The Office of the Inspector General (OIG) is providing this science report on our cumulative risk assessment of perchlorate and the other sodium (Na+)/iodide (I-) symporter stressors. This report represents the opinion of the OIG and does not necessarily represent the final position of the U.S. Environmental Protection Agency (EPA). EPA managers will make final determinations on matters in this report. This report contains no recommendations and no further action is required.