The study of Occupational risk factors and interventions for bakers' allergy and asthma among

318 Pages·2013·10.71 MB·English

by  Baatjies_ Roslynn

THE STUDY OF OCCUPATIONAL RISK
FACTORS AND INTERVENTIONS FOR
BAKER’S ALLERGY AND ASTHMA AMONG
SUPERMARKET BAKERY WORKERS

By
Roslynn Baatjies

Thesis presented for the degree of
Doctor of Philosophy
in the School of Public Health and Family Medicine
University of Cape Town

August 2013
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The copyright of this thesis vests in othe author. No
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published without full acknowledgement of the source.
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THE STUDY OF OCCUPATIONAL RISK FACTORS AND
INTERVENTIONS FOR BAKER’S ALLERGY AND
ASTHMA AMONG SUPERMARKET BAKERY WORKERS
By
Roslynn Baatjies

Thesis presented for the degree of
Doctor of Philosophy
in the School of Public Health and Family Medicine
University of Cape Town
August 2013

Supervisor: Professor Mohamed Fareed Jeebhay
Co-supervisors: Professor Dick Heederik and Dr Tim Meijster

This thesis is presented in fulfilment of the requirements for the degree of
Doctor of Philosophy (PhD) in the School of Public Health and Family
Medicine, Faculty of Health Sciences, University of Cape Town. The work on
which this thesis is based is original research and has not, in whole or in
part, been submitted for another degree at this or any other university. The
contents of this thesis are entirely the work of the candidate, or in the case of
multi-authored published papers, constitutes work for which the candidate
was the lead author. The contribution of the candidate to included multi-
authored papers is further delineated in the preface to the thesis and in the
introduction to each included paper as appropriate.

____________________________
Roslynn Baatjies
August 2013
ABSTRACT

Background: Baker’s asthma is the most serious manifestation of
occupational allergy among bakery workers. It is caused by IgE-mediated
sensitisation and subsequent allergic reaction in the airways to specific
occupational airborne allergens in flour or baking ingredients. Major aims of
this study were to:
characterise asthma phenotypes and environmental exposure to flour
allergens among bakers and modifying factors;
study associations between phenotype and environmental exposure
and identify potential modifying factors of this association;
determine the effectiveness of specific interventions in reducing
exposure and the risk of sensitisation or allergic respiratory disease.

Methods: A cross-sectional study was conducted among 517 bakery
workers employed in 31 supermarkets. Health outcomes were assessed
using a standardized questionnaire, immunological tests (sIgE, sIgG),
methacholine challenge test and fractional exhaled nitric oxide (FeNO).
Exposure assessment conducted pre- and post-intervention entailed
determination of inhalable concentration of particulate mass and specific
allergen levels. The intervention employed a group-randomised design to
evaluate dust control measures.

Results: Prevalence of probable occupational asthma (POA, 13%) was
higher than atopic (AA, 6%), non-atopic (NAA, 6%) and work-aggravated
asthma (WAA, 3%). Sensitisation to flour allergens was a major determinant
of elevated FeNO among bakers. Bread bakers had the highest dust
particulate (mean = 1.33 mg/m3) and allergen exposures. Exposure-
response relationships followed a bell-shaped curve, with the prevalence of
IgE- sensitisation, allergic symptoms and POA, increasing up to 10-15 µg/m3
of airborne wheat allergen concentrations before declining. The association
for IgE sensitization was not modified by IgG4 to wheat. The overall effect of
the intervention revealed a 50% decrease in mean flour dust, wheat allergen
and rye exposures in bakeries.

Conclusion: Occupational asthma is the most common phenotype among
supermarket bakery workers, with sensitisation to cereal flour allergens being
the main determinant of allergic airway inflammation. The bell-shaped
exposure response relationship is not modified by the presence of blocking
antibodies and is probably due to a healthy worker effect. The multi-pronged
intervention strategy was effective in reducing airborne flour dust and
allergen levels. It is recommended that further studies investigate the long
term health impact of these interventions in reducing the disease burden.
ACKNOWLEDGEMENTS

I would like to express my sincere thanks and acknowledge the following
people who have contributed to successful completion of this thesis:

My supervisor, Prof Mohamed Fareed Jeebhay and co-supervisors,
Professor Dick Heederik and Dr Tim Meijster (University of Utrecht,
Netherlands), for their insights, guidance, patience and support
Research assistant, Ms Nadia Viljoen and Sisters Leonie Ritchie, Faieza
Omar, Sister Dawn Venter, Sister Shiela Parrot, Sharief Abrahams in
conducting the fieldwork, including the data coding and management
Ms Verne Barnard, Alta Olckers and technologists from the Department
of Respiratory Medicine and Lung Institute of the University of Cape
Town for the pulmonary function and methacholine challenge testing
Prof Rodney Ehrlich and Jonny Myers and support staff, Sharon
Ferguson, Faranaaz Bennett of the Centre for Occupational and
Environmental Health Research Unit in the School of Public Health and
Family Medicine at the University of Cape Town
Dr Shahieda Adams, my friend and colleague for encouragement,
support and comments
Emmanuel Rusford and Shafiek Hassan from the Department of
Environmental and Occupational Studies at the Cape Peninsula
University of Technology for assistance with the collection and analysis of
the environmental samples
Ms Jhurien van Niekerk for data entry and management and Mr Rauf
Sayed and Prof Francesca Little, from the Departments of Public Health
and Statistical Sciences at the University of Cape Town and Professor
Hans Kromhout (University of Utrecht, Netherlands) for statistical advice
and support
SACCAWU, their Shopstewards' Committees and members and
specifically Mr Faghmi Benn who sat on the coordinating committee of
the project
The bakery staff of Pick and Pay in the Western Cape that participated in
the project, including Sisters Tessa van der Walt, Ricardo DuPreez, who
sat on the coordinating committee of the project. A special thanks to Mr
Louis De Beer, head of the national bakery division for his support
Funding support provided by the research grants from the Medical
Research Council of South Africa, National Research Foundation,
THRIPP, Fogarty International Centre and Pick and Pay Bakery division
I want to thank my mom for always encouraging me, believing in me and
supporting me emotionally through this journey.
Finally, I wish to thank my partner, and best friend, Troy Jermaine
Neethling, for his unconditional love, unwavering support and
encouragement.
PREFACE

This thesis includes published papers, as per general provision 6.7 in the
General Rules for the Degree of Doctor of Philosophy (PhD) of the University
of Cape Town, and with the approval in 2013 of the University Doctoral
Degrees Board. The following five papers are formally included as part of the
thesis:

1. Baatjies R, Lopata AL, Sander I, Raulf-Heimsoth M, Bateman E,
Meijster T, Heederik D, Robins TG, Jeebhay MF. Determinants of
asthma phenotypes among supermarket bakery workers.
European Respiratory Journal 2009; 34(4):825-833.

2. Baatjies R, Meijster T, Lopata AL, Sander I, Raulf-Heimsoth M,
Heederik D, Jeebhay MF. Exposure to flour dust in South African
supermarket bakeries: Modeling of baseline measurements of an
intervention study. Ann. Occup. Hyg 2010; 54(3): 309–318

3. Baatjies R, Jeebhay MF. Sensitisation to wheat is a major
determinant of elevated exhaled nitric oxide in bakers. Occup
Environ Med, 2013;70(5):310-316

4. Baatjies R, Meijster T, Heederik D, Jeebhay MF. Exposure-response
relationships for wheat allergen exposure and asthma.
Submitted to Occupational and Environmental Medicine

5. Baatjies R, Meijster T, Heederik D, Sander I, Jeebhay MF.
Effectiveness of interventions to reduce flour dust exposure in
supermarket bakeries.
Submitted to Allergy
The contribution of the candidate to each paper is outlined in the introduction
to each paper. The candidate was the lead author for each paper, prepared
all datasets for the analyses, conducted all the analyses and drafted all
versions of the manuscripts. The candidate was responsible for circulating
the manuscripts to co-authors, reviewing co-author comments and
suggestions before integrating them into the manuscript as appropriate. All
co-authors critically reviewed and approved the submitted manuscripts prior
to submission.
TABLE OF CONTENTS

DECLARATION

ABSTRACT

ACKNOWLEDGEMENTS

Page
CHAPTER 1: INTRODUCTION

1.1 Introduction 2

1.2 Study aim 3

1.3 Objectives of the study 4

1.4 Structure of the thesis 4

1.5 REFERENCES 8

CHAPTER 2: LITERATURE REVIEW

2.1 Background and review of the literature on bakery workers 10

2.2 The baking process and high risk environmental exposure 10
settings

2.3 Constituents of flour dust and potential allergen and their 11
sources

2.4 Epidemiology of allergic sensitisation and asthma 13
associated with flour dust

2.5 Exposure assessment strategies for characterising 18
exposure to flour dust

2.6 Environmental risk factors and exposure-response 32
relationships for flour dust and baker’s asthma

2.7 Host-associated risk factors for allergic sensitisation and 33
asthma associated with flour dust

2.8 Prevention strategies for reducing flour dust exposure and 35
baker's asthma