Sienkiewicz v Greif (UK) Ltd [2011] UKSC 10

Mrs Costello worked for Greif at a factory where asbestos was used. Greif negligently exposed her to asbestos dust during her employment, but she also experienced low-level asbestos exposure from the general environment. She later developed mesothelioma and died. Epidemiological evidence suggested that the occupational exposure increased her total risk by about 18 per cent, so it did not more than double the environmental risk. At first instance, Greif was held liable because its breach had materially increased the risk of mesothelioma. The Court of Appeal upheld that result. Greif appealed, arguing that the exceptional Fairchild rule should be confined to multiple-employer cases or that ordinary proof required the occupational exposure to have more than doubled the risk.

Could the Fairchild exception apply to a single negligent employer where another possible source was environmental exposure, and did the claimant have to show that the breach more than doubled the risk?

The Supreme Court dismissed Greif's appeal. The Fairchild exception was not limited to claims against several negligent employers. It applied because mesothelioma's causal mechanism made it impossible to prove which asbestos fibre or exposure initiated the disease, while Greif's breach had materially increased the risk of that very injury. The Court rejected a general rule requiring the claimant to show that the defendant more than doubled the risk. Epidemiological evidence may assist, but the doubling-of-risk approach is not a substitute for legal proof and can be unreliable when the underlying data and competing risks are uncertain. Greif was therefore a responsible person for section 3 of the Compensation Act 2006 and liable for the whole damage, despite the comparatively modest occupational contribution to risk.

The Fairchild material-increase-in-risk exception can apply in a mesothelioma claim against one negligent defendant even when non-tortious environmental exposure is another possible cause. The claimant need not establish that the breach more than doubled the risk; the question is whether the defendant's wrongful exposure materially increased the relevant risk.

The case prevents the exceptional mesothelioma rule from depending on the accidental number of defendants and cautions against converting epidemiological percentages into an inflexible legal test. It must be read with Fairchild, which created the exception, Barker, which explained liability by reference to risk, and section 3 of the Compensation Act 2006, which makes responsible persons liable for the whole mesothelioma damage. The Court left the precise lower boundary of a material increase to be assessed on the evidence rather than defining a universal numerical minimum.