The mission found more than 27,000 containers spread over the sea floor off the coast of Los Angeles.
CNN  — 

A recent expedition mapping the seafloor between Los Angeles and Santa Catalina Island found tens of thousands of items likely polluting the ocean with the toxic chemical DDT for decades, according to a news release from the Scripps Institution of Oceanography at the University of California San Diego.

The expedition, which took place in mid-March, used underwater robotic technology to survey more than 36,000 square acres along the seafloor, an area slightly larger than the city of San Francisco, the release said.

Images from the robots show more than 100,000 objects on the ocean floor – more than 27,000 of which are believed to be barrels containing chemicals. Some of those barrels could date back to World War II.

“Unfortunately, the basin offshore Los Angeles had been a dumping ground for industrial waste for several decades, beginning in the 1930s. We found an extensive debris field in the wide area survey,” said Eric Terrill, chief scientist of the expedition and director of the Marine Physical Laboratory at Scripps Institution of Oceanography.

“Now that we’ve mapped this area at very high resolution, we are hopeful the data will inform the development of strategies to address potential impacts from the dumping.”

Terrill noted the dumping pattern found in the seafloor images follows distinct track-line patterns, suggesting dumping was repeatedly done from a moving ship or barge. Some of those tracks measured 11 miles long.

Scripps researchers aboard the Research Vessel Sally Ride recover the REMUS 6000 autonomous underwater vehicle to survey the seafloor.

Montrose Chemical Company of California, which is long since defunct, is believed to have been one of the main polluters, allegedly dumping thousands of DDT-laced barrels in the San Pedro Basin.

In 1990, the Environmental Enforcement Section (EES) filed a lawsuit against the company, according to the Department of Justice. With the last of the claims settled in 2001, the defendants paid $140 million for the EPA and Montrose Settlements Restoration Program (MSRP) to put toward restoring areas impacted by DDT pollution.

DDT, or dichloro-diphenyl-trichloroethane, was first developed in the 1940’s as an insecticide but has since been classified as a probable human carcinogen, suspected to have reproductive effects on humans and has been correlated with liver tumors in animals, according to the Environmental Protection Agency. It is known to be very persistent in the environment.

Scientists have also found high levels of chemicals in certain sea life along the California coast. A December 2020 study in Frontiers in Marine Science stated pollutants such as DDT played a significant role in the development of cancer in mammals.

“Various species of birds in the ocean off Southern California today continue to suffer elevated levels of DDT. Prior to the time Montrose began operations, there were at least 24 nesting pairs of Bald eagles on the Channel Islands, but they all disappeared by the 1950s. By the year 1990, the eagles on Catalina Island were still suffering total reproductive failure from DDT exposure. Peregrine falcons on the Channel Islands also have elevated levels of DDT and their eggshells are approximately 20% thinner than clean peregrine eggs,” according to the DOJ’s Environment and Natural Resources Division.