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Work Related Asthma (WRA)

Work-related asthma is a serious breathing disease that is caused by, or made worse by, something in your workplace. There are two types of work-related asthma.

Type 1: Occupational Asthma

  • You did not have asthma prior to joining your workplace.
  • Your asthma is caused by exposures within the workplace.
  • Your symptoms may require you to change jobs.
  • Your asthma symptoms may occur within minutes to hours after exposure.
  • Your asthma symptoms may improve on your days off.
  • As symptoms may not appear immediately and may improve with days off, it can be difficult to recognize the connection to your work.

Substances that can potentially cause occupational asthma to develop:

  • Enzymes (e.g., in detergents or laboratories) and moulds
  • Proteins from animals, plants, foods, insects and fish
  • Fish and shellfish such as snow crab in fisheries and fish processing industries (particularly in Atlantic Canada).
  • Wheat or other flour exposures in bakers
  • Chemicals
  • Isocyanates in spray paints, some glues, foundry moulds, polyurethane foam used in foam products or insulation. Common jobs are roofers, spray painters in the automobile industry, insulators, and/or polyurethane workers.
  • Western red cedar dust in the logging industry in British Columbia.
  • Strong scents
  • Dust

Type 2: Work-Exacerbated Asthma

  • Your pre-existing asthma is made worse by something in the workplace.
  • Certain areas and tasks within your workplace trigger your asthma.
  • How you are affected will depend on how well your existing asthma is controlled.

Substances that can potentially cause work-exacerbated asthma:

  • Smoke
  • Dust
  • Chemicals
  • Fume

At times when your asthma is worse (e.g., during the allergy season if you are usually worse then, or when you have a cold) triggers at work like dust and fumes are likely to bother your asthma more. At times when you have worse asthma symptoms you may need to reduce your work exposure and/or increase your asthma medication.

If your asthma does not improve you may need to remove yourself from that work area for the duration of the allergy season. For more details, read the sections below:

Get an Early Diagnosis

If you become sensitized to a work substance, it is important to talk to your healthcare provider as soon as possible. If you ignore this and keep working in the same area, then your asthma could become permanently worse and may not improve at a later date.

If something in your workplace is causing or worsening your asthma, it is important to get an early diagnosis. It is also vital to take measures to block, or remove yourself from, the exposure. Unfortunately, even low levels of exposure to work sensitizers can worsen your asthma if you are sensitive to them.

Reducing Exposures

If you are exposed to dust, fumes or other triggers for a short time, it may be possible to prevent your asthma from getting worse by wearing a proper fitting mask that is appropriate for the type of exposure (e.g., dust or fumes). You should wear this protective mask even if this is not required by your employer.

When masks (or respirators) are advised by your employer, be sure to wear them. People with asthma are more affected by irritating triggers like dust or fumes than people without asthma.

More Medication

If you are frequently exposed to triggers at your work, and you cannot reduce your exposure to the triggers, you may need more asthma medications to control your asthma.

Change of Job

If you work in jobs where there is constant or frequent exposure to triggers, such as dusts, fumes or sprays, you may have to change your job if your exposure cannot be reduced.

Talk to your healthcare provider

If you think your asthma is worse on work days or better on holidays or days when you are off work, then you should see your healthcare provider and ask if you have work-related asthma. Tell your healthcare provider about the work you do and the substances you are exposed to at work.

Things your healthcare provider may do:

If you have frequent worsenings of asthma at work, your healthcare provider can investigate this by providing you with a peak flow meter and an asthma diary. In the asthma diary you can keep track of your peak flow readings, your inhaler use, and symptoms. The readings taken from days at your workplace can then be compared to the readings taken when you are away from work. The peak flow readings are usually recorded four times per day.

However, if your asthma has been worse only for one or a few days in total at work with some unusual exposure that will not happen again, your healthcare provider may not order any specific tests. You may be able to return to work without seeing a specialist and without further difficulty.

Information to bring to your healthcare provider

If you are exposed to a substance at work then you should ask for a copy of the Material Safety Data Sheet (MSDS) for each substance from your supervisor or health and safety committee. Take these sheets to your healthcare provider.


Your healthcare provider may refer you to a specialist (allergist, respirologist) for additional tests, such as skin tests, to check for changes in your asthma on work weeks compared with times when you are off work.

WRA Medical Tests

Testing for work-related asthma can be quite specialized and is best performed soon after the onset of your work-related symptoms, at the job that you suspect may be affecting you.