Welding Fumes2

7/30/2019 Welding Fumes2

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2004 J.E. Spear Consulting, LLC

WELDING FUME AND GAS EXPOSURE

By Jerome E. Spear, CSP, CIH

A recent $1 million award by an Illinois jury to

a welder was the first plaintiff victory in a weldingrod failure-to-warn suit and many similar casesare expected to follow. In the case ofElam v. AOSmith et. al., the jury concluded that themanganese in welding fumes caused a 65-yearold worker to develop a neurological disordersimilar to Parkinsons disease (i.e., Manganism).Since there are more than 500,000 workersemployed in welding and related occupations inthe U.S. (Bureau of Labor Statistics) and another200,000 welders or more who are retired, there isa potential pool of more 700,000 who are (orpreviously have) been exposed to welding fumes

on a daily basis.

Welding produces various contaminants at asufficient rate to cause both short and long-termhealth effects if not properly controlled. Acomprehensive review (Antonini) ofepidemiological studies of welders indicates thata large number of welders experience some typeof respiratory illness (such as bronchitis, airwayirritation, lung function changes, and a possibleincrease in the incidence of lung cancer).Pulmonary infections may also increase in termsof severity, duration, and frequency amongwelders following exposure to welding while

studies have also associated chronic exposure tomanganese with a risk for Parkinsons disease.

The best way to mitigate the potential oflarge settlements is to provide documentedevidence that you have progressively madeefforts in controlling exposure to welding fumesand gases. The first step is to understand thepotential health effects and recognize the factorsthat affect a welders potential exposure towelding fumes and gases.

Health Effects

Welding fumes are very small particles thatare formed when the vaporized metal rapidlycondenses in air and are typically too small to beseen by the naked eye, but collectively, form avisible plume. The health effects associated withmetal fumes depend on the specific metalspresent in the fumes but may range from short-term illnesses, such as metal fume fever (i.e., flu-

like symptoms), to long-term lung damage and/or

neurological disorders, such as lung cancerand/or Parkinsons disease. Figure 1 includesthe most common welding fume constituents andtheir associated health effects.

Gases are alsogenerated fromwelding, which mayinclude carbonmonoxide, ozone,and nitrogen oxides.Carbon monoxide(CO) is an odorless,colorless gas thatmay be formed bythe incompletecombustion of theelectrode covering or

flux and by the use of carbon dioxide (CO2) as ashielding gas. Overexposure to CO inhibits thebodys red blood cells to sufficiently carry oxygento other tissues within the body, whichsubsequently results in asphyxiation. Weldingdoes not normally generate CO at high enoughlevels to be a concern; however, high levels ofcarbon monoxide may potentially accumulate

when welding or air arc gouging in confinedspaces. There is also a potential of an oxygen-deficient atmosphere if welding inside of aconfined or enclosed space if an inert gas (suchas argon) is used as the shielding gas.

Ozone, nitrogen dioxide and nitric oxide areproduced by the interaction of ultraviolet light(from the welding arc) with the surrounding air.These compounds are irritating to the eyes, noseand throat. High exposures can also cause fluidin the lungs and other long-term pulmonaryillnesses.

If the metal has been degreased with achlorinated solvent, other airborne gases (suchas phosgene, hydrogen chloride, chlorine gas,etc.) may be produced. These gases generallycause irritation to the eyes, nose and respiratorysystem and symptoms may be delayed.


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Figure 1 Common Constituents in Welding Fumes

Metal

Constituent

Common Source(s) Health Effect(s)

Aluminum Component of some alloys (such as Inconel, copper, zinc,steel, copper, zinc, steel, magnesium, brass, and filler materials).

Lung damage, irritation

Beryll ium Hardening agent found in copper, magnesium, and aluminumalloys. Cancer (lung), berylliosis

Cadmium May be contained in plated materials and/or zinc alloys andsometimes used i n the manufacture of fluxes in flux-coredelectrodes.

Kidney damage

Chromium Contained in most stainless steel and high-alloy materials. Alsoused as plating material.

Irritation, dermatitis, li ver, kidney, respiratory,cancer (hexavalent chromium insolublecompounds)

Copper Included in alloys such as Monel, brass, bronze. Irritation, damage to the gastrointestinal tract, metalfume fever

Fluorides Common ingredient in electrode coatings and f lux mater ial forboth low- and high-alloy steels.

Irritation, bone damage, fluorosis

Iron The major contaminant in all steel-welding processes. Siderosis (i.e., pigmentation of the lungs)

Lead Common in solder, brass and bronze alloys. May also becontained in the primer/coating on steels.

Central nervous system, blood, kidney,reproductive

Magnesium Found in light metal alloys. Irritation, metal fume fever

Manganese Contained in most welding processes. Central nervous system, lung damage,reproductive

Molybdenum Contained in some steel alloys, stainless steel, and nickel alloys. Irritation, lung damage, central nervous system

Nickel Contained in stainless steel, Inconel, Monel, Hastelloy andother high-alloy materials, welding rods, and plated steel.

Dermatitis, pneumoconiosis, central nervoussystem, cancer, lung damage

Silicon Present in most welding consumables. Irritation, fever

Tin Used in some solder alloys and bronzes. Stannosis (i.e., benign lung disease), centralnervous system, irritation, immunotoxicity

Titanium Common ingredient in many f lux-cored electrodes and in thecoating of covered electrodes.

Lung damage

Vanadium May be contained in some steel alloys, stainless steel, and nickelalloys.

Irritation, lung damage

Zinc Common component of galvanized and coated metal. Metal fume fever (ACGIH, Antonini)

Common Welding Processes and

Fume Generation Rates

The type of welding process is directlyrelated to the amount of fumes and gases thatare generated. Therefore, it is important to havea basic understanding of the welding process inorder to assess the risk of exposure.

Shielded Metal Arc Welding (SMAW,

stick welding) is commonly used for carbonsteel welding and low alloy welding. In SMAW,the electrode is held manually, and the electricarc flows between the electrode and the basemetal. The electrode is covered with a fluxmaterial, which provides a shielding gas for theweld to help minimize impurities. The electrodeis consumed in the process, and the filler metalcontributes to the weld. SMAW can produce high

levels of metal fume and fluoride exposure;however, stick welding is considered to have littlepotential for generating ozone, nitric oxide andnitrogen dioxide.

Gas Metal Arc Welding (GMAW) ormetal inert gas (MIG) welding is typically used formost types of metal and is faster than SMAW.This process involves the flow of an electric arcbetween the base metal and a continuouslyspool-fed consumable electrode. Shielding gasis supplied externally; hence, the electrodetypically has no flux coating or core. AlthoughGMAW requires a higher electrical current thanSMAW, GMAW produces fewer fumes since theelectrode has no fluxing agents. However, due tothe intense current levels, GMAW producessignificant levels of ozone and nitrogen oxides.


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Flux Core Arc Welding (FCAW) is usedfor carbon steels, low alloy steels and stainlesssteels. This welding process has similarities toboth SMAW and GMAW. The consumableelectrode is continuously fed from a spool and anelectric arc flows between the electrode and base

metal. The electrode wire has a central corecontaining fluxing agents and additional shieldinggas may be supplied externally. This weldingprocess generates a substantial amount of fumedue to the high electrical currents and the flux-cored electrode. However, FCAW generates littleozone, nitric oxide and nitrogen dioxide.

Gas Tungsten Arc Welding (GTAW) isalso known as tungsten inert gas (TIG) welding.GTAW is used on metals such as aluminum,magnesium, carbon steel, stainless steel, brass,silver and copper-nickel alloys. This techniqueuses a non-consumable tungsten electrode. The

filler metal is fed manually and the shielding gasis supplied externally. High electrical currentsare used, which causes this process to producesignificant levels of ozone, nitric oxide andnitrogen dioxide.

Submerged Arc Welding (SAW) isanother common welding process used to weldthick plates of carbon steel and low alloy steels.In this welding process, the electric arc flowsbetween the base metal and a consumable wireelectrode; however, the arc is not visible since itis submerged under flux material. This flux

material keeps the fumes down and since the arcis not visible, there is little ozone, nitric oxide andnitrogen dioxide that is generated. The majorairborne hazard with SAW is the fluoridecompounds generated from the flux material.

The primary source of information whendetermining the components likely to be in thefume is the material safety data sheet of theconsumable welding electrode/wire. About 90 to95 percent of the fumes are generated from thefiller metal and flux coating/core of consumableelectrodes (Lyttle). Since the base metal weldpool is much cooler than the electrode tip, the

base metal contributes only a minor amount ofthe total fumes. However, the base metal maybe a significant factor of the fume exposure if themetal or surface residue contains a highly toxicsubstance (e.g., lead, cadmium, etc.). Also, the

AWS has conducted and published studies thatprovide the concentrations of selected metalconstituents in the fumes produced by variouswelding electrodes.

In addition to the welding technique, studieshave shown that the fume generation rate is alsoinfluenced by the following factors:

Electrical current: In general, the fumegeneration rate is exponentially proportionalto the current.

Arc voltage: The fume generation rategenerally increases when the arc voltageincreases.

Electrode diameter: The electrodediameter has a modest effect on the fumegeneration rate because of the differences involtage and current. In general, a smalldiameter electrode generates more fumethan a large diameter electrode.

Electrode angle: The angle of theelectrode to the workpiece has a slight (butunpredictable) affect on the fume generationrate.

Shielding gas: In gas-shielded arc welding,the fume generation rate tends to be greaterwhen CO2 (as opposed to argon) is used asthe shielding gas.

Speed of welding: As the welding rateincreases, the fume generation rateobviously increases.

Steady/current pulsed current

welding: Technology has advanced topower sources that have pulsing capabilities.Recent studies have shown that utilizing apulsing current during welding generates

fewer fumes than under steady currentwelding process.

In general, FCAW produces the greatest fumegeneration rate (for mild steel welding) followedby SMAW, GMAW and GTAW. See Figure 2 fora summary of the relative exposure potential bycommon welding processes.

Since most of the fumes are attributed to thewelding consumables, there has been a drive todevelop a number of low-fume consumables.The focus appears to be in the reformulation ofthe flux-cored wire to low-carbon strip materials

for the tube and less mineral compounds for thecore (Lyttle).

The above information should be consideredwhen performing an initial exposure assessment.The welding process and composition of thematerial (primarily the ingredients in the electrodeunless the steel is coated) should be the basis ofcategorizing similar exposure groups. High alloy


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materials tend to contain metals with loweroccupational exposure limits (such as chromium,nickel, copper, etc.). The similar exposuregroups can be further defined by the specifictask, position of the workpiece (in relation to thewelders breathing zone), presence or absence oflocal exhaust ventilation and/or other work-related factors.

References

American Conference of Governmental IndustrialHygienists (ACGIH). Threshold Limit Values for

Chemical Substances & Biological Exposure Indices.Cincinnati, OH: ACGIH, 2004.

Antonini, J. Health Effects of Welding.Critical Reviews in Toxicology. 33(1)(2003): 61-103.

Lyttle, K. (2004, March/April). OptimizingConsumable Selection Increases Productivity,

Decreases Fumes. Gases & WeldingDistribution. March/April 2004: 45-47.

U.S. Department of Labor, Bureau of LaborStatistics. < www.bls.gov>.

Figure 2 Exposure Potential of Common Welding Processes

Jerome E. Spear, CSP, CIH19314 Timber Ridge Drive, Suite 100Magnolia, Texas 77355Phone (281) 252-0005Fax (281) [email protected]

FCAW

Many fumes are generateddue to the high current but

the fumes causes low levelsof ozone and nitrogenoxides to be generated.

SMAW

Although low current is uthe flux causes much of fume but low levels of ozand nitrogen oxides aregenerated.

GMAW

The high current and no flux causes little fumes tobe generated but causes high levels of ozone andnitrogen oxides to be generated.

GTAW

Due to no flux, a minimal amount offumes is generated but the intensecurrent causes high levels of ozone andnitrogen oxides to be generated.
http://www.bls.gov/http://www.bls.gov/mailto:[email protected]:[email protected]://www.bls.gov/

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