The issue focused on a new study conducted by researchers at the University of Illinois at Urbana-Champaign. They looked at the results of a study in the journal Environmental Research Letters, which compared the health of the animals' brains when they were injected with the radioactive material.

"In this study, we found a very small dose exposure that caused significant changes in brain structure and function," said Dr. Michael J. Lopes, an assistant professor of biological sciences with the university's School of Medicine.