Research report in partial fulfillment for the degree of MMed (Occupational Medicine) / Background
Occupational asthma is one of the most commonly reported occupational respiratory diseases
in industrialized countries. Literature suggests that about 15% of all adult-onset asthma is
caused by workplace exposures. It is potentially preventable and the prognosis is good with
early diagnosis and adequate treatment. However, occupational asthma is under-diagnosed
and under-reported. Identification of common causative agents and employment of
preventative measures are necessary for proper management and control.
Objectives
1. To characterize occupational asthma cases assessed at NIOH Occupational Medicine
Clinic from 1st January 1997 to 31st December 2007 in terms of:
• types of industries, occupations and agents
• duration of exposure prior to onset of occupational asthma
• time from onset of symptoms to diagnosis
• nature of exposure e.g. intermittent, daily, etc.
2. To investigate factors influencing latency period in cases of sensitizer-induced asthma
3. To investigate factors influencing lag time to diagnosis in cases of sensitizer-induced
asthma
Methods
A record review of a series of cases of occupational asthma was done. All cases of occupational
asthma diagnosed from 1st January 1997 to 31st December 2007 by NIOH doctors were
identified from the Clinic’s electronic database. All the records of patients who had a final
diagnosis of occupational asthma were assessed using a standard data capture sheet. Doubtful
cases were presented at the NIOH Occupational Medicine clinical discussion meeting for a
consensus decision as to whether they qualified to be included in the study or not. Ethical
approval was granted by the University of the Witwatersrand Human Research Ethics
Committee (Medical).
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Results
One hundred and forty two cases of occupational asthma were identified. Of these, 131 were
sensitizer-induced and 11 were irritant-induced asthma. Low molecular-weight agents were in
the majority with isocyanates, welding fumes, vanadium being the most common. Within the
high molecular weight category, wheat was the most common. The majority of cases emanated
from the Engineering, Chemical, Smelter and Food industries. Latency period from first
exposure to development of symptoms was surprisingly long: a mean of 9.8 years and a
median of seven years. The time from onset of symptoms to diagnosis was also long (mean of
4.9 years and median of three years). Younger cases had a shorter latency period and a longer
delay in diagnosis. Agents and jobs for irritant-induced asthma cases varied widely and some
came from unexpected industries.
Discussion
This review of asthma referrals to the NIOH Occupational Medicine Clinic has highlighted
causative industries and identified exposure agents implicated in cases of occupational asthma.
The very wide range of industries, occupations and agents associated with these cases is
suggestive of a wide-spread occupational asthma problem in the region referring cases to the
Clinic. The long latency period and delay in diagnosis are of concern since prompt diagnosis
and removal from exposure is associated with a better prognosis. Irritant-induced asthma is
infrequently reported in the local literature, but the range of agents and jobs is possibly
indicative of under-diagnosis.
Conclusion
Occupational asthma is potentially preventable. New cases still arise particularly in poorly
controlled workplaces which are capable of employing basic measures to control exposures.
Medical surveillance, prompt diagnosis, proper medical management and application of
workplace preventative measures are essential in decreasing the burden of disease and impairment
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/8809 |
| Date | 28 September 2010 |
| Creators | Kgalamono, Spoponki Mamohapi Alina |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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