In the context of mass tort litigation, the Louisiana Supreme Court has refined the commonality element, requiring that “each member of the class must be able to prove individual causation based on the same set of operative facts and law that would be used by any other class member to prove causation…. At the time of the hearing on plaintiffs’ motion for class certification in the present case, plaintiffs were asserting causes of action on behalf of a class of some 4,600 property owners for damage caused from 1944 to the present by the emission of toxic chemicals from operations at the wood treating facility. Far from offering the same facts, each member of the proposed class in this case will necessarily have to offer different facts to establish that each defendant’s emissions caused them specific damages on yet unspecified dates (which dates may run into the hundreds or even thousands, considering the 66-year period in question). The causation issue is further complicated by the multitude of alternate sources of PAHs and dioxins in the Alexandria area and on the individual properties of each proposed class member, and by the divergent types of properties encompassed by the proposed class, which include restaurants, occupied and unoccupied residences, industrial and manufacturing complexes, gas stations, agricultural lots, schools, stores, and churches. Whether the properties even have buildings with attics and, if so, the accessibility of those attics are property-specific determinations that will factor into each plaintiff’s proof that the specific harm he suffered surpassed the level of inconvenience that is tolerated under La. Civil Code Article 668. Price v. Martin, 11-0853 (La. 12/6/11), 79 So.3d 960.