Claimants in mesothelioma cases can prove causation in mesothelioma by establishing a material increase in risk from a defendant’s breach of duty. In most cases to date the process has been straightforward. But as claims move away from the heavier exposure of the 1960s and 70s, the situation changes. When exposure is much lower, what exactly is a material increase in risk? How should courts approach that question?
Mrs Johnstone worked at the defendant’s garage between 1982 and 1989. The maintenance work in the garage included replacement of brake and clutch linings. This was carried out with air lines, which produced a lot of dust. The dust included asbestos. Although Mrs Johnstone typically worked behind closed doors in an office, she would have inhaled some of that dust. She later developed mesothelioma.
At first instance the judge made findings about Mrs Johnstone’s likely exposure to asbestos at the garage. He preferred the defendant’s expert evidence about this and said that it was between 0.001 and 0.002 fibre m/l years. He then decided what increase in risk would be created by that exposure. He concluded that the increase in Mrs Johnstone’s risk of mesothelioma was less than 0.1%. He found that this was not material and the claim failed.
The claimant’s appeal was about the second stage of the judge’s analysis – the translation of the level of exposure into the increase in risk.
The judge’s calculation about the increased levels of risk was based on two research papers. Both have been used before in mesothelioma claims. The first is the 2000 Hodgson & Darnton study. This examined the likely risk created by given levels of exposure to asbestos. The second is the 2009 Peto paper which looked at the general levels of risk of mesothelioma in distinct population cohorts. The H & D paper was used to assess the risk created by Mrs Johnstone’s exposure at work. The Peto study was about the general – or background – risk of those in her age group and sex. A combination of the two led to the judge’s “less than 0.1%” figure.
The claimant criticised the judge’s treatment of the expert evidence about the risk. They said that the Hodgson & Darnton paper was very unreliable in low level exposure cases. They added that the court should have found that a material increase in asbestos exposure was the same as a material increase in risk.
The defendant argued that the judge’s approach was correct. The court had to determine causation by setting the increase in risk from asbestos exposure against the background risk of someone in Mrs Johnstone’s population cohort.
The claimant’s approach was described as “exposure/risk”, and the defendant’s as “direct risk assessment”.
This sounds very much like a category distinction between two opposed principles – but the Court of Appeal explicitly rejected that idea. The key to understanding this complex judgment is there. The Court of Appeal was not rejecting or accepting a particular principle. Instead, they were deciding whether the judge was entitled to come to the decision that he did, based on the evidence that he heard. Most of the claimant’s individual attacks on the judge’s conclusions were rejected. The judge was entitled to come to the view that he did, and the Court of Appeal found for the defendant.
The Court of Appeal also rejected arguments that both the underlying evidence and the causation case should be construed generally in the claimant’s favour. The first was based on the old NIHL case of Keefe v Isle of Man Steam Packet. In Mrs Johnstone’s claim, the defendant should have kept air monitoring records but did not have them. The Court of Appeal explained that the force of this depended on what the relevant documents would have determined. In this case, it was relatively marginal.
The second argument was based on the general Fairchild principle that where a defendant has negligently created a risk and that risk eventuates, the negligent defendant must bear the consequences. The court said that this was the balance already struck by the Fairchild exception.
Finally, the court also rejected the defendant’s secondary argument that materiality of risk could be determined by a chest physician’s clinical assessment (as happened in Bannister).
So what does this all mean for low level exposure cases?
This is clearly a significant success for the defendants. Had the claimant’s arguments succeeded, low level exposure cases would be very difficult to defend.
As we have seen, the Court of Appeal directly rejected the idea that this case laid down a matter of principle as opposed to one of evidence. It is still going to be difficult for either side to move away from the use of the two papers in combination to decide issues of causation. That means that both sides are going to have to concentrate on the “direct assessment” approach. In turn that means the use of occupational hygienists to assess exposure and epidemiological (or similar) experts to put that exposure against an individual's overall risk.
Low level mesothelioma claims may have just become more expensive to run and to defend. Their outcome has also become less easy to predict. This has clear implications for cost. It also affects a claimant lawyer’s ability to assess viable claims at an early stage and carries significant and difficult issues for show cause hearings and Part 34 depositions.
This decision, then, does not lay down hard rules about when a particular increase is material. It says nothing about the judge’s characterisation of a 0.1% increase as immaterial or how bigger or smaller increases might be treated. Nor does it stop parties from following alternative routes to proof, including the use of chest physicians. As the judgment itself recites, “materiality is a question for the judge”. In other words - it’s all about the evidence.
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