Welding fume causes cancer, neurological damage, lung disease, and kidney damage. That’s not speculation. IARC classified all welding fume as a Group 1 carcinogen in 2017. Manganese in mild steel fume causes Parkinson’s-like symptoms that don’t reverse. Hexavalent chromium in stainless steel fume causes lung cancer at exposure levels most unprotected welders exceed. Zinc oxide from galvanized steel causes acute metal fume fever. None of this is new information. The data has been accumulating for decades. What’s new is that it’s getting harder to ignore.
This article covers what’s in the fume, what it does to your body, and which processes and materials create the highest risk. It’s not meant to scare you away from welding. It’s meant to make you take fume extraction and respiratory protection seriously enough to actually use them.
What’s in Welding Fume
Welding fume is a complex mixture of metal oxides, gases, and ultrafine particulates generated when metals are heated above their boiling point during welding. The arc vaporizes base metal and consumable wire or electrode, and these vapors condense in the air as fine particles (primarily 0.01-1.0 microns in diameter).
The composition of the fume depends on what you’re welding and what process you’re using.
Fume Components by Base Metal
| Base Metal | Primary Fume Components | Key Hazard |
|---|---|---|
| Mild steel (A36, 1018, etc.) | Iron oxide, manganese, silicon | Manganese (neurological) |
| Stainless steel (304, 316, etc.) | Hexavalent chromium, nickel, iron oxide, manganese | Hexavalent chromium (carcinogen) |
| Galvanized steel | Zinc oxide, iron oxide | Zinc oxide (metal fume fever) |
| Aluminum | Aluminum oxide | Aluminum (respiratory irritant) |
| Chrome-moly steel | Chromium, molybdenum, manganese | Chromium (carcinogen) |
| Cadmium-plated steel | Cadmium oxide | Cadmium (kidney/lung damage, carcinogen) |
| Lead-painted steel | Lead oxide | Lead (neurological, kidney) |
Fume Generation Rates by Process
Different welding processes generate different volumes of fume. This matters for ventilation sizing and personal exposure levels.
| Process | Fume Generation Rate (g/min) | Relative Fume Volume |
|---|---|---|
| GTAW (TIG) | 0.01-0.05 | Very Low |
| GMAW (MIG, short circuit) | 0.1-0.5 | Low to Moderate |
| GMAW (MIG, spray transfer) | 0.3-1.0 | Moderate to High |
| SMAW (Stick) | 0.5-2.0 | Moderate to High |
| FCAW (Flux-core) | 0.5-2.5 | High |
| SAW (Submerged arc) | 0.1-0.3 | Low (shielded by flux) |
Flux-core welding generates the most fume of any common process because the flux core decomposes at arc temperature, adding gaseous compounds to the already high particulate output. TIG generates the least fume because the tungsten electrode doesn’t transfer material to the weld (only the filler rod contributes fume) and the process operates at lower overall energy input.
Health Effects by Fume Component
Manganese
Found in: All steel welding fume. Manganese is a component of mild steel, stainless steel, and most welding consumables (wire, electrodes).
What it does: Chronic manganese exposure causes manganism, a progressive neurological disease that resembles Parkinson’s disease. Symptoms include:
- Tremor in the hands (often the earliest sign)
- Slowed movement and stiffness
- Balance and gait problems
- Difficulty with fine motor skills
- Mood changes, irritability, depression
- Cognitive impairment
Onset: Symptoms typically appear after 5-20 years of chronic occupational exposure, though higher exposures can accelerate onset. The damage is to the basal ganglia in the brain and is irreversible. Once neurological symptoms appear, they don’t improve even if exposure stops.
OSHA PEL: 5 mg/m3 as a ceiling limit (never to be exceeded). ACGIH TLV: 0.02 mg/m3 for the respirable fraction (reflects more recent research and is 250 times stricter than OSHA’s limit). Many welding scenarios exceed even OSHA’s more lenient PEL without ventilation.
Hexavalent Chromium (Cr6+)
Found in: Stainless steel welding fume, chrome-moly steel fume, and some hard-facing welding consumables.
What it does: Hexavalent chromium is classified as a known human carcinogen by OSHA, IARC (Group 1), NTP, and EPA. Health effects include:
- Lung cancer (primary concern)
- Nasal and sinus cancer
- Kidney damage
- Respiratory sensitization (occupational asthma)
- Nasal septum perforation and ulceration
- Skin irritation and contact dermatitis
Onset: Cancer risk increases with cumulative exposure over years to decades. There is no established safe threshold for carcinogens. Any exposure contributes to increased lifetime cancer risk.
OSHA PEL: 5 micrograms/m3 as an 8-hour TWA. This is an extremely low limit. For context, 5 micrograms is 0.000005 grams. Most unprotected stainless steel welding operations generate exposures many times above this limit. OSHA’s hexavalent chromium standard (29 CFR 1910.1026) requires exposure assessment, engineering controls, respiratory protection, medical surveillance, and record keeping for workers exposed above the action level (2.5 micrograms/m3).
Zinc Oxide
Found in: Galvanized steel welding fume.
What it does: Zinc oxide fume inhalation causes metal fume fever (MFF), an acute flu-like illness. Symptoms include:
- Fever and chills (often delayed 4-12 hours after exposure)
- Severe muscle aches
- Nausea and headache
- Fatigue and weakness
- Chest tightness and cough
Onset: Hours after exposure. Symptoms typically resolve within 24-48 hours. Monday morning fever is a pattern where symptoms are worst after a weekend break (the body loses its short-term tolerance during days off). Repeated episodes may cause chronic respiratory effects, though the long-term consequences are less studied than manganese or chromium.
OSHA PEL: 5 mg/m3 as an 8-hour TWA for zinc oxide fume.
Cadmium
Found in: Cadmium-plated steel, some silver brazing alloys (silver solder containing cadmium).
What it does: Cadmium is extremely toxic, even in very small amounts.
- Acute exposure: severe lung damage (chemical pneumonitis), potentially fatal
- Chronic exposure: kidney damage (tubular dysfunction), emphysema, lung cancer
- IARC classification: Group 1 carcinogen
OSHA PEL: 5 micrograms/m3. Cadmium has its own comprehensive OSHA standard (29 CFR 1910.1027) with specific requirements for monitoring, controls, medical surveillance, and worker notification.
Critical warning: Never weld or braze cadmium-containing materials without specific engineering controls and supplied-air respiratory protection. Cadmium fume has caused deaths from single acute exposures.
Welding Gases
In addition to metal particulates, welding arcs produce hazardous gases:
| Gas | Source | Health Effect |
|---|---|---|
| Ozone (O3) | TIG and MIG arcs (UV breaks down O2) | Lung irritation, pulmonary edema at high concentrations |
| Nitrogen oxides (NOx) | All arc processes | Lung irritation, pulmonary edema |
| Carbon monoxide (CO) | CO2 shielded MIG, flux decomposition | Headache, dizziness, death at high concentrations |
| Phosgene (COCl2) | Welding near chlorinated solvents | Severe lung damage (potentially fatal) |
Phosgene warning: Welding near degreased parts that retain chlorinated solvent residue (trichloroethylene, perchloroethylene) generates phosgene gas, which is extremely toxic. Always ensure parts are thoroughly cleaned and dried of solvent residue before welding. Phosgene has a delayed onset (symptoms may not appear for 24-72 hours) and can be fatal.
Which Welders Are Most at Risk
Fume exposure risk depends on process, material, ventilation, and duration.
Highest risk:
- Flux-core welders working on stainless steel in enclosed spaces (high fume generation + hexavalent chromium + poor ventilation)
- Stick welders in confined spaces (ship hulls, tanks, vessels)
- Welders working on galvanized steel without extraction (acute metal fume fever)
- Maintenance welders who encounter unknown coatings and plating on repair work
Moderate risk:
- MIG welders in moderately ventilated shops (mild steel)
- Stick welders in open shops
- Pipe welders working with chrome-moly alloys
Lower risk (but not zero):
- TIG welders (lowest fume generation)
- Welders using source capture fume extraction
- Welders using half-face respirators with P100 filters
- Welders in well-ventilated outdoor environments
No risk is “no risk.” IARC’s 2017 reclassification of all welding fume to Group 1 carcinogen means that even mild steel welding fume at any exposure level contributes to cancer risk. The question isn’t whether fume exposure is harmful. It’s how much harm accumulates over a career.
OSHA Permissible Exposure Limits
| Substance | OSHA PEL (8-hr TWA unless noted) | ACGIH TLV (reference) |
|---|---|---|
| Total welding fume (PNOR) | 5 mg/m3 | N/A (component-specific) |
| Manganese | 5 mg/m3 (ceiling) | 0.02 mg/m3 (respirable) |
| Hexavalent chromium | 5 micrograms/m3 | 25 micrograms/m3 |
| Nickel (soluble) | 1 mg/m3 | 0.1 mg/m3 |
| Zinc oxide fume | 5 mg/m3 | 2 mg/m3 |
| Cadmium | 5 micrograms/m3 | 10 micrograms/m3 |
| Lead | 50 micrograms/m3 | 50 micrograms/m3 |
| Iron oxide fume | 10 mg/m3 | 5 mg/m3 |
| Ozone | 0.1 ppm | 0.05 ppm (heavy work) |
Note: OSHA PELs haven’t been updated significantly since 1971 for many substances. ACGIH TLVs are generally more protective and reflect current research. Some states (California, Washington, Michigan) have adopted stricter exposure limits than federal OSHA.
Protecting Yourself
Three layers of protection reduce fume exposure:
1. Engineering Controls (Source Capture)
Fume extraction at the source is the most effective control. A properly positioned extraction arm captures 90%+ of welding fume before it reaches the breathing zone. See our portable extractor guide and shop system guide.
2. Respiratory Protection
A half-face respirator with P100 filters removes 99.97% of the fume that reaches it. For stainless and galvanized work, OV/P100 combination cartridges add gas/vapor protection. See our respiratory protection guide.
3. Work Practices
- Position yourself upwind or crosswind of the fume plume when possible
- Don’t weld in confined spaces without supplied-air respiratory protection and continuous air monitoring
- Identify base metals and coatings before welding. Unknown materials require maximum protection
- Keep your head out of the fume plume. If you can see the fume, you’re breathing it
- Use the lowest heat input that produces an acceptable weld. Lower heat = lower fume generation
- Choose processes with lower fume generation when possible (TIG over flux-core for the same joint, for example)
The Career-Long Perspective
A welding career spans 30-40 years. Every shift of unprotected fume exposure adds to the cumulative dose that determines long-term health outcomes. A P100 respirator costs $35 for the facepiece and $40-80 per year in filters. A portable fume extractor costs $1,500-3,500.
Manganism treatment: there isn’t one. The neurological damage is permanent.
Lung cancer treatment: chemotherapy, radiation, surgery, and a 5-year survival rate that varies by stage at diagnosis.
The cost-benefit calculation is simple. Protect yourself now. Every shift matters because the damage accumulates silently for years before symptoms appear.
The Bottom Line
Welding fume is a confirmed carcinogen that also causes neurological damage, lung disease, and kidney damage. The risks are highest for stainless steel, galvanized steel, and cadmium-containing materials, but even mild steel fume is classified as carcinogenic.
Protect yourself with: Source capture fume extraction + respiratory protection + smart work practices. All three. Not one instead of the other.
If you take one thing from this article, let it be this: the old-school culture of welding without respiratory protection is killing welders slowly. The data is clear. The protection is available and affordable. Use it.
For fume extraction options, see our portable extractor guide and shop system guide. For respiratory protection, see our respirator guide. Browse the fume extractors hub for all our ventilation content.