BP PLC continues to stockpile and deploy oil-dispersing chemicals manufactured by a company with which it shares close ties, even though other U.S. EPA-approved alternatives have been shown to be far less toxic and...nearly twice as effective. After the...well began gushing crude..., BP quickly marshaled a third of the world's available supply of dispersants, chemicals that break surface oil slicks into microscopic droplets that can sink into the sea. But the benefits...carry uncertain costs. Scientists warn that the dispersed oil, as well as the dispersants themselves, might cause long-term harm...So far, BP has told federal agencies that it has applied more than 400,000 gallons of...Corexit...manufactured by Nalco Co., whose current leadership includes executives from BP...But according to EPA data, Corexit ranks far above dispersants made by competitors in toxicity and far below them in effectiveness in handling southern Louisiana crude...Nalco spokesman Charlie Pajor said the decision on what to use was out of his company's hands. He also declined to comment on EPA comparison tests, saying only that lab conditions cannot necessarily replicate those in the field. [also refers to U.S. Polychemical Corp.]