Highlights of Noteworthy Decisions

Decision 2313 15
S. Martel - M. Trudeau - C. Salama
  • Benefit of the doubt
  • Evidence (epidemiological)
  • Exposure (pesticides)
  • Forestry
  • Parkinson's disease

The worker worked at a sawmill from 1966 to 1982. For about six months of each year, he was responsible for the dip vat function, where lumber was immersed in an organochlorine pesticide named Permatox 10s. The worker was diagnosed with Parkinson's disease in 2007, at age 60. The worker appealed a decision of the Appeals Resolution Officer denying entitlement for the Parkinson's disease.

A report from a Tribunal medical assessor reviewed studies in the literature regarding pesticide exposure and development of Parkinson's disease, many of which indicated an odds ratio above or near 2. Other articles suggested a positive correlation. The overall conclusion of the assessor was that the results could be interpreted as confirming an association, but that data failed to demonstrate clearly the nature of the association and that data on specific agents was largely missing.
The Panel noted that, for workplace insurance purposes, it is not necessary to determine the nature of the association nor to ascertain which agents are most associated with development of Parkinson's disease. Decision No. 600/97 set out aspects of statistical association from the Bradford Hill paper that should be considered, including strength of the association, consistency of observed association, specificity of the association, temporal relationship, biological gradient, plausibility, coherence, experiment and analogy.
The Panel also noted that Permatox 10s is composed of Borax and pentachlorophenol (PCP). Borax has not been implicated in any long-term neurological sequelae. PCP is an organochlorine. Permatox 10s is an organochlorine pesticide, similar in structure to other agents in that class, including Dieldrin, for which there is some data suggestive of stronger associations than other agents.
Considering the Bradford Hill criteria, the strength of the association is fairly strong, there is no uniform consistency between studies but the majority appear to show an association, there was plausibility in view of the similar structure to Dieldrin.
Considering the high exposure for six months per year during a 16-year period and the literature, the Panel concluded that the evidence for and against entitlement was at least equal in weight, such that the benefit of doubt applied.
The appeal was allowed.