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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 640 13
B. Kalvin - S. Sahay - A. Grande

  • Exposure (benzene)
  • Medical report (evidence of specialist preferred)
  • Leukemia (hairy cell)

The worker worked at a fuel distribution terminal from 1961 until his retirement in 1990. He was exposed to various chemicals, including benzene. He was diagnosed with hairy cell leukemia (HCL) in 2004, and bladder cancer in 2005. The Board granted the worker entitlement for the bladder cancer. The worker appealed a decision of the Appeals Resolution Officer denying entitlement for the HCL.
HCL is a very rare form of leukemia and, accordingly, there is significantly less epidemiological evidence than for other forms of leukemia. The evidence pertaining to benzene and HCL is mixed and controversial. Some studies suggest no link between benzene and HCL, while other studies suggest that benzene poses a risk for HCL.
It is often difficult for adjudicators to assess the relative reliability and probative value of the various scientific reports. For example, it might not be apparent which reports were published in peer-reviewed journals, or the size of the samples contained in the reports. Accordingly, the Panel attached significant weight to the reports of medical experts who have reviewed the epidemiologic literature and provided their opinions with respect to the facts of the particular case. The reports of these experts indicated that it is possible, but not probable, that the worker's exposure to benzene significantly contributed to the onset of his HCL.
The worker referred to a study on HCL which listed an SIR for benzene of 2. However, the Panel noted that this study only included four cases of persons exposed to benzene. The Panel also noted that there were other studies indicating a significantly lower SIR.
The causes of HCL and the risk factors for the disease are not well understood, although some exposures have been suggested as posing risks. However, the evidence with respect to etiology is unclear.
The worker did not have entitlement for HCL. The appeal was dismissed.