On 3 March 2010, the High Court delivered an important decision (Amaca Pty Ltd v Ellis; South Australia v Ellis; Millennium Inorganic Chemicals Ltd v Ellis (2010) 263 ALR 576) holding that the asbestos exposure of a smoker who died of lung cancer was not, on its own, a cause of injury even when the medical and scientific evidence available was unable to definitively attribute the cancer to any particular cause.
Paul Cotton died of lung cancer. He had smoked between 15 and 20 cigarettes a day for over 26 years. He was also exposed to respirable asbestos fibres in the course of his employment with the South Australian Engineering and Water Supply Department (EWSD) and then later with Millennium Inorganic Chemicals Ltd (Millennium). During his employment with EWSD, Mr Cotton worked with asbestos cement pipes manufactured by Amaca (formerly James Hardie & Coy Pty Ltd) (Amaca). The executor of Mr Cotton's estate, Teresa Ellis (plaintiff), sued EWSD, Millennium and Amaca (together, the defendants) in negligence for breaching their duty to provide safe working conditions for Mr Cotton and, as a result, this caused his death.
The issue for determination by the High Court was causation. The essential question was whether the plaintiff had shown that it was more probable than not that the negligence of each defendant was a cause of Mr Cotton's lung cancer. Ultimately, to show this, the plaintiff had to establish that Mr Cotton's exposure to respirable asbestos fibres was, on its own, more probably than not a cause of his lung cancer.
No expert evidence was available to definitively say what had caused Mr Cotton's cancer. The only evidence available was of an epidemiological nature.
The evidence showed that the relative risk of cancer due to smoking was greater than that due to exposure to asbestos. None of the expert witnesses assigned a probability of greater than 23% to Mr Cotton's cancer being caused by asbestos exposure (or a combination of asbestos exposure and smoking). However, all expert witnesses assigned not less than a 67% chance to Mr Cotton's cancer being caused by smoking alone.
One expert, a consultant occupational physician and epidemiologist, suggested that smoking and asbestos exposure had a synergistic effect by operating interdependently and cumulatively to cause lung cancer. However, he also said it was possible to partition attributability to smoking and asbestos under mathematical risk models. The High Court, reading that expert's opinion as a whole, concluded that the expert did not mean that when a smoker has been exposed to asbestos and develops lung cancer, the asbestos exposure is, or is probably, a cause of that cancer.
In rejecting the approach of looking at the risks of Mr Cotton's lung cancer in isolation of each other, the trial judge in the Supreme Court found in favour of the plaintiff, accepting the medical evidence that the synergistic effect between smoking and asbestos exposure caused the two to operate cumulatively towards lung cancer. On that basis, it was found that Mr Cotton's asbestos exposure materially contributed to his lung cancer.
The trial judge also said that the plaintiff would succeed if the evidence established that it was more probable than not that Mr Cotton's lung cancer was caused by asbestos arising from one or both of his periods of occupational exposure to asbestos or if it supported the conclusion, on the balance of probabilities, that his cancer was caused, to a material extent, by the combined effects of his periods of asbestos exposure and the effects of his chronic smoking.
The majority of the Court of Appeal upheld the trial judge's decision. In dissent, Martin CJ held that the approach taken by the trial judge in determining the liability of individual defendants was incorrect. His Honour was of the view that the plaintiff's claim against each defendant should be decided according to whether the negligence of that defendant was a cause of Mr Cotton's cancer. His Honour made clear that deciding whether Mr Cotton's aggregate exposure to asbestos was a cause of his cancer did not answer the question about the particular responsibility of each defendant.
The High Court ultimately found that the evidence did not establish that it was more probable than not that the negligence of any of the defendants, in isolation of each other, was a cause of Mr Cotton's lung cancer because:
- the epidemiological evidence only established that smoking was a more probable cause of Mr Cotton's lung cancer than the asbestos exposure, and
- the evidence did not show that when a smoker has been exposed to asbestos and develops lung cancer, the asbestos exposure is, or is probably, a cause of the cancer.
The High Court further held that material contribution was incorrectly considered by the trial judge as an approach to establishing a causal connection. The High Court explained that the question of material contribution is not a test for causal connection and is only relevant to contribution to the damage suffered where more than one cause of damage has already been established.
In its judgment, the High Court made the following observations:
- it is the role of the court to decide legal causation (on the balance of probabilities) even when science and medicine cannot attribute a cause, and
- in determining causation, questions of material contribution do not arise – material contribution of a cause of damage only arises once the connection between the cause of damage and the damage has been established.
The decision highlights issues of causation in cases involving injuries that have no scientifically proven cause. The important lesson here is that causation will only be established if it can be shown, on the balance of probabilities, that the alleged cause is the cause of the damage and not only that it may be a cause of the damage. This can be contrasted with the position in the United Kingdom where the required standard for causation is met if it can be shown that the asbestos exposure materially increases the risk of the injury suffered. In such circumstances, it would not be necessary to show that the asbestos exposure is a cause of the injury (Fairchild v Glenhaven Funeral Services Ltd (t/a GH Dovener & Son)  1 AC 32).
The decision underlines the significant difficulty a plaintiff may face in establishing asbestos exposure as a cause of damage where he or she has a smoking history. In such circumstances, the plaintiff's success will turn on the individual facts of the asbestos exposure. At this point, epidemiological evidence alone would seem to fall short as a basis for establishing causation. Causation will remain a significant hurdle in asbestos smoking cases, until further developments in science occur or the standard for causation is relaxed in Australia.
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