GuLF Study Environmental Health Sciences (NIEHS), part of the National Institutes of Health, and aims to recruit 55,000 of the 150,000 workers who volunteered or were employed to help clean up the spill. It is led by Dale Sandler, head of the NIEHS's epidemiology branch. The "Deepwater Horizon" oil spill was the world's largest accidental marine oil spill. It began on 20 April 2010 after an explosion on the "Deepwater Horizon", a drilling rig leased by BP to drill an exploratory well. Between then and 15 July, when the well was capped, over four million barrels of oil (around 170 million US
BP as a section of the company's website where it communicated its efforts to clean up the spill. BP began a re-branding campaign in late 2010, and decided to focus its brand on the idea of "bringing brilliant minds together with technology at a massive scale to meet the world's energy needs", and focus its messaging on telling stories about people. In February 2012 BP North America launched a $500 million branding campaign to rebuild its brand. The company's advertising budget was about $5 million per week during the four-month spill in the Gulf of Mexico, totaling nearly $100 million. In