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Established in 1985, the Workplace Safety and Insurance Appeals Tribunal (WSIAT) is the final level of appeal to which workers and employers may bring disputes concerning workplace safety and insurance matters in Ontario. WSIAT has always been separate from and independent of the Workplace Safety and Insurance Board.



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  Decision 2184 12
S. Martel

  • Exposure (benzene)
  • Leukemia
  • Presumptions (occupational disease)

The worker appealed a decision of the Appeals Resolution Officer denying entitlement for a bone marrow condition, which the worker related to exposure to benzene while working as a truck mechanic from 1984 to 1994 and from 1998 to 2010.
The worker was first diagnosed in 2010 with myeloproliferative disorder (MPD). The worker submitted that his condition progress from MPD to myelofibrosis and then to acute myelogenous leukemia (AML).
There is some dispute in the literature as to the level of benzene associated with AML. There were references to levels of 10 ppm-years and 40 ppm-years. In any event, the worker's average exposure would have been less than 10 ppm-years. More significantly, the accepted association in the literature concerns benzene and AML, not benzene and MPD. However, the medical evidence in this case indicated that the worker's condition had not progressed to AML.
There is a presumption in s. 15(3) of the WSIA that, if a worker was employed in a process set out in Schedule 3 and contracts a disease specified in the Schedule, the disease is presumed to have occurred due to the nature of the worker's employment, unless the contrary is shown. The worker submitted that the presumption applied. However, the Vice-Chair noted that, for the presumption to apply, it must first be determined that the worker is suffering from benzene poisoning. Exposure does not necessarily mean that there was poisoning. In this case, evidence did not suggest that the worker's symptoms were compatible with benzene poisoning. If benzene was implicated, it would have occurred years earlier. Further, the worker's symptoms had all the features of primary myelofibrosis, which is not associated with benzene exposure. Accordingly, the Vice-Chair concluded that the presumption in s. 15(3) did not apply.
Even if the presumption did apply, the Vice-Chair would have found that it was rebutted by evidence to the contrary, in that the exposure was not of a magnitude generally accepted as related to some diseases, that he did not contract the disease associated with benzene exposure and that the latency was not the period associated with disease related to benzene exposure.
The appeal was dismissed.