The effects of arc welding on cardio-respiratory health in shipyard workers.

202 Pages·2015·8.68 MB·English

by  Andrea Marongiu

Imperial College London
National Heart and Lung Institute
Department of Respiratory Epidemiology, Occupational Medicine and
Public Health
MRC-PHE Centre for Environment and Health

Arc welding and the risk of airways and cardiovascular
diseases: WELSHIP study

by

Andrea Marongiu

A thesis submitted for the degree of Doctor of Philosophy
Dedication
In memory of my father Vittorio

‘No sentía cà moria càntu impàru ancora bollia’
Declaration

I herewith certify that this dissertation is my original work and that all material included that is not
my own work has been properly acknowledged.

Copyright declaration
The copyright of this thesis rests with the author and is made available under a Creative Commons
Attribution Non-Commercial No Derivatives licence. Researchers are free to copy, distribute or
transmit the thesis on the condition that they attribute it, that they do not use it for commercial
purposes and that they do not alter, transform or build upon it. For any reuse or redistribution,
researchers must make clear to others the licence terms of this work.
Abstract

Globally there are around 10 million workers who routinely weld and are exposed to a metal fume
aerosol of small particles of largely metal oxides and gases. Their medium- and long-term
cardiorespiratory risks are incompletely understood.

This thesis describes a programme of novel research carried out in a large Middle Eastern
shipyard. Four studies were completed. First, a systematic review of published cross-sectional
surveys (N: 38) in welders were identified; a meta-analyses of 34 publications showed a clear
excess of asthma (OR 1.65; 95% CI 1.14, 2.37) and chronic bronchitis (OR 1.92; 1.50, 2.45) that
could not be explained by smoking. In contrast, there was remarkably, little summary evidence of
deficits in lung function in welders.

Second, a cross-sectional survey of shipyard workers (N: 529, response rate 93%) showed no
evidence of any decrements in lung or cardiac function in welders but suggested that symptoms of
respiratory infections in winter were more common in this group (OR 2.65; 1.22, 5.78) than in
matched referent workers. Support for this novel finding came from the third study, of clinical
records held by the yard’s medical centre over an eleven-year period (N: 15,954). Consultations
for respiratory infections were 72% higher in welders compared to office workers; there was a
clear exposure-response relationship across workers with different intensities of welding. The
fourth study, of a panel of 50 shipyard workers (response rate 100%) suggested a small cross-shift
decline in lung function and increase in arterial stiffness.

These findings suggest, for the first time, that welders are susceptible to a wide range of
respiratory infections. High quality, collaborative research in this setting is feasible; future studies
could usefully examine in more detail – including microbiological - the relationship between
welding fume exposure and respiratory infections. The potential health-benefits to the global
community of welders are substantial.

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Acknowledgements
I would like to thank my supervisors Prof Paul Cullinan, Dr Cosetta Minelli, Dr Jo Zram and Dr
Cristina Canova, their encouragement, patience and willingness to share their experience has been
invaluable for the completion of this very ambitious project. I am particularly indebted to Prof Paul
Cullinan for the opportunity.

Without the enthusiasm, commitment, hard work and professionalism demonstrated by the
WELSHIP team in Dubai this research would have not been a success. I am grateful to Dr Omer
Imtiaz Hasan, Ms Anila Ali, Mr Sharoon Bakhsh, Mr Bobby George and Mr Nabeel Irfan for being
outstanding colleagues and remarkable friends.

I would like to thank Magda Wheatley for her time in helping with the arrangement of payments
to the study participants and to Stephanie MacNeill for her support and never-ending
encouragement. Many thanks go to Susie Schofield for her statistical advice and help with the
systematic literature review duplicate extraction of data.

For their time and willingness to share their knowledge, I wish to thank a panel of experts: Dr
David Green and Dr Ben Barratt for the collection of environmental exposure data and Dr Andre
Amaral for the collection of bio-samples. I am particularly grateful to Dr Martin Cosgrove for
sharing his experience and enthusiasm on welding and for his advice during the writing up stage.

I am grateful to the MRC-PHE Centre for Environment and Health for awarding me a studentship
and to DryDocks World Dubai for their partnership and commitment while conducting the
WELSHIP study.

Finally I would like to express how deeply indebted I am to my family and friends, Marian for
always being there, Bianca and Shanae for giving me shelter while in Dubai and for being good
listeners and Louise for proofreading the final draft. Above all, I am thankful to my mother Lalla,
Piero, Jason and Tess whose constant, unconditional love and support got me through tough
times.

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Abbreviations
ACGIH American Conference Of Governmental Hygienists
AIx Augmentation Index
Al Aluminium
aPWV Aortic Pulse Wave Velocity
ATS American Thoracic Society
bBP Brachial Blood Pressure
bDBP Brachial Diastolic Blood Pressure
bMAP Brachial Mean Arterial Pressure
BP Blood Pressure
bSBP Brachial Systolic Blood Pressure
cBP Central (Aortic) Blood Pressure
cDBP Central (Aortic) Brachial Diastolic Blood Pressure
COPD Chronic Obstructive Pulmonary Disease
cSBP Central Systolic Blood Pressure
DDW-D DryDocks World-Dubai
DIP Desquamative Interstitial Pneumonia
FCAW Flux-Core Arc Welding
FEF25-75% Forced Expiratory Flow At 25–75% Of Forced Vital Capacity
FEV Forced Expiratory Volume In 1 Second
1
FFR Fume Formation Rate
FP Fractional Polynomials
FVC Forced Vital Capacity
GMAW Gas Metal Arc Welding - MIG/MAG
GTAW Gas Tungsten Arc Welding - See TIG
HRV Heart Rate Variability
IHD Ischaemic Heart Disease
IPD Invasive Pneumococcal Disease
IRR Incidence Rate Ratio
LEV Local Exhaust Ventilation
LRT Lower Respiratory Tract
LRTI Lower Respiratory Tract Infection
MFF Metal Fume Fever
MI Myocardial Infarction
MIG/MAG Metal Inert Gas/Metal Active Gas - See GMAW
μm Micrometre
MMA Manual Metal Arc Welding - See SMAW Or Stick
MS Mild Steel
OH Occupational Health
OR Odds Ratio
P P-Value
PEFR Peak Expiratory Flow Rate
PM Particulate Matter
PPE Personal Protective Equipment
PWA Pulse Wave Analysis
PWV Pulse Wave Velocity
SBP Systolic Blood Pressure
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SD Standard Deviation
SDNN Standard Deviation Of Normal-To-Normal Intervals Between Heartbeats
SE Standard Error
SMAW Shielded Metal Arc Welding - See MMA or Stick
SS Stainless Steel
Stick welding Welding With Flux Coated Consumable Electrode - See SMAW or MMA
TIG Tungsten Inert Gas Welding - See GTAW
TLV® Threshold Limit Values Set By ACGIH
UAE United Arab Emirates
UFP Ultrafine Particles (<0.1 μm)
ULCC Ultra Large Crude Carrier
URT Upper Respiratory Tract
URTI Upper Respiratory Tract Infection
VLCC Very Large Crude Carrier
WHR Waist-To-Hip Ratio
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Contents
DEDICATION II
DECLARATION III
COPYRIGHT DECLARATION III
ABSTRACT IV
ACKNOWLEDGEMENTS V
ABBREVIATIONS VI
CHAPTER 1: BACKGROUND 14
1.1 ARC WELDING 14
1.1.1 Metal dust, fine particles and welding fume 15
1.1.2 Health and arc welding: an overview 16
1.2 RESEARCH HYPOTHESIS 17
1.3 AIMS AND OBJECTIVES 17
1.4 DATA SOURCES AND FIELDWORK 17
1.5 THESIS PLAN 21
1.6 RESEARCH IN A ‘REAL WORLD’ SETTING 21
CHAPTER 2: SYSTEMATIC LITERATURE REVIEW AND META-ANALYSIS ON LUNG FUNCTION AND
OBSTRUCTIVE PULMONARY DISEASE IN ARC WELDERS 23
2.1 METHODS 23
2.1.1 Search strategy 23
2.1.2 Inclusion and exclusion criteria 24
2.1.3 Outcome measures 24
2.1.4 Data extraction 25
2.1.5 Statistical analyses 25
2.2 RESULTS 36
2.2.1 Characteristics of the studies included in the review 36
2.2.2 Meta-analysis results for lung function 38
2.2.3 Meta-analysis results for respiratory symptoms 41
2.2.4 Publication and small studies bias: asymmetry analysis 45
2.3 DISCUSSION 48
2.3.1 Lung function 48
2.3.2 Asthma and respiratory symptoms 49
2.3.3 Respiratory health of shipyard welders 50
2.3.4 Limitations 50
2.3.5 Strengths 51
2.4 CONCLUSION 52
CHAPTER 3: CROSS-SECTIONAL SURVEY 54
3.1 RESEARCH AIM AND OBJECTIVES 54
3.2 METHODS 54
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3.2.1 Fieldworkers’ training and survey pilot 54
3.2.2 Sample selection and sample size 55
3.2.3 Survey process, data collection and storage 58
3.2.4 Data analysis 63
3.3 RESULTS 66
3.3.1 Sample characteristics 66
3.3.2 Cardiorespiratory health 70
3.3.3 Secondary analyses results 74
3.4 DISCUSSION 77
3.5 LIMITATIONS 83
3.6 CONCLUSION AND FUTURE RESEARCH 84
CHAPTER 4: RESPIRATORY INFECTIONS AND WELDING FUME EXPOSURE - AN EXAMINATION OF A
WORKPLACE DATABASE. 86
4.1 RESEARCH AIM AND OBJECTIVES 86
4.2 METHODOLOGY 86
4.2.1 Target population, employment and medical data 86
4.2.2 Employment records data handling 87
4.2.3 Medical records data handling 89
4.2.4 Recoding of diagnosis for the 2000-2005 period 90
4.2.5 Diagnostic code assignment database 92
4.2.6 Data analyses 94
4.3 RESULTS 96
4.3.1 Primary analysis results 97
4.3.2 Secondary analysis results 99
4.4 DISCUSSION AND CONCLUSIONS 100
4.5 LIMITATIONS 101
4.6 CONCLUSIONS 101
CHAPTER 5: PANEL (PILOT) STUDY 103
5.1 RESEARCH AIMS AND OBJECTIVES 103
5.2 METHODS 103
5.2.1 Sample selection and target population 103
5.2.2 Survey timeline and fieldworkers’ training 104
5.2.3 Study process, data collection and storage 105
5.2.4 Statistical analysis 111
5.3 RESULTS 113
5.3.1 Sample characteristics 113
5.3.2 Cardiorespiratory health analyses 115
5.3.3 Overview of remaining collected outcomes 119
5.4 DISCUSSION 120
5.5 LIMITATIONS 123
5.6 CONCLUSION 124
CHAPTER 6: CONCLUSIONS 126
REFERENCES 128
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APPENDICES 138
A.2.1 SEARCH STRATEGY 138
A.2.2 ESTIMATES EXTRACTION FORMS 141
A.2.3 ADDITIONAL FOREST PLOTS FOR LUNG FUNCTION MEASURES AND RESPIRATORY SYMPTOMS 143
A.2.4 ADDITIONAL FUNNEL PLOTS FOR LUNG FUNCTION MEASURES AND RESPIRATORY SYMPTOMS WITH PSEUDO 95%
CONFIDENCE LIMITS AND ASYMMETRY TESTING 161
A.3.1 CROSS-SECTIONAL SURVEY DOCUMENTS AND QUESTIONNAIRE 167
A.3.2 CROSS-SECTIONAL SURVEY FREQUENCY MATCHING 174
A.3.3 CROSS-SECTIONAL SURVEY DIAGRAM 175
A.3.4 SENSITIVITY ANALYSIS ADDITIONAL TABLES 176
A.4.1 COMPLETE LIST OF ALL DIAGNOSIS AND DIAGNOSTIC CODES 178
A.4.2 EXAMPLE OF RECODED DIAGNOSIS FOR THE SECOND INDEX LIST: 2000-2004 MEDICAL RECORDS 186
A.5.1 PANEL STUDY DOCUMENTS AND QUESTIONNAIRE 187
A.5.2 PANEL STUDY SAMPLING FRAME 194
A.5.3 PANEL STUDY DIAGRAM 196
A.5.4 SOP FOR HANDLING BLOOD SAMPLES 197
A.5.5 SUMMARY TABLE OF RESPIRATORY PANEL STUDIES 199

Tables
Chapter 1
Table 1.1: Particulate fraction, particulate matter (PM) size range and respiratory tract ............................................... 15
Chapter 2
Table 2.1 Summary table of all cross-sectional studies ordered by industry included in the systematic review .............. 29
Table 2.2 Outcomes’ summary table of all cross-sectional studies included in the meta-analysis ordered by industry .. 35
Chapter 3
Table 3.1 Exposure groups and job titles .......................................................................................................................... 57
Table 3.2 Outcomes and covariates considered as a priori confounders .......................................................................... 65
Table 3.3 Sample characteristics by exposure groups ...................................................................................................... 66
Table 3.4 Cardiorespiratory health by exposure groups ................................................................................................... 68
Table 3.5 Respiratory symptoms by exposure stratified by season .................................................................................. 70
Table 3.6 Multiple logistic and linear regression of binary and continuous cardiorespiratory outcomes (welders vs. non-
welder) .............................................................................................................................................................................. 71
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