Welding involves joining materials, typically metals, by applying high heat to melt and fuse them. However, this activity exposes workers to various substances and energy forms. The International Agency for Research on Cancer (IARC) has classified all welding fumes as carcinogenic to humans, placing them in Group 1, and similarly classified ultraviolet (UV) radiation from welding as carcinogenic.
Carcinogenic Elements in Welding
Welding fumes form when metals are heated above their boiling point, causing their vapors to condense into fine solid particles. These fumes are a complex mixture, primarily composed of metallic oxides, silicates, and fluorides, originating from the electrode, base metal, and coatings. Specific hazardous metallic components can include hexavalent chromium, nickel, cadmium, arsenic, beryllium, manganese, and iron.
Hexavalent chromium, often generated when welding stainless steel or chrome-coated metals, is a highly toxic form of chromium known to damage DNA and cause cancer. Nickel, found in stainless steel and high-alloy materials, is also a recognized carcinogen. Cadmium, present in some stainless steel or plated materials, is causally linked to lung cancer and potentially kidney and bladder cancer. Additionally, the welding arc itself produces intense ultraviolet (UV) radiation. Gases like ozone, nitrogen oxides, and carbon monoxide can also be produced, along with phosgene and hydrogen chloride from the interaction of UV light with chlorinated solvents or thermal breakdown of coatings.
Cancers Linked to Welding Exposure
Exposure to welding fumes and radiation has been epidemiologically linked to several types of cancer. Lung cancer is the most recognized and established risk among welders. Studies indicate an increased risk of lung cancer in welders, with some meta-analyses showing a significant association regardless of smoking status or asbestos exposure.
Beyond lung cancer, welders also face an elevated risk of mesothelioma, a rare cancer often associated with asbestos exposure, which can occur in welding environments. Kidney cancer and bladder cancer have also been observed at increased rates in welders, suggesting a link to specific welding-related exposures. Ocular melanoma, a cancer of the eye, is directly linked to the UV radiation emitted during electric arc welding. Some research has also explored potential links to other cancers, such as those of the stomach or brain, though evidence for these is less conclusive.
Factors Influencing Cancer Risk
Cancer risk for welders varies based on several factors. The duration and intensity of exposure to welding fumes and UV radiation are key. Longer exposure times and higher concentrations of airborne contaminants increase risk. The specific type of welding process used affects the quantity and composition of fumes and gases generated. For instance, processes like Manual Metal Arc (MMA) and Flux-Cored Arc Welding (FCAW) often produce higher fume levels.
The materials being welded, including the base metal, filler material, and any surface coatings or contaminants, directly influence the type of hazardous substances released. Welding stainless steel, for example, can generate hexavalent chromium and nickel. The effectiveness of ventilation in the workspace is critical, as poor ventilation allows fumes and gases to accumulate. Finally, the consistent and correct use of personal protective equipment (PPE) reduces a welder’s exposure to carcinogens.
Protecting Against Welding-Related Cancer
Minimizing exposure to carcinogenic agents during welding requires implementing robust control measures. Proper ventilation systems are essential, including local exhaust ventilation (LEV) to capture fumes at the source and general ventilation to dilute airborne contaminants. These engineering controls are crucial, as no safe exposure level to welding fumes is known.
Personal protective equipment (PPE) forms another important layer of defense. Welders should use appropriate respirators to protect against inhaling fine particulate matter. Welding helmets with suitable filters are necessary to shield the eyes and face from intense UV radiation. Additionally, protective clothing helps prevent skin exposure to UV radiation and hazardous particles. Good hygiene practices, such as washing hands before eating and avoiding eating or drinking in welding areas, reduce ingestion risk. Regular health monitoring for welders can detect early health issues.