However, health officials say that the plant does not appear to be the cause of the radioactive fish. Research suggests that, though Vermont Yankee could leak strontium-90 and is currently being tested for it, the timing and levels of the isotope in the fish suggests these are just "background levels" that fish and other animals have been accruing for decades. Um… accruing from where, one might ask? Nuclear weapons tests and other fallout disasters, like Chernobyl, officials say. "Concentrations of Sr-90 detected in the inedible portions of these fish are in the range of what would be expected as a result of fallout from nuclear weapons testing in the 1950s, and the Chernobyl release in 1986," reads a statement from the Vermont Health Department.