Under increasing pressure from the federal government, oil giant BP is agreeing to reduce the amount of a chemical dispersant it is using in the Gulf of Mexico...BP uses the dispersant Corexit to try to break up the massive amounts of oil gushing out of its blown-out well in the Gulf, but there are questions about the long-term impact of the chemical on marine wildlife and human health...The Environmental Protection Agency [EPA] raised concerns about the toxicity of Corexit last week, and told the oil company to use a different chemical agent to try to disperse the giant oil slicks...BP officials say their own testing finds the dispersant Corexit effective in breaking up oil and safe to aquatic life -- adding that it couldn't find large enough quantities of other dispersants to make the switch.