Tadpole Brain Tissue (IMAGE) Brown University Caption Even small concentrations -- 1.5 parts per million -- of a biocide used in cosmetics interrupted neurological development in tadpole brains. There is no evidence those concentrations are harmful to humans. Credit Aizenman lab/Brown University Usage Restrictions Credit required License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.