In Holmes v Poeton Holdings Ltd, an employer appealed against a finding that it was liable to its former employee for his contracted Parkinson's disease.
The employee alleged that the employer had acted in breach of common law and statutory duties by exposing him to unsafe levels of trichloroethylene (TCE) in the course of his employment and that exposure had caused his Parkinson's. The judge found that the employer had breached its duties and held that exposure to TCE had made a material contribution to the development of the employee's Parkinson's' and that, accordingly the employer was liable to him for all the consequences of him having contracted Parkinson's.
Parkinson's was an "indivisible disease" in that, once it was contracted, its severity would not be influenced by the total amount of the agent that had caused it. Once a "divisible disease" was initiated, its severity would be so influenced.
At appeal, the employer argued that the judge erred in relying upon a material contribution test for proving causation, because such a test had no application to cases of indivisible injury, and that, even if a material contribution test was applicable, the employee still had to prove that the tortious exposure to TCE from which the employer was responsible had been a "but for" cause of his Parkinson's. However, the authorities showed that the material contribution test applied to indivisible diseases.
The judge had not made specific findings about the duration or levels of exposure. While it would be unreasonable to expect mathematical precision, the likelihood of the exposure having contributed to a mechanism causing Parkinson's had to be affected by the frequency and levels of exposure. Accordingly, the extreme generality of the judge's findings on these points had a knock-on effect when considering what findings had been open to him when he considered general and individual causation.
Further, although the judge had given general descriptions of the levels of exposure, he had not attempted to identify the extent to which any exposure had not been tortious because it had not fallen outside the accepted safe limits, or what the incremental quantity and effect of the tortious exposures could have been.
The evidence on which the judge had relied did no more than establish that TCE was a risk factor for Parkinson's and that there was a plausible mechanism for a finding that TCE could cause or materially contribute to the development of Parkinson's. The evidence to prove generic causation was lacking and did not justify a finding of generic causation.
Given the conclusion about generic causation, the employee could not prove that the tortious exposure to which he had been subjected caused or materially contributed to his Parkinson's unless there were features of his case, not reflected in the generic evidence, that compelled a finding of causation. Such features were absent.
"The evidence as summarised by the judge in support of the hypothesis that exposure to TCE can cause (or materially contribute to the causing of) Parkinson's disease, is weak".
Appeal allowed.
