APPROACHES TO WELDING

EXPOSURE ASSESSMENT

AND CONTROL Noah Seixas

Marissa Baker

Chris Simpson

Boris Reiss

Jeff Walls

Chris Warner

Jane Pouzou

Department of Environmental and

Occupational Health Sciences

University of Washington

Outline

• Manganese and Welding

• Mn content of welding fume

• Particle size distributions/deposition

• What the literature tells us about exposure

• Hobson, Liu and Pesche

• What the literature tells us about Biomarkers

• Our biomarker study

• Design

• Preliminary Findings

• Potential new directions

• Hair

• LA-ICPMS

• Recommendations for going forward

Welding Processes

• “A joining process that produces coalescence of materials by heating

them to the welding temperature, with or without the application of

pressure alone and with or without the use of filler metal.” Jefferson’s Welding Encyclopedia, 18th Edition”, Robert L. O’Brien, Editor, American Welding Society, Miami, FL

• >80 Welding Process Types

• Oxy-Fuel (Welding or Cutting)

• Arc, or SMAW (Shielded Metal Arc)

• MIG or GMAW (Gas Metal Inert Gas)

• FCAW (Flux-Cored Arc)

• TIG (Gas Tungsten Arc)

Welding Risks Overview • Estimated 3 million welders and cutters globally

• About 400,000 in the US; 140,000 full time • Estimates 800,000 full-time welders worldwide • Most from small employers

• Risks • Acute Injuries

• Musculoskeletal

• Electrical

• Burns

• UV

• Gasses

• CO, CO2, Asphyxiants

• Fume

• Fe, Mn, Cr6, Ni, Cd, Zn

• From:

• Base metal,

• Filler material

• Fluxing agents

• Coatings (Pb, epoxies, etc.)

Fume-related health effects

• Respiratory

• COPD

• Siderosis

• Asthma

• Cancer

• Especially lung

• Presumably from Cr6, Ni in stainless steels

• Neurological

• “Manganism”

• Parkinson’s like syndrome

• Are welders at increased risk of Parkinson’s Disease?

• At what level of exposure are neurological effects present?

Standards and Guidelines

Agency Welding Fume Manganese ACGIH 5 mg/m3 (rescinded) 0.1 mg/m3 Inhalable

0.02 mg/m3 Respirable (proposed)

NIOSH ALARA 1 mg/m3 OSHA 5 mg/m3 (rescinded) 5 mg/m3 (C)

Ger. MAK

(TRGS 900)

0.2 mg/m3 Inhalable

0.02 mg/m3 Respirable

(proposed)

EU 2010

(SCOEL/SUM/127)

0.2 mg/m3 inhalable

0.05 mg/m3 respirable

Exposure Assessment Approaches

• Epidemiologic exposure assessment

• e.g., Years worked as welder

• Industrial Hygiene Air Sampling

• Personal exposure monitoring in breathing zone

• “Total”, Inhalable or Respirable fraction sampling?

• Inside or Outside the hood?

• Analyte

• Particulate Mass Concentration

• Metal-specific concentration

• Biomonitoring? - especially for Mn

• Urine

• Blood*

• Hair

• Nails

• Brain

SEM of SMAW fume on polycarbonate filters

Particle Size Distributions

of Welding Fume

From: Pesche, et al, 2012

(1-1 line added by eye)

From: Hewett, 1995

PSDs: Primary vs. Agglomerates

• Richman et al, Journal of Aerosol Science, 2011 • 10 GMAW samples

• STEM microscopy

• Energy dispersive X-ray spectroscopy by primary particle size

• Primary particles CMD: 6.6 +3.0 nm

• Agglomerates: CMD: 105 +19 nm

• Mn Abundance (relative to Fe): 6 (+3)% • Only slight increase in Mn content with increasing PS

• Conclusion: • Respirable or inhalable fraction samples are adequate:

• multiple fractions add very little information

• Primary particle size may be relevant to potential dissolution, absorption, translocation and dose

11

Figure 6

Paired Total Fume Samples Inside Helmet and Outside Helmet with PVC Filters

y = 1.067x + 0.5607

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

22.00

24.00

26.00

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00

Total Fume Inside Helmet

To

tal

Fu

me O

uts

ide H

elm

et

(Total Fume Inside Helmet with PVC, Total Fume Outside Helmet with PVC)Linear ((Total Fume Inside Helmet with PVC, Total Fume Outside Helmet with PVC))

Monitoring:

Inside Vs Outside?

• Some studies show lower levels inside helmet

• Inside Vs. outside (via PVC & gravimetric)

• Corr. Coeff.: 0.97

• Range inside: • 6.6 mg/m3 to 19.0 mg/m3.

• Range outside: • 7.1 mg/m3 to 23.0 mg/m3.

From Harris, AIHCE PDC, 2008

Overall R2=0.51

Coef. CI β

Oxy 0.004 (0.001, 0.007) 0.010

Stick 0.016 (0.012, 0.020) 0.020

MIG 0.018 (-0.008, 0.043) 0.032

TIG 0.003 (-0.006, 0.012) 0.014

Dual Shield 0.036 (0.018, 0.053) 0.023

Inner Shield 0.014 (-0.004, 0.033) 0.009

Cutting/Grinding 0.001 (-0.001, 0.003) 0.017

Mn vs. Particulate by welding type

Estimating exposure

• Requires quantitative understanding of

• Factors associated with exposure

• Including interactions between factors

• Requires a comprehensive dataset

• Large number of samples

• Covering all conditions/processes one might encounter

• Data on all pertinent factors

• Repeated measures if possible

• “Exposure Determinants Modeling”

Factors Associated with (and predictive of)

Mn Exposure among welders

Hobson Liu Pesche

Dataset Published Literature Literature, NIOSH HHEs,

TWI

Novel dataset,

German Industry

Years Covered 1967-2009 1966-2005 2007-2009

# Samples 1957

(in 60 means)

697 241

Sample Types Personal Personal/Area Personal

Sample Duration Full shift, >6hr ST, FS: <>1hour 1.5-5 hours

Size Fraction Total Total Respirable

Dependent Variable ln(Mn) or ln(PM) ln(Mn) ln(Mn)

Model Regression on means Mixed Model on

samples

Regression on

samples

Number of Parameters 9 26 8

Overall Mean (SD)

(mg/m3)

0.26 (+0.36) 0.502 (+1.49) 0.062

(IQR, 0.008-0.320)

Modeled Mn (mg/m3) Exposure Estimates

What about biomonitoring?

• For specific constituents (e.g., metals, e.g., Mn)

• Benefits

• Closer to biological target

• Focused on individual-specific dose

• Accounts for deposition, absorption, etc.

• Accounts for duration and intensity

• Accounts for PPE use

• Disadvantages

• Individual-only

• Toxicokinetics confound interpretation

• Biological regulation may obscure relationships

• Background levels obscure low levels

Smith et al. 2007

Blood Mn v. Mn in air

by exposure groups,

after Luccini, 1999

Apostoli et al. 2000

Blood Mn v. Mn in air

Selected studies:

Air vs. Blood Mn

Mean MnB vs. Mn A

(n=24 papers)

Mean MnB vs. ln Average MnA

(n=22 papers)

Limitations of current biomarker studies

• Mostly cross-sectional

• Poor temporal specificity in relation between airborne and

biomarker measures

• No unexposed baseline

• LODs are problematic

• Especially for urine and plasma measures

• Relationship between Mn and Fe status poorly addressed

Mn biomarkers in welding school students • Enrolled and tested at baseline

• Little prior exposure

• Monitoring over 5 quarter sequence

• Daily, Weekly, Across Quarter

• Target 80 Student Welders • Air, Blood, Urine, Hair and MRI (subset)

• Temporally specific modeling for each biomarker

Air Mn concentration by weld type

Cross shift changes in MnB by Measured

Air Manganese Exposure

Cross week change in MnB by Estimated

Cumulative Air Manganese Exposure

Cross Quarter (3 mo) by Estimated

Cumulative Air Manganese Exposure

Hair as a biomarker

Background

Pro:

Hair has been used as biomarker

Growth rate is estimated to be about 1 cm / month

Cons:

Not all substances have an affinity for hair – i.e. Manganese?

Descriptive statistics of log transformed hair levels

(mg/g) by duration in program

N=34 N=22 N=11 N=8 N=4

(0,90] (90,180] (270,360] (360,inf] (180,270]

LA-ICPMS for

time-resolved

metals in hair

From Stadlbauer, et al,

Anal Bioanal Chem, 2005.

Welding Fume Deposition on Hair

Suggested Directions for Mn Exposure

Assessment • Air Sampling

• Mn and Particulate Mass

• Combined with

• Task-specific exposure model

• Detailed work task and exposure questionnaire

• Biological monitoring • Blood

• Promising?

• Hair/nails by LA-ICPMS shows promise

• In vivo neutron activation analysis also may be possible

MOTIVATION • Shipyard welders routinely receive exposures to weld fume

that exceed occupational limits • Important determinants: weld method & type of space

• Barriers to effective fume control • Dynamic work environment • Work in spaces that restrict air movement

• Practical general ventilation guidelines relevant to shipyard welding are limited • OSHA General Industry

• 2,000 cfm/worker in spaces < 10,000 ft3

• Unproven and unlikely to be effective overall

• Local Exhaust Ventilation • Ineffective in most dynamic processes

• Can’t effectively position

• Too close affects weld quality

31

Shipyard Ventilation Study

AIMS:

1. Develop a set of general ventilation guidelines

2. Teach the guidelines to shipyard welders

3. Evaluate the adoption of the guidelines

32

Study Shipyard Vigor Industrial (formerly Todd Pacific Shipyard)

33

USS Polar Star USS Davis Nobel Kulluk Nobel Discoverer WA State Ferry

Recommended ventilation guidelines 34

Recommended ventilation guidelines

35

Shipyard observations

• Randomly observe welders for 10 minutes

• Measure BZ particular exposure (dataRAM)

• Observe

• Space characteristics

• Size, configuration, enclosure, location of welding

• Welding processes

• Ventilation characteristics

• Exhaust vs. Supply

• # mechanical units, estimate CFM

• Proximity

• Local, regional, general

• Mixing/Cross-draft

• “Short-circuiting”

36

Exposure by use of ventilation

Early results

37

FCAW SMAW and MIG Oxy-gas welding/cutting Space

volume

n GM GSD n GM GSD n GM GSD ft3

All observations 17 3.6 3.0 7 0.6 4.3 5 0.5 2.8 4690

Type of ventilation

No ventilation 9 4.1 3.9 1 0.4 . 2 0.2 1.0 2470

Exhaust 6 3.3 2.2 6 0.6 4.8 3 1.0 2.5 7680

Dilution 2 2.4 2.1 0 . . 0 . . 2980

Area Mixing Unmixed 14 4.0 3.1 5 0.8 4.7 5 0.5 2.8 5860

Mixed 3 2.1 1.8 2 0.3 3.8 0 . . 1480

Volumetric flow rate

(Qt)

Low (90-1000 ft3/min) 5 2.9 2.6 4 0.4 5.1 1 2.5 . 5070

High (1100-2550

ft3/min) 3 3.2 1.2 2 2.2 1.0 2 0.6 1.7

9430

Space ventilation rate

Low (0.01-0.50 ACM) 5 4.6 1.6 4 0.7 5.1 2 1.5 2.1 10300

High ACM (1.0-2.8

ACM) 3 1.5 1.7 2 0.5 7.8 1 0.4 .

580

Summary

• Welding is a common industrial process

• Welding processes have numerous hazards

• Including metals with significant toxicity

• Exposures are high and largely uncontrolled

• Exposure assessment

• Continue to rely largely on air monitoring

• Both particulate mass and metal-specific

• Biomonitoring of great interest, but a largely research enterprise

• Except for specific issues, e.g., lead

• Exposure control

• Ventilation has limited impact, but needs increased attention/use

• Respiratory protection continues to play an important role

Discussion