Welding Fumes Profile

Welding Fumes Profile


  • A complex mixture of fine particles and gases produced as a byproduct of welding activities
  • Associated cancers: Lung cancer
  • Most important route of exposure: Inhalation
  • Primary use: Welding fumes are a byproduct, but welding itself is a skilled trade employed by many industry sectors in Canada
  • Occupational exposures: Approx. 333,000 Canadians are exposed to welding fumes at work, primarily in the construction and manufacturing sector
  • Environmental exposures: Home exposures to hobbyists who use welding
  • Fast fact: The composition of welding fumes varies according to the materials and welding process used.

General Information

Welding is a process that uses heat generated by electricity (e.g. arc welding) or fuel gases (e.g. oxyfuel welding) to fuse metal materials. As the metals are heated, they produce welding fumes composed of a mixture of fine particles and gases. These particles, which have an aerodynamic diameter of less than 1 µm, are capable of depositing in the deepest parts of the lungs. They consist of metal oxides, silicates and fluorides. Gases are generated by the welding process itself (e.g. use of shielding gases, oxyfuel welding) and include nitrogen oxides, carbon monoxide, and ozone.[1,2,3] Welding is performed in many industry sectors, including repair, construction, mining and manufacturing. [1,4,5,6] As such, exposure to welding fumes often occurs in conjunction with other common industrial exposures linked to cancer, such as asbestos and cleaning solvents.[1] Additionally, arc welding generates UV radiation.[7,8]

In 1989, the International Agency for Research on Cancer (IARC) classified welding fumes as probably carcinogenic to humans (Group 2A).[8,9] At the time, there was limited evidence of carcinogenicity in humans and inadequate evidence in animals. New evidence from observational and experimental studies has emerged and in 2017, IARC classified welding fumes as carcinogenic to humans (Group 1). This was based on sufficient evidence showing an increased risk of lung cancer in welders and other workers exposed to welding fumes, and limited evidence showing an increased risk of kidney cancer.[1,8]

Regulations and Guidelines

Occupational Exposure Limits (OEL)

Most Canadian jurisdictions do not have an occupational exposure limit (OEL) for total welding fumes, though OELs exist for constituents of welding fumes (e.g. nickel, chromium, beryllium).[10] Many jurisdictions apply the American Conference of Governmental Industrial Hygienists’ (ACGIH) guideline for Particles Not Otherwise Specified (PNOS). This guideline applies a different reference value depending on the size of the particles in the mixture, as illustrated in the following table:[10,11]

Exposure guidelines for particles not otherwise specified (PNOS)[10]

Particle Size FractionArea of deposition following inhalationCut point of particle-size selective air sampling at 50% collection efficiency*ACGIH Guideline for PNOS
InhalableAnywhere in the respiratory tract100 µmAirborne concentrations kept below 10 mg/m3
RespirableGas-exchange region of lungs4 µmAirborne concentrations kept below 3 mg/m3
ACGIH = American Conference of Governmental Industrial Hygienists
PNOS = Particles (insoluble or poorly soluble) Not Otherwise Specified
µm = micrometers
mg/m3 = milligrams per cubic meter *
ACGIH recommends using size-selective sampling heads when measuring airborne particulate matter. These sampling heads are designed to capture particles with an aerodynamic diameter that falls within a certain range. For example, a sampling head with a 50% collection efficiency of 4 µm means that 50% of the collected particulate matter will have an aerodynamic diameter of 4 µm or less.

The respirable size fraction poses a greater risk to health as these particles are capable of depositing in the deepest parts of the lungs.[12,13] In accordance, ACGIH recommends that airborne concentrations of PNOS be kept below 3 mg/m3 for the respirable fraction and below 10 mg/m3 for the inhalable fraction.[10] These guidelines are intended for substances that have low toxicity, however. For this reason it is often more appropriate to analyze the constituents in welding fumes individually.

Occupational exposure limits[10,14,15,16,17,18,19,20,21,22,23,24,25,26,27]

Canadian JurisdictionsOEL (mg/m3)
Canada Labour Code, MB, ON, NB, PE, NS, NL10 [pnos, i, twa]; 3 [pnos, r, twa]
BC, AB10 [pnos, t, twa]; 3 [pnos, r, twa]
SK10 [pnos, i, twa]; 20 [pnos, i, stel]; 3 [pnos, r, twa]; 6 [pnos, r, stel]
QC10 [pnos, t, twa]
NU5 [wf, twa]; 10 [wf, stel]
YT5 [wf, twa]; 5 [wf, stel]
NT10 [pnos, i, twa]; 20 [pnos, i, stel]; 3 [pnos, r, twa]; 6 [pnos, r, stel]; 5 [wf, twa]; 10 [wf, stel]
Other JurisdictionsOEL (mg/m3)
ACGIH 2020 TLV10 [pnos, i, twa]; 3 [pnos, r, twa]
mg/m3 = milligrams per cubic meter
pnos = particles (insoluble or poorly soluble) not otherwise specified
i = inhalable fraction
twa = time weighted average (8 hours)
r = respirable fraction
t = total dust
stel = short term exposure limit (15 min. maximum)
wf = welding fumes
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value

Main Uses

Welding fumes are produced as a byproduct of welding activities. While many industry sectors use the process to join metal materials, there is no specific use for welding fumes. There are over 70 different welding processes, each having a specific application. The most common processes include shielded metal arc welding, gas tungsten arc welding, and oxyfuel gas welding.[1,4,28]

Production in Canada

Almost all industry sectors in Canada employ welders, including repair, construction, manufacturing, oil and gas, agriculture, and the service industry.[1,4,5,6] Many workers also perform welding activities without having the official job title of a welder (e.g. construction or agricultural workers who weld intermittently but would not be classified as welders, automobile mechanics, and some artists).[1]

Environmental Exposures Overview

In the environment, the primary route of exposure is by inhaling welding fumes produced during hobby, artisan, or home welding projects. This includes a variety of activities, such as creating metal sculptures, or performing basic repairs on motor vehicles and other mechanical equipment. Typically, welding is performed in a home garage, workshop, or residential outdoor space.[29] Today, many welding courses and online resources are readily available to the general public, and welding equipment can be purchased at hardware stores. However, the number of welding hobbyists in Canada is difficult to estimate due to a lack of available data.

Occupational Exposures Overview

CAREX Canada estimates that approximately 333,000 Canadians are exposed to welding fumes in their workplaces. The industries with the highest number of exposed workers are machinery and equipment repair and maintenance, building equipment contractors, and automotive repair and maintenance. The largest occupational groups exposed to welding fumes are welders and related machine operators, construction trades helpers and labourers, and automotive service technicians, truck and bus mechanics and mechanical repairers. The magnitude of exposure to welding fumes is influenced by many factors, including:[2,3,30]

  • The type of welding process (e.g. arc or gas welding)
  • The composition of the welding rod
  • The type of filler materials and base metals used
  • The type of coatings present
  • The setting in which welding is performed (e.g. open area or a confined space)
  • Type of ventilation in the workspace (e.g. mechanical, local, natural or no ventilation)
  • The work practices of the welder (e.g. use of personal protective equipment, removal of coatings, cleaning surfaces, working upwind when welding outdoors)

According to the Burden of Occupational Cancer in Canada project, occupational exposure to welding fumes and welding lead to approximately 310 lung cancers and 15 ocular melanomas each year in Canada respectively, based on past exposures (1961-2001).[31,32] This amounts to 1.3% of lung cancer cases and 5.4% of ocular melanomas diagnosed annually. Most occupational lung cancers associated with welding fumes occur among workers in the manufacturing sector. These cancers also occur among workers in the trade, other services, and construction sectors. Work-related exposure to welding fumes resulted in approximately $308 million in costs for newly diagnosed lung cancer cases in 2011.[32]

For detailed estimates of exposure to welding fumes, see the occupational exposures tab.


1. International Agency for Research on Cancer (IARC). Monograph summary, Volume 118 (2018)
2. Canadian Centre for Occupational Health and Safety. Welding – Fumes and Gases (2018)
4. Canadian Centre for Occupational Health and Safety. Welder fact sheet (2018)
5. Skills Ontario. Trades Profile: Welding (2019)
7. International Agency for Research on Cancer (IARC). Monograph summary, Volume 100D (2012)
8. Guha N, Loomis D, Guyton KZ, Grosse Y, El Ghissassi F, Bouvard V, Benbrahim-Tallaa L, Vilahur N, Muller K, Straif K, International Agency for Research on Cancer Monograph Working Group. “Carcinogenicity of welding, molybdenum trioxide, and indium tin oxide.” Lancet Oncol 2017; 18(5): 581-582.
9. International Agency for Research on Cancer (IARC). Monograph summary, Volume 49 (1990)
10. American Industrial Hygienist Conference (ACGIH). Threshold Limit Values for Chemical Substances and Physical Agents & Biological Exposure Indices (2020). ACGIH: Cincinnati, OH.
11. National Institute for Occupational Safety and Health (NIOSH). Welding fumes (OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Projects) (1989)
19. Government of Newfoundland and Labrador. Regulation 5,12 Occupational Health and Safety Regulations (2018)
20. Government of the Northwest Territories. Occupational Health and Safety Regulations, R-039-2015 (2020) (PDF)
22. The Canadian Legal Information Institute (CanLII). Government of Nunavut’s Occupational Health and Safety Regulations, Nu Reg 003-2016 (2010)
24. Government of Prince Edward Island. Occupational Health and Safety Act Regulations Chapter 0-1 (2013) (PDF)
26. Government of Saskatchewan. The Occupational Health and Safety Regulations, 1996 (2016) (PDF)
27. The Canadian Legal Information Institute (CanLII). Yukon’s Occupational Health Regulations, O.I.C. 1986/164 (2020) (PDF)
28. Canadian Centre for Occupational Health and Safety. Welding – Overview of Types and Hazards (2018)
30. WorkSafeBC. Welding gases & fumes (2019)
31. Labrèche F, Kim J, Song C, Pahwa M, Calvin BG, Arrandale VH, McLeod CB, Peters CE, Lavoué J, Davies HW, Nicol AM. “The current burden of cancer attributable to occupational exposures in Canada.” Prev Med 2019;122:128-39.
32. Occupational Cancer Research Centre. Burden of Occupational Cancer (2017)

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