The most common long term disease in both children and adults in asthma.

About 5% of adults and 7-10% of children have asthma with many new people finding out they have asthma each year.

In Canada, occupational asthma is considered the most common occupational lung diseases.
It is also one of the most common diseases that goes through the Workers Safety and Insurance Board.

There are over 300 chemicals in the workplace that are known to cause occupational asthma.
Because this list is still growing it is important to find the causes of work related asthma so that it can be controlled and prevented.

What is Asthma?

Asthma is when your small air ways narrow and make is hard to breath.
This means that the air ways have become smaller but can return to normal either on their own or with the use of some medications.

Some symptoms include:

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Chest Tightness

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Difficulty Breathing

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With occupational asthma, there may also be nasal irritation.

Types of Occupational Asthma

Occupational asthma, or work-related asthma, is asthma that happens for the first time because of exposure to some type of agent in the workplace.

It is important to identify this type of asthma to help control the symptoms and prevent it from happening again, or to someone else.
It is important to note that people who have asthma before may also have symptoms that get worse because of something at work.

There are a couple of ways that an asthmatic response can start.

It may be the result of an allergy (allergic occupational asthma) or just to a chemical that irritates the airway.

Allergic Occupational Asthma

Allergic Occupational Asthma is an allergic reaction to something in the workplace.
It might be a chemical or material.

With this type of asthma the symptoms are worse at work and better when off work or at home.
Some people may have few or no symptoms when they are off work.
Allergies develop over time, may be months or years, they are not an instant response.

The term latency period is the time from the first exposure to the development of asthma.

Non-allergic Occupational Asthma or
Reactive Airways Dysfunction Syndrome (RADS)

This type of asthma is caused by a high exposure to a chemical that irritates the airway (e.g. chemical spill, leak or a fire).

This type of asthma usually develops quickly and symptoms often stay for a long period of time.
There is no latency period and this type is not an allergic reaction.

A diagnosis of RADS is based on the following criteria:

RADS Criteria

  1. Symptoms start within 24 hours of the exposure and last for at least 3 months
  2. Exposure to gas, smoke, fumes, vapor that is an irritant at high concentrations
  3. Symptoms begin after a one time exposure
  4. There is no asthma or breathing symptoms before the exposure
  5. Symptoms are asthma like and include cough, wheeze and trouble breathing
  6. There is some airflow problems shown on a pulmonary functions test
  7. All other lung/breathing related disease has been ruled out.

Causes of Occupational Asthma

Isocyanates are a group of highly reactive chemicals and are one of the main groups of chemicals that cause occupational asthma in automotive and foam/plastic parts manufacturing sectors.

Other agents which can cause occupational asthma are anhydrides, metals and metalworking fluids, and lubricants.

Workers at Risk

The auto parts, foam and plastic manufacturing industries have the highest rates of work related asthma.

The following types of workers are at risk from asthma:

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Spray painters, manufacturers of plastic, rubber and foam

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Plastics and epoxy resins workers

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Welders and metal parts manufacturing and fabricating
(e.g. cutting, grinding, drilling, drawing, stamping)

Is My Asthma Work Related?

History, Assessment and Testing

Clinical History

With occupational asthma a pattern usually develops that can show how symptoms are caused by something in the workplace.

This pattern may look like:

  • Wheezing at the start of the work week can happen sometimes within minutes of starting to work or with in one to two hours
  • Relief from wheezing after stopping work or after returning home
  • The symptoms get worse or increase as the work week goes on, usually with relief over the weekends or after days off
  • Sometimes symptoms that occur while at work may be worse late in the evening or may wake you up from your sleep during the night.
  • Sometimes it is hard for a doctor to confirm this diagnosis because they only see the worker away from the work place, such as days of f or after some time of f work. Because symptoms are often less or gone the physician does not have proof to support a diagnosis of occupational asthma. It is very important to tell you doctor where you work, or if you think your asthma might be related to work

Assessing the Work Environment

It is important to take a detailed work history of the workers present and past employment. Sometimes it is hard to pin point the exact chemical or material that is causing the problem so many questions should be asked about what the workers uses at work as well as the workplace in general. Sometimes an occupational hygienist may visit the workplace to help identify hazardous chemicals. It is also important to see if any other workers are having the same symptoms. Symptoms among several workers in a specific area or may give a clue as to what is causing the problem.

Lung Function Testing

There are a couple of test used to help diagnose occupational asthma.

Pulmonary Function Test (PFT's)

Sometimes called a breathing test, this lung test is used to see how well your lungs are working. This test is done by taking a big breath and blowing forcefully and as quickly as possible into a device called a spirometer. The test can be used to show any lung disease or trouble in breathing that may have been caused by something in the workplace. This test can catch a problem that you might not be aware of yet if you are symptom free. It may also show a problem that cannot yet be seen on a chest x-ray. Results that reflect changes caused by the workplace should happen before a shift, after a shift or at the start or end of the work week.

Peak Flow Measurements

You might need to test lung function during a normal working day. The doctor will give you a small, machine called a peak flow meter and show you how to blow in it and record your results. The best of three readings is usually taken and noted ever y two hours between working and sleeping. It may take several days to establish a pattern.

Responsibilities for Prevention

Employer Responsibilities

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 Substitute a material/chemical with a different one that doesn't cause allergic reactions.

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Control exposures using engineering controls. Good, safe enclosures and local exhaust should be provided at all points where dust, vapors, gases and fumes are released. It is also important to know that engineering controls need regular care and should be tested often in order to prevent work hazards such as spills or leaks.

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Provide training to employees on safe working and housekeeping methods to help prevent injuries.

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Implement safe handling procedures and work practices. Showers and company laundered coveralls may be needed. This is important to protect workers who may be exposed.

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Provide personal protective equipment (PPE) to workers and train them on how to use it properly to help reduce illness and injuries.

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Provide respirators if all of the options for controlling the dangers have been looked at and there is still a problem. All workers should be trained in how to use and care for their respirators.

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Tell workers about the dangers in their work area and provide proper training on the safe ways to handle sensitizing materials.

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Consult an occupational hygienist for help dealing with occupational asthma issues in your workplace.

Employee Responsibilities

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Learn about the hazards in the workplace by talking to your health and safety agent

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Follow safe work practices

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Use PPE properly and consistently

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Report any problems with equipment or ventilation systems

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Participate in health and safety programs in your workplace

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Be aware of the early signs of occupational asthma


The treatment of work related asthma starts with control of workplace exposures that have caused or keep making your asthma worse.

Long-term medical treatment of occupational asthma may not be needed if your workplace exposures are controlled.

Sometimes, occupational asthma does not go away even after the exposures are removed.
If this is the case, medical treatment is the same as that for any other asthma.

Drugs that you breathe in (like puffers) are common treatment for asthma. There are different types of these drugs including ones that decrease inflammation and ones for quick, sometimes emergency use.

If you need to use lots of these types of drugs your asthma is not being controlled

Additional Resources

The following resources provide additional information about occupational asthma:

Allergies and Occupational Asthma in Cannabis Production

Health concerns for Cannabis production workers and exposures causing allergies and more.

Work-Related Asthma – Hair, Nail & Beauty Salons

The Lung Association, OHCOW, Health & Safety Ontario

Respiratory Hazards


Kimberly O’Connell, CIH, ROH, CRSP
Kevin Hedges, PhD, COH, CIH
Todd Irick M.Sc, CIH

AirAssess App

This questionnaire style app consists of three scientifically recognized questionnaires on the indoor environment (air quality), job strain (stress), and asthma symptom screening.


October 14, 2015

Part of the OCC-TOBER Webinar Series

Workplace Asthma

October 14, 2015

Dr. Mike Pysklywec, OHCOW (Hamilton)

Where to go for Help

Let your joint health and safety committee member know about your concerns.

Visit your family doctor.

Contact the Occupational Health Clinics for Ontario Workers in your area if you wish to see a health expert who can assess your problems.

Consult your union staff about your options before telling the company of a health reason for changing work.