The toxicity of welding fumes has been a matter of immense concern amongst welders, before inferring if they are indeed toxic, it will be essential to have a good grasp of their compositions and the mode of generation.
Welding fumes refer to the solid metal suspended in the air which forms when vaporized metal condenses into tiny particulates.
When this vaporized metal comes in contact with oxygen in the air, a reaction occurs, and the vaporized metal becomes oxidized thereby producing metal oxides that condense and form fume consisting of particles that are primarily of respirable size.
The composition and the rate of generation of welding fumes are characteristic of the various welding processes and are affected by the electrode coating, shielding gas, flux, paint or surface coating, welding current, and the skills and techniques of the welder.
The concentration of the fume in the welder’s vicinity is also a function of the volume of the space in the welding environment and the efficiency of fume removal by ventilation.
How Are Welding Fumes Toxic?
Welding fumes are toxic in the sense that exposure to them can cause metal fume fever that can include flu-like symptoms, cough, breathing difficulty, muscle pain, fever, and chills.
Exposure to high levels can result in nose, eye and throat irritation, nausea, or a metallic taste in the mouth.
Long-term exposure to low levels of welding fume may also cause decreased lung function, pneumonia, wheezing, infertility, or cancer. These health effects may vary depending upon the specific metals in the welding fume.
Various metals have a varying intensity of toxicity which of course implies the toxicity of welding fumes varies, some may pose more potential hazards than others, depending on their inherent toxicity.
The most common welding fume components and their dangers as follows.
Exposure to Lead can occur during welding and cutting of any metal coated with lead-based paint or lead.
Lead poisoning is uncommon in welders but may occur in persons employed in operations like shearing lead-painted steel in ship breaking and bridge demolition.
Lead poisoning, which amongst welders results from exposure to oxide fumes of lead, may affect the blood, gastrointestinal tract and nervous system.
Cadmium is an element sometimes used in the manufacture of fluxes for certain flux-cored electrode, or as a coating in certain materials.
Inhalation of Cadmium oxide fume may cause acute irritation of the respiratory passages, bronchitis, chemical inhalation lung injury or excessive fluid in the lung tissues (pulmonary edema).
There may be a dormant period of a few hours between exposure and the onset of symptoms. The effects of prolonged exposure to cadmium fumes may resemble metal fume fever initially, and just a single exposure to a very high concentration of cadmium oxide fume may be lethal, Severe cadmium poisoning results in injury to lungs and kidneys.
Exposure to manganese occurs when using this metal as a flux agent in coatings or an electrode wire or electrode cores as an alloying element.
Critical poisoning from oxides of manganese is very rare in welders, although respiratory tract irritation from its fumes may result. Exposure to fumes from welding on manganese steel can give rise to chronic inflammation of the lungs. Metal fume fever is also a potential after exposure to manganese fume.
Chronic manganese poisoning, characterized by a severe disorder of the nervous system, has been recorded in welders working in confined spaces on steel with high manganese content.
Zinc can be present as a surface coating on steel products which are known as galvanized steel.
A welder may experience a brief severe self-limiting illness known as metal fume fever, zinc chills or brass founders’ ague when exposed to freshly formed zinc oxide.
The symptoms, which resemble those of a severe attack of respiratory tract infection, usually occur about 6-8 hours after the inhalation of the fume and is characterized by flu-like symptoms, a sweet, metallic taste in the mouth, excessive thirst, high fever, and a non-productive cough and usually with complete recovery within about 24 to 48 after exposure.
Leukocytosis, a transient increase in white blood cell counts, is reported to be a common finding in metal fume fever but is known to be less common amongst welders.
Ferrous materials are the most commonly welded materials; the most abundant constituent of ferrous alloy welding fume is iron oxide.
Iron oxide is considered a cloud of nuisance dust with little likelihood of causing chronic lung disease after inhalation. Extended exposure to such a welding fume can lead to the deposition of iron oxide particles in the lungs, which can be seen as fine discrete opacities on chest X-ray films when present in large quantities.
This is present in some steel alloys. Molybdenum fumes may produce bronchial irritation and slight fatty changes in the kidneys and liver.
This is a component in some high-strength, high-temperature alloys. Shortness of breath, coughing, and pneumonitis can occur after inhalation of cobalt fumes. Hypersensitivity appears to be involved because Pulmonary function changes occur at varying intensity and time of onset. In most cases, the symptoms disappear after exposure ends.
This may be present in some metal electrodes and special alloy steels. Exposure to its oxide fume gives rise to severe irritation of the eyes, severe throat and respiratory tract irritation, and may also cause chemical pneumonia.
Nickel is a potentially carcinogenic metal found in fumes from the welding of nickel-plated mild steel, stainless steel, and high-strength low-alloy steel electrodes.
Oxides of Nickel has been found carcinogenic in laboratory animals. Epidemiology studies show a correlation between the exposure of workers in nickel refineries to mixtures of soluble and insoluble nickel compounds and increased incidences of nasal and lung cancers and asthma.
There appear to be substantial differences in the carcinogenic potency of different nickel compounds.
This may be present as a coating on the workpiece, and mainly in stainless steel, hardfacing and chrome-alloy electrodes. Chromium usually is not present in any significant amount in aluminum alloys. Chromate generated in stainless steel welding fumes or fumes from hardfacing and chrome-alloy electrodes is an irritant to the mucosal tissue in the respiratory tract.
Exposure to fume containing high concentrations of water-soluble chromium (VI) during the welding of stainless steel in confined spaces has been reported to result in chronic chrome intoxication, dermatitis, and asthma.
Epidemiological studies and animal tests have confirmed sure chromium (VI) compounds as carcinogenic.
Silica and Silicates
The silica and silicates formed in welding fumes are amorphous, that is, not crystalline, and are
generally believed not to be harmful.
Certain welding processes make welders exposed to fluoride dust, fume, and vapors. Fluoride fumes may produce irritation of the eyes, throat, respiratory tract and skin. Chronic fluorosis is a syndrome characterized by an increased density of bones and ligaments due to fluoride deposition. However, no corroborating data are available which identify a relationship between exposure to fluoride-containing welding fumes and disorders of bones or ligaments.
How to prevent being poisoned
knowing how to handle toxic welding fumes is essential but what could be more important than avoiding them in the first place.
The following are the necessary precautions to observe when trying to prevent welding fumes poisoning.
I recommend thorough local ventilation for controlling welding fume exposures whenever possible. Some portable systems may be helpful at your site when working indoors to reduce exposure to fumes and gases. Such systems include extractor guns and vacuum nozzles, which should be kept as close as possible to fume source.
Also, flexible exhaust systems can be used to draw the fumes away from the welder. Ensure that the exhaust port of these ventilation systems is away from other workers as well.
Stay upwind when welding outdoors. That is, the direction of travel of the welding fumes should be away from the welder.
Welding outdoors and in open environment does not guarantee safe ventilation.
Ensure you have a standby worker close by when welding in confined spaces. If possible, avoid working in such locations.
Don’t take chances; be sure to wear respiratory protection if ventilation cannot reduce fume exposures to safe levels.
Wear respiratory protection if ventilation and work practices don’t adequately reduce welding fume exposure to safe levels.
Wear appropriate gloves, sleeves, encapsulating suits, and other protective clothing to prevent skin contact with welding fumes.
The safest practice when working on coated steel is to remove the coatings before welding altogether to prevent the coatings from becoming toxic vapors when in contact with the heat of the arc. You can achieve this by using an angle grinder and flap wheel.
In some cases, change the product design of toxic. You can replace NiCd rechargeable batteries with NiMH alternative. These contain other toxic metals, such as chromium, vanadium, and cerium. Different metals often replace cadmium. Use zinc or Nickel plating instead of cadmium plating, and brazing filler alloys now rarely contain cadmium
Educate workers regarding the features of the syndrome of exposure to welding fumes and the proactive measure to take when exposed, to make them understand the hazards associated with welding.
What to do if poisoned
If toxic welding fumes overcome a person and gases, the following precautions should be
- Remove the patient to an uncontaminated atmosphere and loosen tight clothing at the neck and waist;
- Keep the patient warm and at rest;
- If the patient has difficulties in breathing, dispense oxygen to him/her, provided that suitable apparatus and a trained operator are available.
- If breathing is subtle or has ceased, artificial respiration should be applied (the mouth-to-mouth or mouth-to-nose methods are preferred); and
- seek medical advice.
- It is crucial for the doctor to know the contaminants which might have been present in the air of