Enid Costello died of mesothelioma in January 2006. From 1966 until 1984 she was an office worker at the defendant's factory premises. The defendant manufactured steel drums and during the course of this process, asbestos dust was released into the factory atmosphere. Although Mrs Costello did not work on the factory floor, her duties took her all over the premises. In common with other inhabitants of the local area, however, she would also have been exposed to a low level of asbestos in the general atmosphere.
The general rule at common law is that a person suffering injury must show on the balance of probabilities that the defendant's tort (most commonly negligence) caused the injury or condition. But for the defendant's wrongdoing, the claimant would not have suffered the damage (this is sometimes called the "but for" test). There is an important exception to this rule. In the case of a "divisible" disease such as pneumoconiosis, the amount of dust inhaled operates cumulatively to cause the disease and determine its severity. If exposure to the dust is partly due to the defendant's negligence and partly not, the defendant will be liable to the extent that his breach of duty has materially contributed to the disease. If there is more than one defendant, liability can be apportioned. This approach, however, causes difficulties in mesothelioma claims because, unlike pneumoconiosis or asbestosis, mesothelioma is an "indivisible" disease. It is still uncertain whether its contraction or its severity can be related to the amount of asbestos fibres ingested, or even which fibres triggered the disease. In Fairchild v Glenhaven , the House of Lords (as it then was) recognised that, in a mesothelioma case where the claimant had been exposed to asbestos at different times while working for different employers, it would be impossible to satisfy the conventional "but for" test and prove which exposure was the cause of the...