding fume) on markers of lung toxicity and tumor development. Additional in vivo laboratory studies are needed to further explore the association between welding and lung cancer and to help advance our understanding of a potential mechanistic link.
Keywords: A/J mice; chromium; iron; lung cancer; welding.