Jaros

These appeals raise fundamental questions concerning how courts should grapple with causation issues in mass tort cases. The appellants are among thousands of plaintiffs who filed suit for damages allegedly arising out of their exposure to harmful levels of radioactive emissions *1127 from the Hanford Nuclear Reservation over a period of many years. They filed these actions under the Price-Anderson Act, 42 U.S.C. § 2011 et seq., against E.I.' DuPont and other entities who operated the nuclear facility under license agreements with the federal government during the relevant period. Appellants appeal the district court’s summary judgment dismissal of their claims at the end of the second of three scheduled phases of discovery, when the court determined that appellants had not demonstrated individual exposure to a threshold level of radiation the court deemed capable of causing harm. The court established that threshold harmful level by determining the radiation exposure level for each of various categories of plaintiffs, grouped by age and gender, that would double the risk of illness when compared to the risk faced by the general population. That level is sometimes referred to as…