one of the causes was more than twice as likely as all the others put together to have caused the disease or injury. By contrast: It does not seem to me that there is any justification for adopting the “doubles the risk” test as the bench mark of what constitutes a material increase of risk. Indeed, if one were to accept Mr Stuart-Smith’s argument that the “doubles the risk” test establishes causation, his de minimis argument would amount to saying that no exposure is material for the purpose of the Fairchild/Barker test unless on balance of probability it was causative of the mesothelioma. This cannot be right. I doubt whether it is ever possible to define, in quantitative terms, what for the purposes of the application of any principle of law, is de minimis. This must be a question for the judge on the facts of the particular case. In the case of mesothelioma, a stage must be reached at which, even allowing for the possibility that exposure to asbestos can have a cumulative effect, a particular exposure is too insignificant to be taken into account, having regard to the overall exposure that has taken place. The question is whether that is the position in this case. I do not think that Judge Main would have dismissed the addition that Greif’s wrongful exposure made to the risk that Mrs Costello would contract mesothelioma as statistically insignificant or de minimis. Commingled product theory In 2005, the Federal Court for the Southern District of New York, considered the issue of causation in the context of an allegation that a gasoline additive, MTBE, had contaminated water supplies (In re Methyl Tertiary Butyl Ether (MTBE) Prods. Liab. Litig., 379 F. Supp. 2d 348, 377 (S.D.N.Y. 2005)). It noted that some of the factors for applying the market share liability doctrine were absent, but stated: [F]rom time to time courts have fashioned new approaches in order to permit plaintiffs to pursue a recovery when the facts and circumstances of their actions raised unforeseen barriers to relief. It developed and applied a new doctrine, 'commingled product theory.' As summarised in 2013 proceedings: Under this theory, when a plaintiff can prove that certain gaseous or liquid products (e.g., gasoline, liquid propane, alcohol) of many refiners and manufacturers were present in a completely commingled or blended state at the time and place that the harm or risk of harm occurred, and the commingled product caused plaintiff’s injury, each refiner or manufacturer is deemed to have caused the harm. Each defendant is then given the opportunity to exculpate itself by proving that its product was not present at the relevant time or in the relevant place, and therefore could not be 45