Welding and cutting operations may present a significant health hazard to workers if metal fumes are not adequately evaluated and controlled. Understanding the nature of metal fume exposure represents an important first step in protecting the health and safety of employees performing welding, cutting and brazing operations.
What are Metal Fumes?
Welding “smoke” generally consists of a complex mixture of very fine particles and gases. The high temperatures caused by welding or torch cutting activities converts existing metals into vapors which then condense into very small particulates referred to as metal fumes.
What are Metal Fumes Composed of?
The composition of metal fumes varies greatly based upon the composition of the base metals, coatings, electrodes and fluxes. Carbon steel consists primarily of iron and carbon but can contain trace amounts of other elements such as manganese. Stainless steel may contain between 10%-30% chromium and often contains nickel (among other trace elements). Stainless steel is of particular concern from occupational safety perspective in that the high temperatures generated during welding or torch cutting activities may convert the chromium to its hexavalent state, resulting in the generation of highly toxic hexavalent chromium fumes. Alloy steels contain very little carbon but often include a wide variety of other metals including manganese, nickel, chromium, molybdenum, tungsten, and vanadium. Other components of steel may include aluminum, antimony, arsenic, beryllium, cadmium, cobalt, lead, tin, zinc and other trace elements.
What Effect do Coatings have on Metal Fume Composition?
While the chemical composition of various types of steel may be relatively consistent, the composition of coatings including primers and paints may greatly impact the overall composition of the metal fumes. Galvanized steel, for instance, is coated with zinc to protect against corrosion. Paints and primers often contain other toxic metals including arsenic, cadmium and lead which can become volatilized during the welding and cutting process. And while the use of lead in paint and primers was banned for residential purposes in 1978, the use of lead in other coatings continued well past this date for many industrial, specialty and other non-residential applications.
What are the Potential Health Effects of Metal Fume Exposure?
Many of the substances in welding fumes are toxic and have been associated with both short-term and long-term health effects. Short-term exposure to metal fumes (including zinc, magnesium, and copper) may cause chills, fever, muscle aches, dizziness, fatigue, and nausea and may result in a condition known as “metal fume fever.” Welding fumes may also irritate the eyes, nose, and respiratory system and can cause coughing, wheezing, bronchitis, pulmonary edema and pneumonitis.
Prolonged exposure to welding fumes may cause damage to the lungs as well as various types of cancer, including lung, larynx and urinary tract cancer. Health effects from certain fumes can include stomach ulcers, gastrointestinal impairment, kidney damage, reproductive system damage and nervous system damage. Prolonged exposure to manganese fumes have been associated with neurological problems and may damage the lungs, liver, kidneys and central nervous system. Hexavalent chromium exposure may cause damage to the eyes, skin, nose, throat and lungs and has the potential to cause cancer. Certain metals such as cadmium, nickel, beryllium, chromium and arsenic are also considered to be suspected or known carcinogens.
How are Welding Fumes Evaluated?
Due to the toxicity of the aforementioned compounds, the Occupational Safety and Health Administration (OSHA), American Conference of Governmental Industrial Hygienists (ACGIH) and other organizations have published various occupational exposure limits for exposure to these compounds. All available information should be considered in determining the primary contaminants of concern present including product documentation, the type of welding or cutting activities performed, sampling results for paints and coatings, and an evaluation of the types of base metals present. The findings of this review can then be used to develop a sampling plan to evaluate the concentrations of contaminants present, as well as the effectiveness of existing work practices and engineering controls. Where existing work practices and engineering controls are not sufficient to limit exposure to within acceptable ranges, a careful evaluation of available personal protective equipment (PPE) should be performed to select the most appropriate PPE given the type of operation and anticipated levels of exposure.
Due to the variety of factors involved with the recognition and evaluation of metal fumes in the work environment, controlling occupational exposure to metal fumes remains a significant challenge. Fortunately, a wide variety of evaluation and control measures are available to protect workers from occupational exposure to the various contaminants of concern.
For more information on how to best protect workers within your work environment, please seek the advice of your qualified occupational safety or industrial hygiene specialist.
For more information on your environmental/industrial hygiene concerns contact Michael Brennan at True North Consultants, Inc.: