On April 20, 2010, the Deepwater Horizon (DWH) Offshore Drilling Unit, located 45 miles southeast of the Louisiana coast, suffered a massive explosion that culminated in a fire which ultimately sunk the unit.  Eleven workers lost their lives and seventeen other workers were injured in the explosion and fire.  Oil began flowing into the Gulf of Mexico soon after the explosion and continued to flow until the well was finally capped on July 15, 2010.  The disaster presented significant challenges in protecting and ensuring the safety of the tens of thousands of responders, geographically spread across the Gulf of Mexico region in Louisiana, Mississippi, Alabama, and Florida.  As part of the response effort, the National Institute for Occupational Safety and Health (NIOSH) supported the Unified Area Command (UAC) by leading several initiatives to help protect DWH responders.  These activities included rostering of workers, conducting health hazard evaluations, providing technical guidance and communication/educational materials, conducting health surveillance activities, and performing toxicity testing on samples of the oil dispersant and the crude oil itself.