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Occupational disease

As a worker, you may have contracted an occupational disease caused by or in the course of your work. It is important to understand what an occupational disease is, and what steps to take with the CNESST if you contract one.

What is an occupational disease?

It is a disease caused by work, either by the work environment or the tasks related to it.


An occupational disease must be specific to a type of work or directly related to the risks associated with that work. For example, a lung disease such as asbestos is characteristic of work where workers are exposed to asbestos.

Criteria for an occupational disease

As in the case of a work accident, an occupational disease can be contracted out of or in the course of work. It is the CNESST that determines, based on various criteria, whether or not it is an occupational disease.

Disease contracted out of work

When contracted out of work, the disease developed while the worker was performing the tasks for which they are employed (for example, a factory worker who becomes deaf after working in a noisy factory environment for many years).

Disease contracted in the course of work

The occupational disease developed when the worker was performing tasks other than those they normally do. These tasks may be directly or indirectly related to their work.

The worker’s disease will be recognized as an employment injury if, as the case may be:

  • it is listed in the Regulation respecting occupational diseases and the worker meets the specific conditions related to the disease
  • the worker shows that their disease is characteristic of the work they are doing or have done in the past, or that it is directly related to the specific risks associated with the work

In the case of a non-work-related illness, if the worker has to take time off work, their employment relationship is protected.

Steps to take if you contract an occupational disease

If you believe that you have contracted an occupational disease, take the following steps to file a claim.

1) Consult a healthcare professional

If you think you may have contracted a disease caused by or in the course of your work, contract a treating healthcare professional, such as a general practitioner or a specialist, as soon as possible. They will give you the medical certificate required for your claim.

2) Notify your employer as soon as possible, and submit the medical certificate

If you believe that you have contracted an occupational disease, you or another person must notify your employer as soon as possible. Once you have received a medical certificate from your treating healthcare professional, give a copy to your employer as soon as possible.

3) Fill out the Worker’s Claim and the appendix corresponding to your medical situation 

If you believe that you have contracted an occupational disease, you must:

The Worker’s Claim is used to apply to the CNESST for indemnities, for example, if you must take leave from work for more than 14 days. 

Online service for workers

La Réclamation du travailleur (Worker's claim) is a service available from MonEspace CNESST that allows you to claim compensation or reimbursement. By using this service, your file can be processed more quickly.

The CNESST will inform you by email of the status of your file. You will be asked to consult messages and documents placed in this secure space.

Fill in the Worker’s claim


You have 6 months to send us the Worker’s Claim and the corresponding appendix. It is important that you file your claim as soon as possible.

In the case of an occupational disease, you must file the claim within 6 months following:

  • the date on which your treating healthcare professional diagnosed the disease 


  • the date on which you realize the likely connection between your disease and your work

The connection between your disease and your work may be brought to your attention by a medical certificate, a communication from your union, an employer prevention program or the existence of similar cases associated with your occupation.

When you file your claim, send the CNESST all the relevant documents, including your medical certificate and any receipts or prescriptions. This will facilitate the processing of your file. Give a copy of the claim to your employer.

The CNESST will then analyze the admissibility of your claim

Whether it accepts or refuses the claim, when the CNESST renders its decision, it will notify you and your employer in writing. 

For your claim to be admissible, it must be established that you indeed have an occupational disease. The CNESST will determine whether it is related to your work.

If you disagree with the CNESST’s decision, you can contest it.

In the case of an occupational disease, if your claim is accepted, you may be entitled to indemnities, healthcare services and rehabilitation.

If you contracted an occupational disease outside Québec, you may have to choose to receive benefits from the CNESST or from another organization responsible for a compensation plan.

4) Medical examinations

It is important to undergo all of the required medical examinations and to comply with the treatments prescribed by your treating healthcare professional. Other medical examinations may be requested by the CNESST or your employer.

You are obliged to report for medical examinations. Follow your treating healthcare professional’s recommendations to make sure your file is as complete as possible. If you fail to undergo an examination and you are receiving benefits, penalties may apply.

Indemnities, reimbursement and return to work

If you are unable to do your job because of an occupational disease, your employer must pay you 90% of the net salary you would have received for each day or partial day you would normally have worked in the first 14 days following the date you became unable to do your job. 

Your employer must fill out the Avis de l'employeur et demande de remboursement (in French only) for the first 14 days’ leave, send it to the CNESST and give you a copy.

After the first 14 days of leave, if you are entitled to an income replacement indemnity, you will receive the indemnity until the CNESST determines that you are able to do your job or to do a suitable job full time.

You must have filled out a Worker’s Claim to be able to apply for the reimbursement of certain expenses, including medical and travel expenses. You may be reimbursed for these expenses even if you did not have to take leave from work.

Once you know the date of your return to work, you must notify your employer and the CNESST as soon as possible.

Appendices to the Worker’s claim of an occupational disease

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