Welding, Brazing, and Soldering

How are they portrayed in the occupational medicine literature?

1. The NIOSH Pocket Guide has an entry for Welding fumes, but none for brazing or soldering fumes.
2. ACGIH had an entry for "Welding fumes, not otherwise specified" published in 2001 with a TLV of 5 mg/m3, "total" aerosol, but that was deleted and no longer appears in 2018 TLVs and BEIs. The 2001 document makes no mention of "soldering" or "brazing."
3. IARC published in 2018 "Welding, Molybdenum Trioxide, and Indium Tin Oxide" in which welding was linked to lung cancer:

   Welders routinely perform other hot work processes, such as brazing, soldering, cutting, and gauging [gouging]. Brazing and soldering are similar, although brazing is conducted at a higher temperature and can therefore use stronger filler metals. Unlike welding, where the two metals being joined typically need to be similar and are melted to join them together, soldering and brazing involve using a filler metal with a melting temperature below the metals being joined; they can therefore be used to join dissimilar metals. [IARC Monograph 118, p. 43]

   Studies of risk estimates of occupations which may involve unspecific and infrequent welding (such as pipefitters, plumbers, and solderers), are excluded from this review; the frequency of welding in these occupations is not normally clear, and the groupings are too broad to meaningfully evaluate exposure as a welder. Studies that reported only broad occupational aggregations, combining welding with related occupations, were also excluded as they lack specificity for welding. [IARC Monograph 118, p. 89]

   Welding is a broad term for the process of joining metals through coalescence. Approximately 11 million people worldwide are estimated to have the occupational title of welder, and approximately 110 million workers (3% of the worldwide economically active population) may incur welding-related exposures in the workplace. Many types of welding are used in occupational settings, including oxyfuel (gas) and arc welding. Arc welding includes manual metal arc (MMA), gas metal arc (GMA), flux-cored arc (FCA), and gas tungsten arc (GTA) welding. Electric resistance (ER) welding is also used. Most welding is carried out on stainless steel (SS) and mild steel (MS). Welding results in concurrent exposures including welding fumes, gases, ionizing and non-ionizing radiation, and co-exposures such as asbestos and solvents. Welding fumes are produced when metals are heated above their melting point, vaporize, and condense into fumes of predominantly fine solid particles with an aerodynamic diameter of less than 1  µm. These fumes are a complex mixture of particles from the wire or electrode, base metal, or any coatings on the base metal. They consist mainly of metallic oxides, silicates, and fluorides. [IARC Monograph 118, p. 255]

   There is sufficient evidence in humans for the carcinogenicity of welding fumes. Welding fumes cause cancer of the lung. [IARC Monograph 118, p. 265]

4. Chapter 30 in Occupational & Environmental Medicine: Current Diagnosis and Treatment, 5th Ed. is entitled "Welding." In the fourth paragraph, the authors state, "Brazing and gas welding both generate metal fume. An acetylene torch is used to generate an intense flame. Exposure to cadmium oxide from cadmium-containing silver solder has caused acute lung injury and death after brazing in enclosed spaces. Similar consequences have occurred from generation of the oxides of nitrogen during gas welding. In all cases, improper ventilation was the critical factor in creating the hazard." [LaDou, p. 482] No entries in index for brazing or soldering.
5. In the "Bronchitis, chronic" chapter of Preventing Occupational Disease and Injury, David Christiani lists "welding operations" as one of the causes of chronic bronchitis. [Christiani, p. 133] No entries in index for brazing or soldering.
6. In "Hazards of Shipbuilding and Ship Repair" in Clinical Environmental Health and Toxic Exposures, the authors mention operations performed by "Welders" and various adverse effects of "Welding," but brazing and soldering are not mentioned. [Sullivan, p. 594-6] No entries in index for brazing or soldering.
7. In Textbook of Clinical Occupational and Environmental Medicine, 2nd Ed., welding and brazing are mentioned in the table of "Hazards associated with jobs, processes and tasks. [Rosenstock, p. 56] Welding has been associated with COPD. [Rosenstock, p. 323] Welders can develop benign pneumoconiosis. [Rosenstock, p. 410] Brazier's disease is another term for metal fume fever. [Rosenstock, p. 988] No entries in index for brazing or soldering.
8. In Occupational Disorders of the Lung: Recognition, Management, and Prevention, chapter 30 is entitled "Welding." The author writes in the introduction, "Given the potentially hazardous nature of some of the constituents of the fume, the ubiquitous nature of welding processes (with the work duties of an estimated 2-3 million people worldwide said to include some welding), and the extensive research literature on the health of welders, it would not be surprising for there to be a well-evidenced history of widespread acute and chronic adverse effects on respiratory health in welders and those in related trades. This is, however, not the case. While there is general agreement on acute effects, wide variation is found between the conclusions of studies of long-term effects." [Hendrick, p. 467] No entries in index for brazing or soldering.
9. In NIOSH Criteria for a Recommended Standard: Welding, Brazing, and Thermal Cutting published in1988, "Brazing is the process by which metals are heated and joined together by a molten filler metal at temperatures exceeding 450 deg C (840 deg F). Soldering, which is not included in this document, is similar to brazing, but it uses filler metals that have melting points below 450 deg C." [p. 25] In the Glossary, various forms of arc welding are mentioned. Also mentioned are "furnace brazing" and "torch brazing." 
10. In Recognition of Health Hazards in Industry, 2nd Ed., William Burgess outlines the hazards of welding in chapter 10. Brazing is included as one of 10 types of welding. "The technique of joining metals has much in common with soldering operations, but it is identified as a welding process by the American Welding Society. Brazing is defined as a technique for joining metals that are heated above 430 deg C (800 deg F), while soldering is conducted below that  point. The temperature of the operation is of major importance since it determines the vapor pressure of the metals that are heated and therefore the concentration of metal fumes to which the operator is exposed. . . . Brazing of small job lots that do not require close temperature control are routinely done with a torch. More critical, high-production operations are accomplished by dip techniques in a molten bath, in brazing furnaces using either an ammonia or hydrogen atmosphere, or by induction heating. . . . The exposure to fresh cadmium fumes during brazing of low-alloy steel, stainless steels, and nickel alloys has resulted in documented cases of occupational disease and represents the major hazard from these operations." [p. 189-90] The author says on page 186, "The principal hazard in gas welding in confined spaces is due to the formation of nitrogen dioxide." "Soldering in Electronics" is covered in chapter 22. "Since soft soldering is conducted at low temperature there is little hazard of significant lead exposures. . . . The handling of solder dross during cleanup and maintenance  may result in exposure to lead dust." [p. 382]

How are they portrayed in Haz-Map?

Welding, Brazing, and Soldering are three Processes linked to metals, respiratory irritants, allergens, and carbon monoxide. 

Welding fumes (not otherwise specified) is an Agent linked to "Lung cancer," "Pneumonitis, toxic," and "Pulmonary disease, chronic obstructive." Brazing and soldering fumes are not listed in Haz-Map as agents.

Hazardous Job Tasks	Diseases Associated with Job Task
Arc weld aluminum (arc)	Toxic pneumonitis; COPD
Arc weld stainless steel (arc)	Asthma; Chromium, chronic effects; COPD
Use manganese-containing welding rods (arc)	Manganese, chronic effects
Decompose chlorinated solvents by UV light or heat from welding (gas or arc)	Toxic pneumonitis
Gas or arc weld on galvanized metal (gas or arc)	Metal fume fever; Lead, chronic effects
Weld on metal painted with chlorinated polyester paint (gas or arc)	Asthma
Weld or machine on beryllium-containing alloys (arc)	Chronic beryllium disease
Heat or machine manganese alloys (arc)	Manganese, chronic effects
Heat, machine, or spray lead products (gas or arc)	Lead, chronic effects
Gas weld or cut in a confined space  (gas)	Toxic pneumonitis
Decompose fluoropolymers by welding, burning, brazing, or soldering (weld, braze, or solder)	Polymer fume fever
Heat or machine chromium alloys (arc)	Chromium, chronic effects
Heat or machine cobalt alloys (arc)	Asthma
Machine or weld on cadmium-alloyed or cadmium-plated steel (gas or arc)	Cadmium, chronic effects; Toxic pneumonitis; Acute tubular necrosis; Chronic renal failure;
Braze using cadmium-based solder (braze)	Cadmium, chronic effects; Toxic pneumonitis; Acute tubular necrosis; Chronic renal failure;
Use solder containing colophony, zinc chloride, ethanolamine, or ammonium chloride flux (solder)	Asthma
Weld mild steel (arc)	Asthma, Benign pneumoconiosis; COPD

See Brazing vs. Welding. Brazing operates at lower temperatures than welding.

This page from the American Welding Society suggests that brazers are choosing between "air-fuel" and "oxy-fuel," i.e., that brazing is a form of gas rather than arc welding. 

In Conclusion

Soldering and brazing do not cause the underlined diseases below because of their low temperatures compared to welding.

Soldering: Occupational asthma; Lead poisoning from exposure to dust if lead solder used;

Brazing: Polymer fume fever; Metal fume fever; Lead poisoning; Cadmium poisoning; Toxic pneumonitis, Acute tubular necrosis; Chronic renal failure;

Arc Welding: Occupational asthma; Toxic pneumonitis; Benign pneumoconiosis; Manganese poisoning; Lead poisoning; Chromium poisoning; Chronic beryllium disease; Polymer fume fever; Metal fume fever; Acute tubular necrosis; Chronic renal failure; COPD; Lung cancer;

Other Reference Material: Why Brazing Cannot Cause the Same Diseases as Welding

Metals	Melting Points (deg F)
Cadmium	609.9
Magnesium	1202
Aluminum	1221
Silver	1763
Copper	1984
Manganese	2275
Beryllium	2349
Steel	2500
Stainless steel	2500-2800
Nickel	2651
Iron	2795
Chromium	3465

 

Table 10.4 Brazing Filler Materials [Burgess, p. 190]

Base Metal to be Brazed	Brazing Filler Metals	Brazing Technique
Stainless steels	Silver alloys; Copper alloys;	Torch; Furnace
Aluminum	Aluminum-silicon alloys	Furnace
Magnesium	Magnesium alloys	Torch; Dip
Copper	Copper-phosphorus; Copper-zinc; Silver alloys;	All techniques
Nickel	Silver alloys; Copper alloys;	All techniques
Low-alloy steel	Silver alloys; Copper alloys; Nickel alloys;	All techniques

The vapor pressure of cadmium at 315 deg F is 0.000021 mm Hg with a cadmium concentration of 0.12 mg/m3. At 738 deg F, the vapor pressure is 1.0 and the cadmium concentration is 5900 mg/m3. [Burgess, p. 190] The IDLH of cadmium fume is 9 mg/m3. [NIOSH]

Arc welding melts both the welding rod and the base metal. Brazing melts only the filler material. It does not achieve high enough temperature to melt the base metal. Note that the diseases caused by arc welding (after melting manganese, beryllium, chromium, and steel) are not possible at brazing temperatures.

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