Welding fume exposure and determinants in German male

Welding fume exposure and determinants in German male

Welding fume exposure
and determinants in
German male welders
Benjamin Kendzia1, Anne Lotz1, Martin Lehnert1, Tobias Weiss1 , Katarzyna Gawrych1, Evelyn Heinze1, Ying Chen1,
Rainer Van Gelder2, Markus Berges2, Thomas Brüning1, Beate Pesch1 and the WELDOX Study Group
1
2
Institute for Prevention and Occupational Medicine of the German Social Accident Insurance, Institute of the Ruhr-Universität Bochum (IPA), Bochum, Germany
Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA), Sankt Augustin, Germany
Results and discussion
Introduction and objectives
Various studies investigated exposure to particulate mass among welders (Hobson et al. 2011).
However, studies measuring respirable welding
fumes in the breathing zone of welders are rare.
The aim of this analysis was to explore exposure
to respirable welding fumes and potential influencing factors of the airborne concentrations.
Methods
Conclusions
» Among 241 measurements of respirable
welding fumes from the WELDOX study, 90
data points were below LOD.
» Two different approaches were applied to
deal with data below LOD, Tobit regression
and imputation. They revealed similar
effect estimates for potential determinants
of the exposure to welding fume and
yielded a good model fit.
» The welding process was the major
determinant, with high concentrations
for FCAW and considerably lower
concentrations for TIG in terms of
particulate mass. Efficient LEV reduced
exposure, working in a confined space
increased the exposure significantly.
Figure 1: Welder working in confined space
Figure 2: Welder using efficient local exhaust
ventilation
Table 1: Potential determinants of exposure to respirable welding fume (N=215; excluding users
of powered air-purifying respirators)
Factor
N
Tobit regression
Exp(ȕ)
95% CI
N<LOD
Intercept [mg/m³]
Gas metal arc welding
Flux-cored arc welding
Tungsten intert gas welding
Shielded metal arc welding
Miscellaneous
Multiple imputation
Exp(ȕ)
95% CI
2.84
2.30 - 3.50
2.54
1.87 - 3.44
78
42
66
17
12
9
0
47
8
1
1.00
2.17
0.18
1.02
1.12
1.57 - 3.00
0.12 - 0.27
0.60 - 1.73
0.66 - 1.90
1.00
2.36
0.16
0.87
1.39
1.49 - 3.72
0.10 - 0.27
0.41 - 1.86
0.66 - 2.93
Mild steel
Stainless steel
Miscellaneous
79
109
27
5
57
3
1.00
0.49
0.90
0.36 - 0.68
0.63 - 1.29
1.00
0.45
0.95
0.29 - 0.70
0.58 - 1.57
Non-confined space
Confined space
193
22
65
0
1.00
1.63
1.10 - 2.42
1.00
1.83
1.06 - 3.14
Non-efficient local exhaust ventilation
167
47
1.00
0.32 - 0.63
1.00
48
18
0.45
0.32 - 0.63
0.41
Efficient local exhaust ventilation
0.73A
Model fit R²
Major determinant of the concentrations
was the type of welding process. The use
of flux-cored wire in gas metal arc welding (FCAW) was estimated to increase
the concentration in comparison with gas
metal arc welding with solid wire (GMAW)
by a factor of 2.17 (95% CI 1.57-3.00) using
Tobit regression and by 2.36 (95% CI 1.493.72) using imputation. Tungsten inert gas
welding (TIG) was associated with 0.18 or
0.16 fold lower exposure levels than with
GMAW in both models. Welding of stainless steel was associated with significant lower concentrations in comparison
to mild steel. Efficient LEV reduced the
concentrations and welding in confined
space increased exposure levels with significant effects in both approaches.
References
• Efron B (1979) Bootstrap methods; another look at the jacksknife. Ann Statistics 7: 1-26
• Harel O (2009) The estimation of R2 and adjusted R2 in incomplete data sets using multiple imputation. Journal of Applied Statistics 36: 1109-1118
• Hobson A, Seixas N, Sterling D, Racette BA (2011) Estimation of particulate mass and manganese exposure levels among welders. Ann Occup Hyg 55: 113-125
• Laitila T (1993) A pseudo-R2 measure for limited and qualitative dependent variable Models. Journal of Econometrics 56: 341-356
• Lubin JH, Colt JS, Camann D, Davis S, Cerhan JR, Severson RK, Bernstein L, Hartge P (2004) Epidemiologic evaluation of measurement data in the presence of
detection limits. Environ Health Perspect 112: 1691-1696
• Tobin J (1958) Estimation of relationship for limited dependent variables. Econometrica 26: 24-36
0.25 - 0.66
0.64B
A Laitila 1993, B Harel 2009
" !$#%
WELDOX was conducted as nationwide study
among welders in German industries. Personal
sampling of respirable welding fumes was carried out in 241 welders. Exposure to particle-size
specific welding fumes was determined by personal sampling in the breathing zone inside the
helmets during a working shift. Experienced technicians documented the welding techniques, the
workplace characteristics, and other exposurerelated conditions. In addition, photos were taken
to document the workplaces. Ninety measurements of respirable welding fumes were below
limit of detection (LOD). Therefore, we applied
Tobit regression (Tobin 1958) and imputations of
values <LOD with a maximum likelihood estimation method (Lubin et al. 2004, Efron 1979). Assuming an equal probability distribution below and
above LOD we imputed values <LOD randomly
from a log-normal distribution (1000 runs). We
presented regression coefficients for the welding
processes, materials, working in confined space,
and using efficient local exhaust ventilation (LEV)
at the original scale.
Figure 3: Respirable welding fume by welding
process.
FCAW =
GMAW =
TIG =
SMAW =
Flux-cored arc welding,
Gas metal arc welding,
Tungsten intert gas welding,
Shielded metal arc welding
Acknowledgement:
WELDOX was financially supported by the German Social Accident Insurance (DGUV).