for the pbs newshour, i'm nabil ahmed rufai in hohoe, ghana. >> woodruff: marine scientists say theyidentified more than 25,000 barrels that they believe contain the toxic chemical d.d.t. in the pacific ocean. a massive underwater toxic waste site dating back to world war two has long been suspected off the shore of southern california, given industrial companies had used the ocean as a dumping ground there until 1972. but as stephanie sy reports, the magnitude of this problem was not previously known. >> sy: judy, "staggering", "overwhelming"-- that was how researchers described the amount of these potentially toxic barrels they mapped in a survey last month. the scripps institution of oceanography team used autonomous under water vehicles and sonar to survey 36,000 acres of a dump site that lies between the coast off los angeles and catalina island. for decades, researchers have detected high levels of d.d.t. in marine mammals, including dolphins. sea lions in the area have died of an aggressive cancer. for a deeper look at the iact of the discovery, i'm joined by u.c. santa barbar