Welding Processes and Welding Processes and Exposure AssessmentExposure Assessment
Stephanie R. Carter, CIHStephanie R. Carter, CIHUniversity of Washington/Central Washington University of Washington/Central Washington
UniversityUniversity
CIHC 16CIHC 16thth Annual Conference Annual ConferenceDecember 4, 2006December 4, 2006
San Diego, CASan Diego, CA
IntroductionIntroduction
Need for weldersNeed for welders ““Where have All the Welders Gone, As Where have All the Welders Gone, As
Manufacturing and Repair Boom?” Manufacturing and Repair Boom?” – Average age of welders = 54 Average age of welders = 54
– 10% decline in number of welders since 10% decline in number of welders since 20042004
– By 2010, demand for welders may By 2010, demand for welders may outweigh supply by 200,000outweigh supply by 200,000
• Need more trained weldersNeed more trained welders
Wall Street Journal 8/15/2006Wall Street Journal 8/15/2006
IntroductionIntroduction
In 2020, welding In 2020, welding will continue to be will continue to be the preferred the preferred method of method of joining….joining…. Increases inIncreases in
– Plastics, composites, Plastics, composites, new alloysnew alloys
– AluminumAluminum– Robotic weldingRobotic welding– FCAW, GMAWFCAW, GMAW
R&D challenges R&D challenges (heavy industry)(heavy industry) Make the workplace Make the workplace
more attractive by more attractive by eliminating fumes, eliminating fumes, noise, and radiationnoise, and radiation
Materials to replace Materials to replace Cr and Ni (Mn?)Cr and Ni (Mn?)
Welding Technology Roadmap: Vision, AWS/EWI (2000)Welding Technology Roadmap: Vision, AWS/EWI (2000)
IntroductionIntroduction
Consumable Consumable electrodes electrodes purchased in 1991:purchased in 1991: SMAW – 45%SMAW – 45%
GMAW – 34%GMAW – 34%
FCAW – 17%FCAW – 17%
SAW – 4%SAW – 4%
One California One California shipyardshipyard SMAW – 50%SMAW – 50%
GMAW/GTAW – 5%GMAW/GTAW – 5%
FCAW – 20%FCAW – 20%
SAW – 25%SAW – 25%
Development of Particulate and Hazardous Emission Factors for Electric Arc Welding (AP-42,Section 12.19), 1994
IntroductionIntroduction
Emerging IssuesEmerging Issues Health EffectsHealth Effects
Sampling/AnalysisSampling/Analysis
Process Determinants of ExposureProcess Determinants of Exposure
ControlsControls
Health EffectsHealth Effects
PulmonaryPulmonary Decreased lung Decreased lung
functionfunction
AsthmaAsthma
Lung cancerLung cancer
Increase in Increase in infectionsinfections
OtherOther Metal fume feverMetal fume fever
ConjunctivitisConjunctivitis
Nervous systemNervous system
Ocular Melanoma/skin Ocular Melanoma/skin cancercancer
FatalityFatality
Health EffectsHealth Effects
Exposure fatalityExposure fatality 2003 fatality in 2003 fatality in
WA/Oregon WA/Oregon
Oregon sales repOregon sales rep
Applied chromium Applied chromium and nickel based and nickel based thermal sprays for thermal sprays for 2 days in WA2 days in WA
Health EffectsHealth EffectsUV and weldingUV and welding
Case-control studies link ocular Case-control studies link ocular malignancy with weldingmalignancy with welding
Arc welding produces full spectrum of Arc welding produces full spectrum of UVRUVR– Short distances from sourceShort distances from source
ControlsControls– Clothing and sunscreenClothing and sunscreen– Aluminum welders need highest protectionAluminum welders need highest protection
Dixon, A., B. Dixon. MJA 2004; 181:155-157
Health EffectsHealth EffectsUV and weldingUV and welding
Welding helmet allows UV in from sides and top, Welding helmet allows UV in from sides and top, problem forproblem for– Highly reflective areas, multiple weldersHighly reflective areas, multiple welders
Exposure assessment (compared to ACGIH MPE)Exposure assessment (compared to ACGIH MPE)
OculOcularar
ClothingClothing
WeldersWelders 4 – 4 – 5X5X
3000X3000X
Nearby Nearby workersworkers
9X9X 13X13X
AreaArea 5.5X5.5X
Tenkata,T. Collins, M. AIHAJ 58(1)33-38
Ten
kata
,T. C
olli
ns,
M. A
IHA
J 58(1
)33
-38
Sampling and AnalysisSampling and Analysis Questions of oldQuestions of old
Placement of Placement of samplersampler
Grinding influenceGrinding influence
AnalysisAnalysis– GravimetricGravimetric– ElementalElemental
• AsAs• PbPb• CoCo• Etc…Etc…
Newer questionsNewer questions Hexavalent Hexavalent
chromiumchromium
Particle sizeParticle size
AnalysisAnalysis
RadiationRadiation
Sampling and AnalysisSampling and Analysis
Evaluation of the allowed samplers and Evaluation of the allowed samplers and procedures procedures (ISO 10882-1:2001)(ISO 10882-1:2001) Different samplers UK, German, HSEDifferent samplers UK, German, HSE
– French, Danish (similar to U.S.)French, Danish (similar to U.S.)
Left or right side positioningLeft or right side positioning Lapel vs helmet samplingLapel vs helmet sampling Grinding effectsGrinding effects Surrogate measures of fume compositionSurrogate measures of fume composition
Chung, et al., Applied Occupational and Chung, et al., Applied Occupational and Environmental Hygiene, 14((107-118), 1999.Environmental Hygiene, 14((107-118), 1999.
Sampling and AnalysisSampling and Analysis
Sampling and AnalysisSampling and Analysis
Results (Chung, et al)Results (Chung, et al) Little difference between samplersLittle difference between samplers Variable effect from right vs. leftVariable effect from right vs. left All collected grinding dustAll collected grinding dust Percent of individual contaminants in fume Percent of individual contaminants in fume
different than MSDSdifferent than MSDS Lapel samplingLapel sampling
– Larger ratios than in helmet sampling Larger ratios than in helmet sampling – Collected more grinding dustCollected more grinding dust
• Except for HSEExcept for HSE
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2Ratio to D
um
my
UK French Danish HSE German
R-BZ LBZ R-LP L-LP
Comparison of Air Samplers to Comparison of Air Samplers to DummyDummy
Sampling and AnalysisSampling and Analysis Hexavalent ChromiumHexavalent Chromium
OSHA-215 Revision 2OSHA-215 Revision 2– Cr(VI) samples collected on PVC filters from Cr(VI) samples collected on PVC filters from
welding operations must be analyzed within 8 welding operations must be analyzed within 8 days of samplingdays of sampling
NIOSH Methods (7605 and 7703)NIOSH Methods (7605 and 7703)– Higher recoveries of CrHigher recoveries of CrVIVI compared to OSHA-215 compared to OSHA-215
although not statistically significant although not statistically significant – NIOSH 7703 Chromium, Hexavalent, by Field-NIOSH 7703 Chromium, Hexavalent, by Field-
Portable SpectrophotometryPortable Spectrophotometry• No evidence of CrNo evidence of CrVIVI reduction to Cr reduction to CrIII III perhaps related perhaps related
to ultrasonic extractionto ultrasonic extraction
QA/QCQA/QC
Sampling and AnalysisSampling and AnalysisNanoparticles or Nanoparticles or
ultrafine particlesultrafine particles <100 nm<100 nm Arise in workplace Arise in workplace
throughthrough– NucleationNucleation– CombustionCombustion– Saturated vaporsSaturated vapors– Mechanical Mechanical
processesprocesses– Nanophase Nanophase
technologytechnology
Deposition and Deposition and alveolar clearance alveolar clearance differencesdifferences Negligible in terms Negligible in terms
of mass of mass concentrationconcentration
Better to look at Better to look at surface area or surface area or numbernumber
No personal No personal monitoring devices monitoring devices availableavailable– Estimation of SSA by Estimation of SSA by
respirable samplingrespirable sampling
Sampling and AnalysisSampling and Analysis
Particle sizeParticle size Number or surface area of particles vs. Number or surface area of particles vs.
massmass– Ultrafine particles may have greater Ultrafine particles may have greater
biological effect than an equivalent mass of biological effect than an equivalent mass of larger particleslarger particles
– Count median diameter of SMAW = 120 nmCount median diameter of SMAW = 120 nm– Mass median diameter of SMAW = 590 nmMass median diameter of SMAW = 590 nm
Clusters behavior determined by AED, Clusters behavior determined by AED, butbut– Primary particles more surface areaPrimary particles more surface area
Hewitt,P. AIHAJ,56(2)128-143
Sampling and AnalysisSampling and AnalysisProcessProcess SSA (mSSA (m22/g)/g)
SMAW-MSSMAW-MS 18.018.0
SMAW-SSSMAW-SS 19.419.4
GMAW-MSGMAW-MS 27.227.2
GMAW-SSGMAW-SS 39.639.6
ProcessProcess AED(µm)AED(µm)
SMAW-MSSMAW-MS 0.590.59
SMAW-SSSMAW-SS 0.460.46
GMAW-MSGMAW-MS 0.250.25
GMAW-SSGMAW-SS 0.250.25
Total lung deposition of GMAW estimated Total lung deposition of GMAW estimated to be 60% greater than for SMAWto be 60% greater than for SMAW GMAW deliver 3 times the particle surface GMAW deliver 3 times the particle surface
area to lungsarea to lungs Particle surface chemistry and lung clearance Particle surface chemistry and lung clearance
rates vary as wellrates vary as wellHewitt,P. AIHAJ,56(2)128-143
Sampling and AnalysisSampling and Analysis Analysis questionsAnalysis questions
On-site analysisOn-site analysis– Portable micro-Portable micro-
balances balances • (0.1 mg possible)(0.1 mg possible)
– Portable XRFPortable XRF• Non-destructive, Non-destructive,
filters, wipes, bulksfilters, wipes, bulks• Acceptable LOD Acceptable LOD
except for Cobalt except for Cobalt and Arsenic with and Arsenic with TWA samples (400 TWA samples (400 L)L)
• No speciationNo speciation
Analysis Analysis questionsquestions Laboratory Laboratory
analysisanalysis– PIXE analysisPIXE analysis– ICP-AES/MSICP-AES/MS
• Digestion Digestion protocolprotocol
Nygren,O. JEM,2002, 4,623-627
Sampling and AnalysisSampling and Analysis
Thorium and GTAWThorium and GTAW Tungsten electrodes can contain 1-4% Tungsten electrodes can contain 1-4%
ThoriumThorium– 2% most common (WT-20)2% most common (WT-20)
• 232232Th, Th, 228228Th, Th, 230230ThTh
– Alpha emitterAlpha emitter
Exposure potential Exposure potential – ““Vapors” during welding Vapors” during welding – Grinding to shape tipGrinding to shape tip Gafvert,T. et.al, RPD,103(4),349-
257(2003)
Sampling and AnalysisSampling and Analysis
WeldingWelding DC < 3mBq/mDC < 3mBq/m33
AC < 10 mBq/mAC < 10 mBq/m33
– Up to 141 mBq/mUp to 141 mBq/m33 for inexperiencedfor inexperienced
Total dust, Total dust, outside helmetoutside helmet
GrindingGrinding 5 mBq/m5 mBq/m33
Respirable dustRespirable dust
Dose estimatesDose estimates Welding Welding
– 0.3 to 1 mSv0.3 to 1 mSv
GrindingGrinding– 10 µSv to 63 10 µSv to 63
µSvµSv
Gafvert, et al. Radiation Protection Dosimeter, 103(4)pp.349-357 (2003)
Sampling and AnalysisSampling and Analysis
TIG welding and ThoriumTIG welding and Thorium ControlsControls
– LEVLEV– No contact with open cuts or woundsNo contact with open cuts or wounds– Clean-upClean-up– No eating, drinking, smokingNo eating, drinking, smoking– Thorium-free tungsten electrodeThorium-free tungsten electrode
• CeOCeO22 (2%) or La (2%) or La22OO3 3 (1-2%), Zr (1%), Pure (1-2%), Zr (1%), Pure TungstenTungsten
The Proper Selection and Preparation of Tungsten Electrodes for Arc Welding, www.diamondground.com
Quantity and particle size of Quantity and particle size of emissions dependsemissions depends
Welding process Welding process itself plus other itself plus other variablesvariables FluxFlux
Gas CompositionGas Composition
Operating Operating conditionsconditions Travel speedTravel speed VoltageVoltage CurrentCurrent Arc lengthArc length PolarityPolarity Welding positionWelding position Electrode angleElectrode angle Deposition rateDeposition rate
By E
lect
rode/P
roce
ssB
y E
lect
rode/P
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ss
Develo
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Part
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Haza
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Emissions by Shielding Emissions by Shielding GasGas
0102030405060708090
FG
R(%
)
C5 C25 CO2 M2 Ar
FCAW(E309LT Solid wire ER309L
2001 Ship Production Symposium, EWI
Effects on Particle SizeEffects on Particle Size
Zim
mer,
A. JE
M, 2
002(4
),628
-632
Welding Emissions ControlWelding Emissions ControlProcess SelectionProcess Selection
from SMAW to GMAWfrom SMAW to GMAW Fume extraction Fume extraction
welding gunwelding gun
Engineering controlsEngineering controls Local exhaustLocal exhaust DilutionDilution
Process modificationProcess modification Power variation Power variation
(GMAW)(GMAW)
Low-fume electrodesLow-fume electrodes
Composition changes Composition changes to minimize spatter or to minimize spatter or to shift metals to slagto shift metals to slag
Controls – Process Controls – Process SelectionSelection
0 0.2 0.4 0.6 0.8 1 1.2
SMAW
GMAW steady
GMAW Pulsed
FCAW CO2
FCAW Ar/CO2
GTAW
SAW
Fume Generation Rate (g/min)
Fiore,S. Welding Journal, 2006, August, 38-42.
Controls – Fume Extractions Controls – Fume Extractions GunsGuns
0
5
10
15
20
25
30
Per
sona
l exp
osur
es
(mg/
m3)
for
FCAW
Total Fe Mn
Analyte
Guns No guns Unknown Walla
ce, M
., e
t al A
pplie
d O
EH
(200
1),
16(8
),771
-779
Effects of VentilationEffects of Ventilation
0
5
10
Tota
l fu
me
(mg/m
3)
Tank Indoors
Type 1
Type 2
None
Elemental with ventilationElemental with ventilation Arsenic – 2 of 16 exceeded OSHA PELArsenic – 2 of 16 exceeded OSHA PEL Hexavalent chromium – Reduced exposures, Hexavalent chromium – Reduced exposures,
but still above 50 µg/mbut still above 50 µg/m33
Wallace, M., et al(2002), Applied OHE 17(3),145-151
Effect of Ventilation – Effect of Ventilation – Confined SpacesConfined Spaces
0
50
100
Tota
l fum
e
(mg/
m3)
Welder 1 Welder 2 Welder 3
LEVDV
Success of either ventilation depends onSuccess of either ventilation depends on Work practices Work practices
– backing out backing out – backing inbacking in
Equipment maintenanceEquipment maintenance
Wurzelbacher,S. Applied OEH, 17(11):735-740(2002)
Welding Processes and Welding Processes and ExposureExposure
Effect of pulsed powerEffect of pulsed power
0
1
2
3
4
5
6
Ave
rage W
eld
ing
Fum
e(m
g/m
3)
Plant A Plant B Plant C All
Normal Pulsed Area
Wallace, et. Al Applied OEH,16(2), 93-97, 2001
Hex chromium formation (in MIG Hex chromium formation (in MIG welding)welding)
Court
est
y John D
ennis
ControlsControlsProcess modificationProcess modification
Various strategies explored over 10 yearsVarious strategies explored over 10 years– 1. Adding some substance to:1. Adding some substance to:
• a) the consumable to react with Oa) the consumable to react with O33 before it reacts before it reacts with Cr with Cr
• b) increase the Ob) increase the O33 destroying wavelengths of UV destroying wavelengths of UV • c) reduce the Oc) reduce the O33 forming wavelengths of UV forming wavelengths of UV
– 2.2. Using a first or second shield gas or a gas in Using a first or second shield gas or a gas in the macro environment of the arc to the macro environment of the arc to
• a) absorb Oa) absorb O33 forming wavelengths forming wavelengths • b) react rapidly with Ob) react rapidly with O33. .
– 3. Use a suitable ‘shroud’ to block UV 3. Use a suitable ‘shroud’ to block UV transmissiontransmission
– 4. Engineering modification of welding equipment 4. Engineering modification of welding equipment and welding parameters to produce weld and welding parameters to produce weld conditions which emit little Cr (VI).conditions which emit little Cr (VI).
Court
est
y John D
ennis
Courtesty John Dennis
Courtesty John Dennis
Dennis JH et al. Control of Exposure to Hexavalent Chromium and Ozone in Gas Metal Arc Welding of Stainless Steels by use of a Secondary Shield Gas. Annals of Occupational Hygiene 46:1, 43-48. 2002.
Dennis JH et al. Control of Occupational Exposure to Hexavalent Chromium and Ozone in Tubular Wire Arc-welding Processes by Replacement of Potassium by Lithium or by Addition of Zinc. Annals of Occupational Hygiene 46:1, 33-42. 2002
ControlsControlsPractical IssuesPractical Issues
Creativity/ownershipCreativity/ownership SkillsSkills
– To modifyTo modify
Persistence Persistence – ““not sufficiently applicable to moving work”not sufficiently applicable to moving work”
The futureThe future Thinking outside the boxThinking outside the box
Light Sensing Self-Adjusting Light Sensing Self-Adjusting HoodHood
Ojim
a,
J. JO
H,4
5(2
):12
5-1
26
(200
3)
TurkemTurkem et. al, AWS, 2005 et. al, AWS, 2005
TurkemTurkem et. al, AWS, 2005 et. al, AWS, 2005
