Highlights of Noteworthy Decisions
- Cancer (lung)
- Evidence (epidemiological)
- Mining (nickel)
The worker was employed at a nickel mine from 1956 to 1984. He was diagnosed with lung cancer in June 1985 and died in September 1985. The worker's estate appealed a decision of the Appeals Resolution Officer denying entitlement for the lung cancer. The Board policy on entitlement for workers with sinter plant exposure provides that it is persuasive evidence that a worker's lung cancer is work-related if the worker worked in any process in the sinter plant as practiced at any time. A previous requirement of six months of work exposure was deleted in 1994. Board practice in interpreting the policy change, as indicated in a memo from the Medical and Occupational Disease Policy Branch (MODPB), was that the absence of a duration requirement affords the adjudicator more discretion but does not mean that any amount of exposure is sufficient for entitlement. MODPB internal guidelines that claims be allowed based on six months of exposure, and be allowed on claims based on less than six months of exposure for non-smokers only. There was no reliable evidence that the worker ever worked in the sinter plant beyond the possibility of a few occasional days of work which, on a cumulative basis, was less than one month. There was epidemiological evidence of an SIR of 193 for one to three months of exposure. The estate submitted that this was close to the SIR of 200, which is considered sufficient for entitlement in Tribunal decisions. However, the Vice-Chair noted that the question of whether a finding is statistically significant relates to the confidence intervals and not to the SIR. The statistical significance may often relate to whether the sample size is sufficient to determine whether the identified SIR reflects more than a chance finding. Thus, the SIR is distinct from the question of statistical significance. Further, to place weight on the association identified in an SIR as evidence of causation, Tribunal decisions have also relied on the Bradford Hill criteria, including whether there is a dose response effect. The estate submitted that the SIR of 193 indicated a 48.25% chance of work-relatedness, which met the standard of significant contributing factor. However, the Vice-Chair stated that the estate was confusing two concepts. It is a misstatement to describe this balance of probability analysis as an analysis of the degree of contribution to the cancer. The 48.25% reflected the probability that the work exposure was a significant contributing factor to the worker's cancer and a 51.75% probability that the work exposure was not a significant contributing factor. The analysis actually indicates that it is more probable than not that there has been no significant contribution by the sinter plan exposure in 51.75% of the cases in the study at the level of one to three months of exposure. Further, although the confidence interval otherwise met for this level of exposure, there was no dose response effect. The Vice-Chair accepted the view of the MODPB that epidemiology does not support a relationship at exposure of less than one month. However, the Vice-Chair did not necessarily accept the recommendation to deny entitlement to workers with less than six months of exposure unless they were non-smokers. That strict limitation is not necessarily consistent with the Board policy, and that it may be appropriate to consider the specific facts of the case for exposure of between one and six months. In any event, the worker did not have even one month of exposure. The epidemiological evidence indicated an SIR of only 47 for exposure of less than one month. The worker also did not have entitlement based on asbestos exposure, as he did not have the 10 years of clear and adequate exposure required by the policy. The appeal was dismissed.