Supreme Court declines to hear case involving St. Louis contamination

The Supreme Court of the United States on Monday declined to hear an appeal from General Atomics subsidiary Cotter Corporation and Commonwealth Edison, an Exelon company, in a case over alleged radioactive contamination in the St. Louis, Mo., area, leaving in place an 8th Circuit Court ruling that allows the plaintiffs' state-law tort claims to proceed under the federal Price-Anderson Act.

The denial came in Cotter Corporation, et al. v. Nikki Steiner Mazzocchio, et al., docket no. 24-1001, according to the court's May 18 orders list and docket. The justices did not explain their decision, as is typical in certiorari denials.

The case: The dispute stems from claims by Nikki Steiner Mazzocchio and Angela Steiner Kraus, who allege that exposure to radioactive waste tied to sites near Coldwater Creek caused them to develop cancer. In an October 2024 decision, the U.S. Court of Appeals for the 8th Circuit affirmed a lower court order declining to dismiss their claims against entities that allegedly handled the waste over the years, including Cotter Corp. and Commonwealth Edison, along with DJR Holdings and the St. Louis Airport Authority.

The companies had asked the Supreme Court to review whether federal nuclear safety regulations preempt state tort standards of care in public liability actions. The 8th Circuit said they do not, concluding that state tort law can still supply the applicable standard in this context. By denying review, the Supreme Court left that ruling intact, allowing the litigation to continue in the lower courts.

Background: Beginning in 1946, residues and wastes from Mallinckrodt's St. Louis uranium processing facility in downtown St. Louis were improperly stored on property near the St. Louis airport and another site near Coldwater Creek. The bulk of the waste, which consisted of low-level radioactive contamination commingled with metals from uranium processing activities, was removed in the past, but residual contamination lingers.

A 2025 study published by the Journal of the American Medical Association claimed to have found an increased rate of cancer for people who grew up living close to Coldwater Creek. The study based its analysis on a cohort of more than 4,200 people who participated in the St. Louis Baby Tooth-Later Life Health Study. From 1958 to 1970, individuals in that study donated their baby teeth to assess exposure to atmospheric nuclear weapons testing.

Since the 1990s, the U.S. Army Corps of Engineers has been cleaning up the creek and surrounding areas under the Formerly Utilized Sites Remedial Action Program.