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Allens Arthur Robinson

Focus: Causation in lung cancer and other disease cases

9 March 2010

In brief: The High Court of Australia decided1 that the asbestos exposure of a smoker who died of lung cancer was not a cause of his injury. The decision highlights the substantial evidentiary burdens imposed on plaintiffs attempting to prove causation in negligence claims where there is no certain medical or scientific proof of what caused their injuries. Partner Andrew Maher (view CV) reports.

How does it affect you?

  • Establishing causation in cases where the cause/s of a disease or injury is unknown is rarely straightforward. Epidemiological evidence must be sufficiently strong to support an inference that the relevant exposure probably caused the disease or injury.
  • For defendants, it is critical to examine plaintiffs' evidence carefully, including whether plaintiffs have related statistical evidence to their individual circumstances. Absent expert medical and scientific evidence which supports this connection, causation is unlikely to be established.

The facts

Paul Cotton died of lung cancer after smoking between 15 and 20 cigarettes a day for more than 26 years and having been exposed to respirable asbestos fibres during his employment with the South Australian Engineering and Water Supply Department (the Department) and, subsequently, Millennium Inorganic Chemicals Ltd (Millennium). While he was employed by the Department, he worked with asbestos cement pipes, manufactured by Amaca Pty Ltd (formerly James Hardie & Coy Pty Ltd (Amaca). Teresa Ellis (the executor of Mr Cotton's estate) (the plaintiff) sued the Department, Millennium and Amaca, claiming that their negligence had caused Mr Cotton's cancer.

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The issue

The central issue in the case was whether Mr Cotton's asbestos exposure was a cause of his cancer. The court accepted that, although the causes of lung cancer cannot be proven with medical or scientific certainty, the law does not require causation to be established with such certainty. Instead, the court asked whether the plaintiff had proven on the available evidence that it was more probable than not that Mr Cotton's asbestos exposure was a cause of his cancer.

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The trial decision

At trial in the Supreme Court of Western Australia, the plaintiff argued that the court should infer that asbestos exposure caused his cancer, from evidence of epidemiological studies (the study of the distribution and determinants of disease in human populations) suggesting that smoking and, to a much lesser extent, asbestos exposure were positively associated with the risk of contracting lung cancer. None of the experts who gave evidence in the case assigned a probability of greater than 23 per cent to the chance of Mr Cotton's cancer being caused by his asbestos exposure, whereas a much higher probability, of not less than 67 per cent, was attributed to the chance of him contracting cancer from smoking. Nevertheless, the trial judge rejected an approach that looked at these particular risks in isolation because of medical evidence that smoking and asbestos exposure had 'a synergistic effect', in that they operate interdependently and cumulatively to cause lung cancer. On that basis, his Honour decided that asbestos exposure had materially contributed to Mr Cotton's lung cancer. The defendants appealed.

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The appeal decision

The majority of the Court of Appeal upheld the trial judge's decision. In reaching that decision, their Honours rejected the minority judge's view that, if Mr Cotton would have suffered lung cancer because of his smoking irrespective of the defendants' breaches of duty, it could not be said that asbestos exposure also materially contributed to his injury. The defendants appealed to the High Court.

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The High Court decision

In a unanimous judgment, the High Court allowed the appeal, finding that the plaintiff had not established on the evidence that it was more probable than not that the defendants' negligence was a cause of (in the sense of it being a necessary condition for) Mr Cotton's cancer. This decision was based on the following observations:

  • contrary to the views of the Western Australian courts, the medical evidence had not actually established that smoking and asbestos 'work together' and that this had occurred in Mr Cotton's case;
  • the epidemiological evidence merely indicated that smoking was more probably a cause of lung cancer than asbestos exposure; and
  • in any event, no evidence was given to relate the results of the epidemiological studies to Mr Cotton's case.

The court stated that '[o]bserving that a small percentage of cases of cancer were probably caused by exposure to asbestos does not identify whether an individual is one of that group. And given the small size of the percentage, the observation does not, without more, support the drawing of an inference in a particular case'.

In light of the way the case was argued by the plaintiff, the court decided that it was 'not necessary nor appropriate' to consider causation issues addressed in certain United Kingdom and Canadian cases. For example, United Kingdom courts have applied in mesothelioma cases2, a less rigorous causation test (based on policy considerations) which asks merely whether asbestos exposure materially increases the risk of a plaintiff suffering an injury. Arguably similar tests have previously been applied by some judges in Australian cases.3

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Comments

This case emphasises that there are significant evidentiary obstacles that plaintiffs must overcome to prove that exposure to asbestos caused their lung cancer, particularly where they also have had a substantial smoking history. Epidemiological evidence alone is unlikely to be sufficient to overcome those obstacles. This may also be the case for other injuries or diseases that have no scientifically proven cause/s, particularly where the risk of contracting the injury from the alleged cause/s is low compared with other possible causes. Success will usually depend on the strength of that epidemiological evidence and other evidence that relates the population-based findings to individual plaintiffs. Currently, the question of whether the causation test should be relaxed, as it has been in some circumstances overseas, to make it easier for plaintiffs to receive compensation for negligent conduct in these circumstances remains unresolved in Australia.

Footnotes
  1. Amaca Pty Ltd v Ellis, The State of South Australia v Ellis and Millennium Inorganic Chemicals Ltd v Ellis [2010] HCA 5 decided on 3 March 2010.
  2. See Fairchild v Glenhaven Funeral Services Ltd [2003] 1 AC 32, Barker v Corus UK Ltd [2006] 2 AC 572 and Karen Sienkowicz (Administratrix of the Estate of Enid Costello Deceased) v Grief (UK) Limited [2009] EWCA Civ 1159.
  3. See, for example, Bennett v Minister of Community Welfare (1992) CLR 408, per Gaudron J, Chappel v Hart [1998] HCA 55, per McHugh and Kirby JJ, and Naxakis v Western General Hospital (1999) 197 CLR 269, per Gaudron J.

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