Welding and associated processes such as arc-cutting, are routinely performed by pipefitters, ironworkers, boilermakers and sheet metal workers; other trades may also weld and perform thermal cutting of metals. This work often occurs in tanks or boilers or in other poorly ventilated settings. The fume generated during welding contains fine particles composed of the constituents in the base metal, the electrodes, fluxes, and the filler rods; these particles can deposit in the lungs or enter the blood stream by passing through the lungs. Welding can also create hazardous gases (see Table 1 below). Construction workers can be exposed to the hazards of chromium and manganese; the exposure varies with the welding process and the specific metals used. Estimates of the number of workers exposed to welding fumes range from 410,000 full-time welders to over one million workers who weld intermittently.
The American Welding Society has identified over 80 different types of welding and allied processes in commercial use. Of these processes, some of the more common types include shielded manual metal arc welding, gas metal arc welding, flux-cored arc welding, gas tungsten arc welding, and others such as submerged arc welding, plasma arc welding, and oxygas welding.
The chemical properties of welding fumes can be quite complex. Most welding materials are alloy mixtures of metals characterized by different steels that may contain iron, manganese, silica, chromium, nickel, and others. Fumes are released from the base metal and from welding rods, and gases are produced from some of the arc welding processes; see table 1.
Table 1. Hazardous Byproducts of Welding
FUME |
GASES |
RADIANT ENERGY |
OTHER HAZARDS |
Aluminum |
Carbon Dioxide |
Ultraviolet |
Heat |
Cadmium |
Carbon Monoxide |
Visible |
Noise |
Chromium III & VI |
Nitrogen Oxide |
Infrared |
Vibration |
Copper |
Nitrogen Dioxide |
|
|
Fluorides |
Ozone |
|
|
Iron |
|
|
|
Lead |
|
|
|
Manganese |
|
|
|
Magnesium |
|
|
|
Molybdenum |
|
|
|
Nickel |
|
|
|
Silica |
|
|
|
Titanium |
|
|
|
Zinc |
|
|
|
There are a number of health effects caused by exposure to welding fume, including:
-
metal fume fever
-
COPD/bronchitis and asthma
-
lung cancer
-
neurological injury from manganese, like Parkinson’s disease
Metal fume fever: This is a frequent acute respiratory complaint among welders. Symptoms include flu-like symptoms like cough, shortness of breath and fever, lasting a few hours. It is caused by exposure to welding fumes that contain zinc, copper, magnesium, and cadmium.
COPD/Bronchitis: Chronic obstructive pulmonary disease (COPD) includes chronic bronchitis and emphysema. Chronic bronchitis is present when someone has a regular cough with phlegm for at least 3 months over two successive years, and there is no medical condition causing the cough. Emphysema is present when there is destruction of the walls of the airspaces of the lung. The destruction of airspaces means there is less lung surface; loss of lung surface reduced the ability of the lung to transfer oxygen into the body and transfer waste gases out.
Individuals with COPD often are in their 50s, with 20 or more years of smoking and/or occupational dust and fume exposure. A cough with phlegm starts so slowly as to be barely noticeable, first occurring only in the morning. Then someone with COPD gets frequent chest illnesses with cough, sputum, and wheezing. As the COPD gets worse, the intervals between these chest infections grow shorter. In severe COPD, loss of oxygen delivery occurs, and over time this decrease in oxygen can lead to heart failure.
Smoking is the primary cause of COPD, but smoking alone does not explain all COPD, as only 15-20% of smokers developed COPD and 10% of deaths from COPD occur in persons who never smoked. Occupational exposures to dusts and chemicals (vapors, irritants, fumes) increase the risk of developing COPD; the specific exposures associated with COPD in construction are wood dusts, cadmium, silica, welding fumes, cement dust, and possibly isocyanates.
One study, “A case-control study of airways obstruction among construction workers”, examined occupational exposures to vapors, gases, dusts and fumes (VGDF) among older construction workers between 1997 and 2013, comparing 834 workers with COPD and 1,243 controls. Approximately 18% (95% CI=2-24%) of COPD in this population can be attributed to workplace exposures associated with construction tasks. After adjusting for smoking habits in this population, the study also revealed among construction workers who never smoked, 32% (95% CI=6-42%) of COPD was attributable to the workplace.
Lung cancer: Welders have an increased risk for lung cancer, but it is not clear whether that is due to the welding emissions or to asbestos exposure which was common in construction decades ago. The International Agency for Research on Cancer has concluded that welding fumes may cause cancer, and welders of stainless steel have higher rates of lung cancer. Metal fume exposure from stainless steel welding is of particular concern because it contain chromium and nickel, both of which are known to cause cancer in workers. Recent studies show among the stainless steel welders, the risk of lung cancer increased significantly with increasing accumulative welding particulate exposure, It is still unresolved whether the mild steel welding process carries a carcinogenic risk.
Parkinson-like disease: Manganese is a component of nearly all steels and is present in many welding rods and wires. Manganese has been known to cause neurological injury for many years. The first cases were reported in 1837. A paper in 1955 on manganese poisoning among miners described “manganese madness” with mood swings followed by the development of tremor, abnormal gait, and other symptoms akin to Parkinsonism.
Parkinson’s disease occurs at a rate of 200 cases per 100,000 persons. About 2% of the population over age 65 has Parkinson’s disease. Symptoms include tremor at rest, slowing and loss of movement, stiffness, stooped posture and loss of balance. Pathologically these symptoms are due to loss of nerve cells in a specific part of the brain, the basal ganglia. Based on autopsies in humans and experiments in animals, the pattern of brain injury from manganese is somewhat different from that of Parkinsonism, but the symptoms are similar because the injury occurs in the same basic structures, areas that control movement and muscle tone.
It is clear there is a risk from manganese exposure in mining, ore extraction, and work with metals that have high manganese content. There is less information on the risk from the lower levels of Mn during welding exposures, but current research suggests a risk for Parkinson-like disease among welders. One study of Parkinsonism among welders found that the disease among welders was similar to Parkinson’s in other people, except that it occurred at a younger age. More information can be found at the NIOSH website:
http://www.cdc.gov/niosh/topics/welding/.