The trial court prejudicially erred in this asbestosis case in giving a causation instruction based on California law.  In an earlier writ proceeding, the Court of Appeal had held that Michigan law applies to this case, at least as against Marley-Wylain because the plaintiff worked in Michigan while employed by Marley-Wylain and was exposed to asbestos in Michigan during that employment.  Michigan law differs from California law on the causation standard in asbestosis cases.  Under Michigan law, the asbestos exposure for which the defendant bears liability must be shown to have been a substantial factor in causing the plaintiff’s harm.  By contrast, under California law, the plaintiff need merely show that the asbestos exposure was a substantial factor in increasing the risk of contracting asbestosis.  See Rutherford v. Owens-Illinois, Inc. (1997) 16 Cal.4th 953.  Giving the California causation instruction in this case was a prejudicial error as the evidence regarding causation was meager and disputed.