Welding Fume Exposures and Controls: Do We Know Enough?
It is safe to assume that we never know enough, or at least don't know all that we need to know. Recent changes to hexavalent chromium and beryllium protection requirements should teach us this lesson.
Welding in the workplace can present significant health hazards unless the potential (and actual) exposures to welding fumes are properly identified, evaluated, and controlled. The sheer numbers of the types of exposure, both acute and chronic, justify a thorough review of the possibilities, the hazards of exposure, and potential controls. This article, while not covering all of these possibilities, may at least prompt environmental, health, and safety professionals to consider these exposures, evaluate actual exposures, and implement appropriate protective measures.
What are Welding Fumes?
Welding is the method typically used to join two or more metal parts through the utilization of heat. The heat causes the metals (or some other material) to melt and, after cooling, to create a strong connection between the metal parts. Welding fumes are essentially a mixture of (somewhat complex but often predictable) metallic oxides, fluorides, and silicates. While this is true, other contaminants and coatings can present an even more complex mixture from which people need to be protected.
It should be noted that:
- The welding process may involve the metals themselves.
- The welding process may also involve the use of a third agent, or "filler" or "flux."
- Welding may occur on new clean stock metal, new metal with residual compounds from manufacture, and/or used or existing metal with residual contamination from operations, including coatings.
Are All Fumes Generated by Welding Operations the Same?
The answer to this is no, unfortunately. While generalizations can be made for mild steel, stainless steel, and various nickel alloys, the truth is that the answer is not so simple. The potential for exposure could include such fumes as: aluminum, beryllium, cadmium, chromium (including hexavalent chrome), copper, fluorides, iron oxides, lead, manganese, nickel, vanadium, and zinc oxides. In addition, the potential for exposure to both source gases and resulting gases from the welding process are possible. We will take a look at all of these in the next section.
Types of Welding
There are many types of welding; the one to be used depends upon the metal substrates, the application, and a variety of other variables. Some of the most commonly used welding methods include:
- Oxy-Acetylene is one of the oldest welding processes, though in recent years it has become less popular in industrial applications. However, it is still widely used for welding pipes and tubes, as well as repair work. It is also frequently well suited, and favored, for fabricating some types of metal-based artwork.
- Arc Welding is popular due to low costs. An electric current is created between the welding device and the materials to be welded, creating an "arc."
- Electroslag Welding is a fast welding process used to join large materials, such as thick steel plates.
- Flux- Cored Welding is an alternative to "stick welding." Flux-cored is used often in automatic, fast-speed applications. Used most often in construction environments.
- Gas Metal Arc Welding is another automatic welding process. The application utilizes a welding gun that automatically feeds the weld metal through the gun for use. The gun also distributes a shield gas for protection from the natural elements. Used widely in automobile repair and manufacturing.
- Gas Tungsten-Arc Welding is the most difficult and time consuming welding process because there is a very small area of space between the arc and the metals being welded. It does, however, create very strong welds (bicycles and aircraft).
- MIG (Metal Inert Gas) Welding is a welding process that uses a gas shield to weld metal. The gas keeps the metal being welded from being affected by natural elements such as oxygen. This method allows for more continuous operation. Note: MIG welding only can be done indoors.)
- Plasma Arc Welding is similar to Gas Tungsten-Arc Welding. The primary difference is in the type of torch used. Plasma arc welding also utilizes a smaller arc and therefore obtains greater precision in a weld. Like GTAW, this is most commonly used in the aircraft industry.
- Shielded Metal Arc Welding is also known as "stick welding." This is the most popular and widely used process today. It is a manual process that is simple and inexpensive. Very often used in construction.
- TIG (Tungsten Inert Gas) Welding is very similar to MIG Welding. The main difference is that TIG uses a tungsten current form while MIG uses a metal electrode. TIG, therefore, requires a filler since the tungsten does not melt. It is used predominantly on stainless steel.
Issues of Concern
As discussed above, there are several contributors to employee exposure to welding fumes during welding operations. The various contributors include:
- the metals being welded on;
- the fluxes, welding rods, and fillers used;
- shielding gases in use;
- coatings and contaminants that may exist on the metal parts; and
- the myriad of gases generated during the welding operation.
Let's take at look at the fumes generated by the various contributors and the potential health effects.
Table I: Health Effects of Fumes, Gases and Organic Vapors During Welding
Fume/Source/Effects and Symptoms
Aluminum/Aluminum component of some alloys, e.g., Inconels, copper, zinc, steel, magnesium brass and filler materials/Respiratory irritant.
Beryllium/Hardening agent found in copper, magnesium aluminum alloys and electrical contacts./"Metal fume fever." A carcinogen. Other chronic effects include damage to the respiratory tract.
Cadmium oxides/Stainless steel containing cadmium or plate material, zinc alloy./Irritation of respiratory system, sore and dry throat, chest pain and breathing difficulty. Chronic effects include kidney damage and emphysema. Suspected carcinogen.
Chromium/Most stainless steel and high alloy materials, welding rods./Increased risk of lung cancer. Some individuals may develop skin irritation. Some forms are carcinogens (hexavalent chromium).
Copper/Alloys such as Monel, brass, bronze. Also some welding rods./Acute effects include irritation of the eyes, nose and throat, nausea and "metal fume fever."
Fluorides/Common electrode coating and flux material for both low and high alloy steels./Acute effect is irritation of the eyes, nose and throat. Long-term exposures may result in bone and joint problems. Chronic effects also include excess fluid in the lungs.
Iron oxide/The major contaminant in all iron or steel welding processes./Siderosis -- a benign form of lung disease caused by particles deposited in the lungs. Acute symptoms include irritation of the nose and lungs. Tends to clear up when exposure stops.
Lead/Solder, brass and bronze alloys, primer/coating on steels./Chronic effects to nervous system, kidneys, digestive system and mental capacity. Can cause lead poisoning.
Manganese/Most welding processes, especially high-tensile steels./"Metal fume fever." Chronic effects may include central nervous system problems.
Molybdenum/Steel alloys, iron, stainless steel, nickel alloys./Acute effects are eye, nose and throat irritation, and shortness of breath.
Nickel/Stainless steel, Iconel, Monel, Hastelloy and other high-alloy materials, welding rods and plated steel./Acute effect is irritation of the eyes, nose and throat. Increased cancer risk has been noted in occupations other than welding. Also associated with dermatitis and lung problems.
Vanadium/Some steel alloys, iron stainless steel, nickel alloys./Acute effect is irritation of the eyes, skin and respiratory tract. Chronic effects include bronchitis, retinitis, fluid in the lungs and pneumonia.
Zinc oxides/Galvanized and painted metal./"Metal fume fever"
Gases/Source/Effects and Symptoms
Carbon monoxide/Formed in the arc./Absorbed readily into the bloodstream, causing headaches, dizziness or muscular weakness. High concentrations may result in unconsciousness or death.
Hydrogen fluoride/Decomposition of rod coatings./Irritating to the eyes and respiratory tract. Overexposure can cause lung, kidney, bone and liver damage. Chronic exposure can result in chronic irritation of the nose, throat and bronchi.
Nitrogen oxide/Formed in the arc./Eye, nose and throat irritation in low concentrations. Abnormal fluid in the lung and other serious effects at higher concentrations. Chronic effects include lung problems such as emphysema.
Oxygen deficiency/Welding in confined spaces, and air displacement by shielding gas. Dizziness, mental confusion, asphyxiation and death.
Ozone/Formed in the welding arc, especially during plasma-arc, MIG and TIG processes./Acute effects include fluid in the lungs and hemorrhaging. Very low concentrations (e.g., one part per million) cause headaches and dryness of the eyes. Chronic effects include significant changes in lung function.
Organic Vapors/Source/Effects and Symptoms
Aldehydes (such as formaldehyde)/Metal coating with binders and pigments, degreasing solvents./Irritant to eyes and respiratory tract.
Di-isocyanates/Metal with polyurethane paint./Eye, nose and throat irritation. High possibility of sensitization, producing asthmatic or other allergic symptoms, even at very low exposures.
Phosgene/Metal with residual degreasing solvents. (Phosgene is formed by reaction of the solvent and welding radiation.)/Severe irritant to eyes, nose and respiratory system. Symptoms may be delayed.
Phosphine/Metal coated with rust inhibitors. (Phosphine is formed by reaction of the rust inhibitor with welding radiation)./Irritant to eyes and respiratory system, can damage kidneys and other organs.
As you can see, there are a wide variety of fumes, gases, and organic vapors to be considered when determining exposures during welding operations.
Although this article is focused on welding fumes and related exposures, be certain to keep in mind some of the other hazards related to welding:
- Eye damage from arc flash
- Thermal burns
- Radiation burns
- Electrical hazards
Several options exist to protect welders from exposure to welding fumes. These include, in accordance with the hierarchy of controls:
- Ventilation, which may include general ventilation and/or local ventilation (Engineering Controls)
- Training and restricted work times/locations (Administrative Controls)
- Respiratory protection, either air-purifying or supplied air (PPE)
Only you can decide which is most appropriate for your workplace and the exposure profiles expected.
Do We Know Enough?
It is safe to assume that we never know enough, or at least don't know all that we need to know. Fairly recent changes to both hexavalent chromium and beryllium protection requirements should teach us this lesson. In addition, recent research has shown a connection between welding fumes and Parkinson's disease (or induced Parkinsonism) possibly as a result of exposure to manganese). Our best option is try to eliminate, or at least minimize, all exposures to these compounds, even well below any established occupational exposure limits.
This article has attempted to review what welding is, what the various welding processes are (and some of their applications), the potential hazardous contaminants of exposure, the source of those contaminants, and the effects and symptoms of the exposures. There are huge resources available to EHS professionals responsible for providing protection for welding applications. Check those resources for the types of welding in your work environment, as well as the metals involved.
This article originally appeared in the September 2012 issue of Occupational Health & Safety.
Robert E. Brown Jr., CIH, CSP, is Director of EHS for G&G Risk Management Consultants, Inc. (www.ggrmc.com) in Antioch, Calif. He has more than 20 years' experience in developing and implementing creative and effective compliance solutions.