Exposure to Welding Fumes and Gases

It’s critical workers are protected against dangers of welding.

By Jerome E. Spear

Welding produces various contaminants at a sufficient rate to cause both short- and long-term health effects if not properly controlled. A comprehensive review of epidemiological studies of welders indicates a large number of welders experience some type of respiratory illness—bronchitis, airway irritation, lung function changes, and a possible increase in the incidence of lung cancer.

More than 500,000 workers are employed in welding and related occupations in the United States according to the Bureau of Labor Statistics. Another 200,000 welders or more are retired. That adds up to a potential pool of more than 700,000 people who have been exposed to welding fumes.

Pulmonary infections may also increase in terms of severity, duration, and frequency among welders following their exposure to welding. Studies have also associated chronic exposure to manganese with a risk for Parkinson’s disease.

The first step is to understand the potential health effects and recognize the factors affecting a welder’s potential exposure to welding fumes and gases.

The best way for a company to reduce the potential of large settlements is to provide documented evidence the company is progressively making efforts in controlling exposure to welding fumes and gases.

The first step is to understand the potential health effects and recognize the factors affecting a welder’s potential exposure to welding fumes and gases.

Health Effects

Welding fumes are small particles that are formed when the vaporized metal rapidly condenses in the air. Typically too small to be seen by the naked eye, the particles collectively form a visible plume.

The health effects associated with metal fumes depend on the specific metals present in the fumes. These effects may range from short-term illnesses such as metal fume fever (with flulike symptoms) to long-term lung damage or neurological disorders such as lung cancer and Parkinson’s disease.

Gases are also generated from welding, which may include carbon monoxide, ozone, and nitrogen oxides.

Carbon monoxide is an odorless, colorless gas that may be formed by the incomplete combustion of the electrode covering or flux and by the use of carbon dioxide as a shielding gas. Overexposure to carbon monoxide hinders the body’s red blood cells from carrying sufficient oxygen to other tissues within the body, which subsequently results in asphyxiation.

Welding does not normally generate carbon monoxide at high enough levels to be a concern. However, high levels of carbon monoxide may potentially accumulate when welding or air arc gouging in confined spaces. Also, there’s the potential of an oxygen-deficient atmosphere if welding inside a confined or enclosed space if an inert gas (such as argon) is used as the shielding gas.

Ozone, nitrogen dioxide, and nitric oxide are produced by the interaction of ultraviolet light from the welding arc with the surrounding air. These compounds are irritating to the eyes, nose, and throat.

High exposures can also cause fluid in the lungs and other long-term pulmonary illnesses. If the metal has been degreased with a chlorinated solvent, other airborne gases (phosgene, hydrogen chloride, chlorine gas) may be produced. These gases generally cause irritation to the eyes, nose, and respiratory system—and symptoms may be delayed.

Common Welding Processes

The type of welding process is directly related to the amount of fumes and gases generated. And so, it is important to have a basic understanding of the welding process in order to assess the risk of exposure.

Shielded metal arc welding (SMAW)

Also called stick welding, and commonly used for carbon steel welding and low alloy welding. In SMAW, the electrode is held manually, and the electric arc flows between the electrode and the base metal. The electrode is covered with a flux material, which provides a shielding gas for the weld to help minimize impurities. The electrode is consumed in the process, and the filler metal contributes to the weld. SMAW can produce high levels of metal fumes and fluoride exposure; however, stick welding is considered to have little potential for generating ozone, nitric oxide, and nitrogen dioxide.

Gas metal arc welding (GMAW)

Sometimes referred to as metal inert gas (MIG) welding, typically used for most types of metal and is faster than shielded metal arc welding. This process involves the flow of an electric arc between the base metal and a continuously spool-fed consumable electrode. Shielding gas is supplied externally; hence, the electrode typically has no flux coating or core. Although GMAW requires a higher electrical current than shielded metal arc welding, GMAW produces fewer fumes since the electrode has no fluxing agents. However, due to the intense current levels, GMAW produces significant levels of ozone and nitrogen oxides.

Flux-cored arc welding (FCAW)

Used for carbon steels, low alloy steels, and stainless steels. This welding process has similarities to both shielded metal and gas metal arc welding. The consumable electrode is continuously fed from a spool and an electric arc flows between the electrode and base metal. The electrode wire has a central core containing fluxing agents and additional shielding gas may be supplied externally. This welding process generates a substantial amount of fumes due to the high electrical currents and the flux-cored electrode. However, FCAW generates little ozone, nitric oxide, and nitrogen dioxide.

Gas tungsten arc welding (GTAW)

Also known as tungsten inert gas (TIG) welding, is used on metals such as aluminum, magnesium, carbon steel, stainless steel, brass, silver, and copper-nickel alloys. This technique uses a non-consumable tungsten electrode. The filler metal is fed manually and the shielding gas is supplied externally. High electrical currents are used, which causes GTAW to produce significant levels of ozone, nitric oxide, and nitrogen dioxide.

Submerged arc welding (SAW)

Another common welding process used to weld thick plates of carbon steel and low alloy steels. In this welding process, the electric arc flows between the base metal and a consumable wire electrode. The arc, though, is not visible since it is submerged under flux material. This flux material keeps the fumes down and since the arc is not visible, there is little ozone, nitric oxide, and nitrogen dioxide generated. The major airborne hazard with SAW is the fluoride compounds generated from the flux material.

Fume Generation Rates

The primary source of information when determining the components likely to be in the fumes is the safety data sheet (SDS) of the consumable welding electrode/wire. About 90% to 95% of the fumes are generated from the filler metal and flux coating/core of consumable electrodes. Since the base metal weld pool is much cooler than the electrode tip, the base metal contributes only a minor amount of the total fumes. However, the base metal may be a significant factor of the fume exposure if the metal or surface residue contains a highly toxic substance (lead, cadmium).

Also, the American Welding Society has conducted and published studies that provide the concentrations of selected metal constituents in the fumes produced by various welding electrodes. In addition to the welding technique, studies have shown the fume generation rate is also influenced by the following factors.

  • Electrical current: In general, the fume generation rate is exponentially proportional to the current.
  • Arc voltage: The fume generation rate generally increases when the arc voltage increases.
  • Electrode diameter: The electrode diameter has a modest effect on the fume generation rate because of the differences in voltage and current. In general, a small diameter electrode generates more fumes than a large diameter electrode.
  • Electrode angle: The angle of the electrode to the work piece has a slight (but unpredictable) effect on the fume generation rate.
  • Shielding gas: In gas-shielded arc welding, the fume generation rate tends to be greater when carbon dioxide (as opposed to argon) is used as the shielding gas.
  • Speed of welding: As the welding rate increases, the fume generation rate obviously increases.
  • Steady/current pulsed current welding: Technology has advanced to power sources that have pulsing capabilities. Recent studies have shown that using a pulsing current during welding generates fewer fumes than under a steady current welding process.

In general, flux-cored arc welding produces the greatest fume generation rate (for mild steel welding) followed by shielded metal, gas metal, and gas tungsten arc welding.

Since most of the fumes are attributed to the welding consumables, there has been a drive to develop a number of “low-fume” consumables. The focus appears to be in the reformulation of the flux-cored wire to low-carbon strip materials for the tube and less mineral compounds for the core.

This information should be considered when performing an initial exposure assessment. The welding process and composition of the material (primarily the ingredients in the electrode unless the steel is coated) should be the basis of categorizing similar exposure groups.

High alloy materials tend to contain metals with lower occupational exposure limits (such as chromium, nickel, copper). The similar exposure groups can be further defined by the specific task, the position of the work piece (in relation to the welder’s breathing zone), the presence or absence of local exhaust ventilation, and other work-related factors.

Jerome E. Spear, CSP, CIH, is president of J.E. Spear Consulting and has more than 22 years of experience helping organizations prevent injuries and illnesses, control losses, and achieve regulatory compliance. He held the positions of technical services manager with XL Specialty Risk Consulting and corporate industrial hygiene manager for Chicago Bridge and Iron Co., a worldwide steel fabricator and construction company.