Toxic Waste 'Vanishes' Off California Coast Compounds mysteriously lower along Palos Verdes Shelf By Neal Colgrass, Newser Staff Posted Nov 18, 2013 5:15 PM CST Updated Nov 23, 2013 7:00 PM CST 44 comments Comments The sun sets at the Point Vicente Park on the Pacific Ocean in Palos Verdes, Calif. on Monday, June 22, 2009. (AP Photo/Damian Dovarganes) (Newser) – Scientists are scratching their heads over evidence that toxic waste fouling the California seafloor has begun to disappear—for no real reason, the LA Times reports. A 17-square-mile area off the coast of LA county has long been a horrific dumping ground for the pesticide DDT and industrial compounds known as PCBs. Now, according to recent samples, 90% of them have vanished over the past five years. "The precipitous drop needs to be explained," said an EPA official. "The question we're answering is: Is the DDT still there?" Scientists have their theories: The chemicals may be drifting into the Pacific or could be lying under clean sediment used in a cleanup effort. The compounds are also becoming less toxic as they shed chlorine. But dubious environmentalists are fuming after they won a long legal battle to have manufacturers and the county government pay $140 million to clean the area; an EPA cleanup has been shelved for now. "My guess is it's a little bit of a statistical anomaly," said an oceanographer. "If we sample it again and it's just as clean, then we have a scientific mystery on our hands."