25% of adult and subadult California sea lions have cancer. University of California marine scientist David Valentine may have discovered a cause.

Working with little more than rumors, a hunch, and a robotic submersible, Valentine discovered what had been hidden since the 1940s: countless barrels of toxic waste, laced with DDT, 3,000 feet below the ocean’s surface littering the ocean floor between Long Beach and Catalina Island. 

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