A new U.S. government study of chemical dispersants used to break up oil from the catastrophic Gulf of Mexico spill shows that when mixed with oil, the dispersant is less toxic to aquatic life than oil alone. The study by the Environmental Protection Agency (EPA) also found that when mixed with oil, the dispersant Corexit 9500A is not more or less toxic than oil mixtures with other chemical dispersants approved for use in oil spills. The EPA released the study results Monday as the Obama administration defended against criticism that officials allowed BP (British Petroleum) to use excessive amounts of chemical dispersants whose threat to aquatic life remains unknown. Congressional investigators allege that the U.S. Coast Guard routinely approved BP requests to use thousands of liters per day of Corexit despite a federal directive to use the chemical sparingly. Representative Edward Markey (Democrat from Massachusetts) said more than 3.8 million liters of toxic dispersants were used to break up the oil as it came out of the well and after it reached the Gulf surface. EPA Administrator Lisa Jackson said that officials have long acknowledged use of dispersants presents environmental trade-offs. The agency took steps to ensure that other response efforts were used instead of dispersants and dramatically reduced dispersant use in late May, she said. Dispersants were last used July 19, four days after a temporary cap was placed on the leaking Macondo well, and dispersant use fell by 72 percent from peak levels following a joint EPA-Coast Guard directive to BP in late May, Jackson said.
