What is the standard for determining asbestos exposure was a substantial factor in causing asbestos disease?

In evaluating whether exposure was a substantial factor in causing asbestos disease, the standard should be the same as used in other negligence cases: is there a reasonable medical probability based upon competent expert testimony that the defendant's conduct contributed to plaintiff's injury. ² (Bromme v. Pavitt (1992) 5 Cal.App.4th 1487, 1498, 7 Cal.Rptr.2d 608; Rest.2d Torts, 433B, (1), p. 442.) While there are many possible causes of any injury, " '[a] possible cause only becomes "probable" when, in the absence of other reasonable causal explanations, it becomes more likely than not that the injury was a result of its action. This is the outer limit of inference upon which an issue may be submitted to the jury.' " (Ibid.)