Welding fume is composed of very fine, solid particles of metal oxides that form during the welding process. The makeup of welding fume is dependent on many factors, including the composition of the material being welded, the welding method and the type of shielding.
The amount of each substance a welder inhales is dependant on several additional variables, including welding amperage, welding position, area ventilation (or weather conditions if outdoors) and local ventilation. Accurate exposure assessment usually requires air sampling by an industrial hygienist or trained individual.
Exposures to certain components of welding fume above the occupational exposure limits negatively can affect many parts of the body, including the lungs, heart, kidneys, reproductive system and central nervous system.
Short-term effects from over-exposure to airborne welding fumes can include irritation of the eyes, nose and throat; coughing; shortness of breath; bronchitis; increased infections of the respiratory tract; fluid in the lungs (pulmonary edema); and a flu-like illness known as metal fume fever.
According to the American Welding Society (AWS) Fact Sheet #25, metal fume fever may be caused by exposure to excessive concentrations of welding fume containing zinc, magnesium, copper and cadmium. The most common cause of metal fume fever is overexposure to fumes generated by welding on galvanized steel. Symptoms usually occur within 4 hours of exposure and can include nausea, chills, fever, thirst, muscle ache, chest soreness, coughing, fatigue and a metallic taste in the mouth. These flu-like symptoms may last 6 to 24 hours, and complete recovery without intervention usually occurs within 24 to 48 hours after exposure, providing there is no additional exposure.
Long-term welders face a 30 to 40 percent increased risk of lung cancer.1 This could be due to the high rate of smoking among welders, frequent exposure to asbestos or exposure to welding fumes. Other potential cancer-causing components of welding fume are hexavalent chromium and nickel.
Manganism is a central-nervous system disease that is linked to manganese exposure. The link between manganism and welding fume containing manganese currently is under investigation.
Siderosis is a buildup of iron nodules in the lung that may have no direct adverse effect but may aggravate other lung illnesses.
The best way to avoid both short- and long-term illnesses related to welding is to control respiratory hazards.
CONTROLLING FUME HAZARDS
Before beginning any welding job, it's critical to identify potential respiratory hazards and their airborne concentrations particular to that operation. Fume exposure will depend on the following factors:
The type of welding. Welding amperage, shielding gases and pulsing within each method significantly can influence fume generation rates.
The materials being welded: base metals, electrodes and surface coatings.
The position of the welder relative to the rising smoke plume.
The ability to remove welding fumes at the point of generation using ventilation.
In many cases, engineering controls alone may not be feasible or may not reduce exposure levels adequately. In such cases, it may be appropriate to use respirators to help reduce exposures to airborne contaminants.
The unit cost of respirators can range from around $1 for a basic negative-pressure, disposable, filtering facepiece respirator to $1,000 or more for a powered or supplied air respirator system. When several different respirators will reduce the exposure to an acceptable level, there are several factors to consider besides the price.
Reusable respirators may last longer, but they require daily cleaning and maintenance — an added labor cost that often is overlooked. Depending on the type of unit, maintenance may include washing, filter changing, battery charging, inspection and component replacement.
Depending on job conditions, disposable filtering facepiece respirators quickly can become clogged or damaged, making the long-term cost of replacement offset the lower cost.
Training requirements and respirator maintenance costs vary. For example, consider if users will be trained to maintain their personal units or if designated maintenance personnel will be responsible for these tasks.
Comfort is even more important than cost. Respirators must be worn the entire time the worker is exposed to hazardous contaminants, so consider the comfort and fit of the respirator and the tasks the worker is performing. Additionally, required use of respirators with tight-fitting facepieces requires fit testing prior to use.
Another safety consideration is heat stress, which may result in reduced productivity, reduced quality, increased risk of accidents and higher turnover. Supplied air respirator systems employing vortex cooling technology may counter heat stress. These lightweight, belt-mounted devices require that breathing-quality air be supplied from a remote compressor through an air hose. Air entering the headpiece can be lowered by up to 50 degrees F. Some systems provide warmed air when cold stress is an issue.
Proper use of respiratory protection requires a written respiratory protection program, per OSHA 29 CFR 1910.134, including medical clearance, training and fit testing. Work with your respirator manufacturer to help identify the best solution for your workers' exposures.
- James M. Antonini, “Health Effects of Welding.” Critical Reviews in Toxicology. Vol. 33, No. 1 (2003), pp. 61-103.
Derek Baker is a mechanical engineer and technical service specialist for 3M Co., Occupational Health and Environmental Safety Division.