Often people ask which have been the largest mass torts. A major statistical study by two well-known researchers from the Federal Judicial Council analyzes the sizes of the various multidistrict litigations over the years , Willging and Lee, From Class Actions to Multidistrict Consolidations Aggregate Mass-Tort Litigation After Ortiz, 58 U.Kan.L. Rev. 775 (2010).
For each year from 1992 to 2008 they indicate the largest MDLs, based on number of plaintiffs, and what percent of all of the tort cases they were. One first sees breast implants, replaced by fen phen, Baycol, and then Vioxx. The percentages are given of the total mass tort cases pending that year. The extreme was breast implants having 96.5% of all cases in one year. Fen phen hit 67% in another year. The biggest three over all those years are breast implants, diet drugs and welding fumes. These totaled 133,000 cases.