Some asthmatics may find that their asthma becomes worse at work especially when they breathe in dusts or fumes. This is because their airways or breathing tubes are more irritable or sensitive to the environment as a result of their asthmatic state. However, breathing in air contaminated with specific substances in the form of dusts or fumes may start off or induce asthma in some people with no previous history of asthma. In both situations, the work has a part to play in the asthma. Asthma which is caused or aggravated by the work is called occupational asthma.
There are many substances or agents which can cause occupational asthma. Some common examples are listed in the table. Such lists are updated from time to time as newer agents are being reported.
What are the occupations or industries at risk?
Spray painters, welders, solderers, chemical process workers, insulation workers, bakers, carpenters, pharmaceutical workers, foam mattress manufacturing workers etc may be at risk depending on the type of chemical substances exposed to.
Common Sources of Exposure to Agents Known to Cause Occupational Asthma
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Agents
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Industry/Occupation
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Isocynates
eg TDI, MDI
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Manufacture of foam mattress and cushion
Spray painting
Plastic moulding
Insulation work
Synthetic rubber compounding
Foundry work
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Colophony Resin
(soldering flux)
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Soldering work
eg Electronics Industry
|
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Formaldehyde
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Glues and adhesives
Eg Furniture and Fibreglass Industries
Laboratories
Chemical Industry
|
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Wood Dusts
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Woodworking Industry
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Drugs
eg antibiotics
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Pharmaceutical Industry
Veterinary Products
Animal Feed Industry
|
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Flour/Grain
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Flour Mills
Bakeries
Food Industry
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Metal Salts
eg nickel chromium
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Electroplaters
|
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Amines
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Used as catalysts and hardeners in the Plastic Industry
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Anhydrides
eg pthalic anhydride
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Plastic Industry
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How is Occupational Asthma recognised?
Asthma may be suspected when there are repeated episodes of cough, breathlessness, chest tightness which may or may not be accompanied by wheezing. Occupational Asthma should be suspected when there is a time relationship of the symptoms with exposure to chemicals or agents known or suspected to cause or aggravate asthma. The asthma improves during weekends, long leave or holidays and worsens when back to work. It may require several days or weeks away from work before improvement is noticed. Sometimes, the symptoms come on within minutes of exposure to the particular agent (immediate reaction). Quite often, the asthma may only come on several hours after exposure, example after work in the evenings or late at night (delayed reaction). Asthma due to specific allergy to a particular agent does not manifest on the first exposure to the agent. It may appear after a variable period of exposure ranging from a few days to many years later.
What should you do if you suspect you may have Occupational Asthma?
You should consult your Lung Specialist. The Lung Specialist would take a detailed history of your work exposures and arrange for tests to confirm the presence of asthma and any relationship to your work. Where necessary, a visit to your workplace to evaluate your work environment may be arranged. This has to be arranged by the Occupational Health Clinic, Ministry of Health. If indicated, an inhalational challenge test to the suspected agent may be carried out by the above to confirm the cause of the asthma.
Once occupational asthma is confirmed, it is usually advisable to change your job or be transferred to another section where there is no exposure to the agent causing your asthma. It is therefore important that the diagnosis is based on a thorough and careful investigation.
It is important that occupational asthma is diagnosed early and further exposure to the causative agent stopped. Medication alone may not be able to control the asthma adequately. Continued exposure may result in permanent damage to the airways resulting in persistent asthma even after removal from exposure.
What about Workmen’s Compensation?
Occupational asthma is a compensable disease under the Workmen’s Compensation Act. It is also a notifiable industrial disease. If you are a workman and if the diagnosis of occupational asthma is confirmed, you may apply for Workmen’s Compensation.
How can Occupational Asthma be Prevented?
It is sometimes possible to replace or substitute a substance known to cause the asthma with other safer substances. If this is not possible, then exposure to the agent should be kept as low as is practicable through various means:
• Enclosing the process
• The use of local exhaust ventilation
• The use of respiratory protection
Workers should be well informed of the hazards of the substance that they handle. They should be informed of the risk of occupational asthma and how to recognise it early.