Asbestosis in workers exposed to asbestos dust in Ontario employment is an occupational disease as peculiar to and characteristic of a process, trade or occupation involving exposure to asbestos.
If the worker was employed in Ontario in any mining, milling, manufacturing, assembling, construction, repair, alteration, maintenance or demolition process involving the generation of airborne asbestos fibres for at least 2 years before the date of diagnosis of asbestosis, the asbestosis is conclusively deemed to have been due to the nature of the employment.
Claims for asbestosis are allowed when it is established that the worker
- has a diagnosis of asbestosis, and
- worked in any mining, milling, manufacturing, assembling, construction, repair, alteration, maintenance or demolition process involving the generation of airborne asbestos fibres.
The legislative requirements of sections 15(5) and 15(6) of the Workplace Safety and Insurance Act for 2 years of asbestos dust exposure in Ontario apply to this policy.
To diagnose asbestosis, the WSIB recognizes histopathological evidence of lung fibrosis due to asbestos and the current diagnostic criteria established by the American Thoracic Society (ATS)*.
* American Thoracic Society: The diagnosis of non-malignant diseases related to asbestos. Am. Rev. Respir. Dis. 134:363-368, 1986.
Current ATS criteria
In the absence of pathologic examination of lung tissue, the diagnosis of asbestosis is made based on a careful consideration of all relevant clinical findings. It is necessary that there is
- a reliable history of asbestos exposure
- an appropriate time interval between exposure and detection.
The ATS regards the following clinical criteria to be of recognized value
- chest roentgenographic evidence of type "s", "t", and "u", small irregular opacifications of a profusion of 1/1 or greater
- a restrictive pattern of lung impairment with a forced vital capacity below the lower limit of normal
- a diffusing capacity below the lower limit of normal
- bilateral late or pan inspiratory crackles at the posterior lung bases not cleared by cough.
When available, positive results from a computerized axial tomography (CAT) scan are also considered for diagnosis of asbestosis.
Asbestosis was entered into Schedule 4 on May 28, 1992. An irrebuttable presumption that the asbestosis was due to the nature of the employment applies to all claims with diagnosis dates on or after May 28, 1992.
This document replaces 04-04-05.
Workplace Safety and Insurance Act, 1997, as amended
Sections 2(1), 15, 94
Board of Directors
#8(XVIII), June 10, 2004, Page 6619