Cancer clusters are never confirmed to have environmental causes by official investigation.

Evidence

“With few exceptions,” said the report, “investigations of leukemia clusters have failed to demonstrate significant associations or even promising leads as to environmental causes.… None of the chemicals found in Wells G and H are known to be leukemogenic, although trichloroethylene and tetrachloroethylene have been found to cause tumors in laboratory animals. The source of the present contaminants is unknown.” — , Harr Jonathan - A Civil Action, 285

Categorization

• QUESTION: The report’s hedge—chemicals causing tumors in animals but not known to be leukemogenic—is exactly the evidentiary gap the whole litigation turns on. Worth chasing how that gap gets bridged in court.
• CANDY: The government’s own cluster study basically concludes ‘we can’t find anything and we don’t know where the pollution came from’—an elevator-ready illustration of why cancer clusters rarely win.
• SEED: Angle: ‘Why official cancer-cluster investigations almost never find a cause’—the methodological and statistical reasons such studies dead-end.