Fresh analysis of decades-old barrels of toxic waste dumped off of the coast of Los Angeles, California, has solved the mystery of why some are surrounded by ghostly white halos on the seafloor.

The study—undertaken by researchers from Scripps Institution of Oceanography at the University of California , San Diego—highlights the enduring legacy of the pollution, which at the time it was dumped was legal.

The team found that the barrels responsible for producing the eerie halos in the surrounding sediment did not contain the toxic pesticide DDT, as long assumed, but instead some form of highly caustic alkaline waste.

"One of the main waste streams from DDT production was acid and they didn't put that into barrels," Johanna Gutleben, a Scripps postdoctoral scholar and lead author of the

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