- Cancer (skin)
- Causation (medical evidence) (standard of proof)
- Evidence (epidemiological)
- Occupational disease (cluster)
The worker was a firefighter, starting in 1980. In June 1994, he was diagnosed with skin cancer on his upper back. In January 2000, he was diagnosed with skin cancer on his shoulder. The worker appealed a decision of the Appeals Resolution Officer denying entitlement for the cancer.The worker in this case was one of eight firefighters whose appeals were combined as a batch appeal, based on all eight workers developing cancer after attending a fire in March 1987. The estate of one of the workers decided not to pursue the appeal. One other appeal was referred back to the Board to be determined under the provisions of O. Reg. 253/07 regarding firefighters who developed lung cancer.Firefighters in the worker's urban area had exposures that were relevant for cancer. A Tribunal medical assessor noted that, although many industrial carcinogens are associated with cancer, relatively few cause skin cancer. Sun exposure is the most common cause of skin cancer.Actinic keratosis is a pre-cancerous condition. The worker had actinic keratosis, which was removed from his face in 1991, before he was diagnosed with skin cancer. Actinic keratosis indicates that the person has suffered sun damage. It is slow growing and likely associated with historical exposure, even dating back to childhood. The medical assessor was of the view that the worker's exposure seemed more consistent with non-occupational factors and that the latency for actinic keratosis was also consistent with non-occupational factors.Even if there is a role for occupational factors in skin cancer, it is necessary to determine whether the worker's risk was increased by such exposure to an extent that made it as likely as not that the work-related exposure was a significant contributing factor to the skin cancer. An epidemiological study indicated an increased risk of 1.39 of skin cancer for firefighters. This was well below the 2 level that would make it as likely as not that the exposure was a significant contributing factor to the cancer.The Panel then considered the exposure at the fire in March 1987. The medical assessor stated that a single day of exposure at that fire would not plausibly cause skin cancer.The Panel then considered the evidence regarding the cluster. The medical assessor noted that, at any given time, some populations will have cancers above the overall rate and other will have cancers below the overall rate. An apparent excess may be consistent with the expected random variability of the cancer.Further, clusters usually consist of the same type of cancer. When a cluster consists of multiple types of cancer without one type predominating, an occupational cause is less likely. The assessor also stated that only primary cancers are used to investigate a cluster. In this cluster, there were two non-cancer diagnoses, and three cancers were of unknown primary, each with a different cellular type. What remained was one liver cancer, one leukemia and two skin cancers.The Panel then considered the standard of proof in an appeal. The appellant referred to the Supreme Court of Canada decision in British Columbia (Workers' Compensation Appeal Tribunal) v. Fraser Health Authority, which concerned a cluster of breast cancer cases. The majority in that decision found that the standard to reach a scientific conclusion was too high an onus of proof and referred to a prior SCC decision as authority for a fact finder to draw a common sense inference of causation in the absence of scientific proof.The Panel accepted that the standard of proof for a workplace insurance claim is the balance of probabilities and that the Panel cannot wait for scientific certainty. However, it is necessary to distinguish between evidence that only suggests a possibility of work-relatedness and evidence that supports the finding that it is as likely as not that workplace exposure was a significant contributing factor to a worker's cancer.The Panel distinguished the Fraser decision on a number of grounds: the Tribunal medical assessor did not restrict her opinions to matters of scientific certainty; the cluster in Fraser involved the same type of cancer; the SMR in Fraser was about 8.There was no "common sense" basis in this case to disagree with the medical assessor on medical issues of latency and compatibility, or regarding exclusion from the cluster.O. Reg. 253/07 has provisions regarding skin cancer that are expected to take effect on January 1, 2017. It recognizes that specific exposures may be sufficiently significant for causation of specific cancers to be presumed after specific periods of time. For skin cancer, the latency period is work as a firefighter for 15 years prior to the diagnosis.In this case, the worker had worked for 14 years prior to the first incidence of skin cancer and 20 years prior to the second incidence. Regarding the first incidence, the worker did not meet the latency threshold. To allow entitlement on the basis that the worker was close to the threshold would essentially change the ambit of the regulation. Regarding the second incidence, the worker met the latency threshold. However, the regulation was not yet in effect. Even if it were in effect, the Tribunal would not be able to address the issue but would have to return it to the Board for adjudication.The Panel concluded that the evidence on record was insufficient for entitlement. Thus, the question of entitlement had to turn on the epidemiology addressing the risk of firefighters for skin cancer. The epidemiology was insufficient to support entitlement on the facts of this case.The appeal was dismissed.