High concentrations of DDT found in a vast swath of the California seafloor

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For years, industrial companies in Southern California used the coast as a dumping ground for toxic chemical waste, including DDT. Decades later, scientists discovered that the pesticide remains in high concentrations on the ocean floor and has never broken down.

Nearly two years after the discovery of tens of thousands of barrels of debris off the Los Angeles coast, a scientist working on the issue shared this week that the chemical is still spread across a large stretch of the seafloor, Los Angeles reported. Times.

“We still see original DDT on the seafloor from 50, 60, 70 years ago, which tells us that it’s not breaking down the way it was. [we] I once thought I should,” said David Valentine, a scientist at the University of California, Santa Barbara. The LA Times reported that the contamination covered an area of ​​the seabed larger than the city of San Francisco. “And what we’re seeing now is that there’s DDT ended up everywhere, not just within this tight little circle on a map that we refer to as dump two.”

Related: California’s DDT Waste Legacy: An Undersea Dump Uncovers a Toxic History

DDT, once widely used in the US as an agricultural pesticide and sprayed in large quantities on beaches to kill mosquitoes, has been linked to cancer and disease in humans and to mass animal mortality. In the 1970s, it was banned in the US due to its harmful effects on wildlife and potential risks to humans. Research has shown a link between exposure to the chemical and breast cancer, as well as reproductive problems.

Southern California was the center of DDT production in the United States. Montrose Chemical Corporation in Torrance produced massive quantities of the chemical from the end of World War II until 1982. During that time, before Congress outlawed such activity, up to 2,000 barrels per month of acid sludge waste containing DDT was dumped off the coast. . Workers sometimes made holes in the barrel to make it sink faster.

In late 2020, an LA Times report told the story of how the Los Angeles coast became a dumping ground for DDT, revealing that as many as half a million barrels could still be on the sea floor, leading to Senator Dianne Feinstein to ask the EPA to take action.

A two-week survey, conducted in 2021 by a team from the Scripps Institution of Oceanography at the University of California, San Diego and the National Oceanic Atmospheric Administration, using seafloor robots, acoustic sonar imaging and data, helped reveal the scale of the problem and found more than 25,000 barrels. The scientists identified more than 100,000 man-made items throughout the study area.

A sea lion suffering from a blood infection in Sausalito, California.  Sea lions in California are facing a rise in cancer cases that are potentially linked to thousands of barrels of DDT being dumped into the Pacific Ocean decades ago.

A sea lion suffering from a blood infection in Sausalito, California. Photograph: Justin Sullivan/Getty Images

The scientists’ most recent analysis has found that the most concentrated layer of DDT is about 6 cm deep in the sediment, the Times reported.

“The trawls, the cable runs, could reintroduce these things to the surface,” Valentine told the newspaper. “And the feeding of the animals: if a whale sinks and buries itself at the bottom of the sea, that could lift things up.”

DDT has already been linked to ongoing harmful effects in wildlife. On the central coast of California, which also served as a dumping ground for DDT, a 20-year study found a link between exposure to pollutants and high rates of cancer and herpes in sea lions.

Congress has appropriated millions of dollars to investigate the issue. “The federal funds we obtained will be significant in advancing research to understand the scope and scale of DDT contamination off the coast of southern California,” Feinstein said in Twitter. “We must act quickly to clean this up.”

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