As many as half a million barrels of DDT waste were dumped into the ocean off the Southern California coast after World War II, and now a bipartisan bill in Congress wants federal scientists to finally dig into what that toxic legacy is still doing to the water, the fish, and the people who eat them. The Ocean Protection and DDT Reduction Act, introduced in both chambers last week, would put the National Oceanic and Atmospheric Administration in charge of mapping and studying the deep-sea dump sites scattered across the San Pedro Basin.
Sen. Alex Padilla introduced the bill as Senate Bill 5563, and Rep. Salud Carbajal introduced the companion measure as House Resolution 10536, both on September 24, according to GovInfo records. As reported by the Los Angeles Times, Padilla said communities deserve to know what is in the water and what it means for health, fisheries and the future. Padilla, who represents California in the U.S. Senate, and Carbajal, who represents Santa Barbara in the House, are building bipartisan support for the bill, per the same report.
Decades of Dumping Before the Law Changed
DDT — dichlorodiphenyltrichloroethane — was banned more than 50 years ago, but the chemical breaks down over multiple generations rather than disappearing, and scientists have found it in present-day dolphins and coastal-feeding condors, the Los Angeles Times reports. Carbajal said in the same article that communities dependent on a healthy ocean must be protected. From 1947 to 1982, the Montrose Chemical Corporation ran the nation's largest DDT manufacturing plant in Torrance, producing an estimated 800,000 tons of the pesticide and dumping up to 2,000 barrels of acidic sludge into the ocean every month, according to The Guardian.
Much of that waste moved through the sewer system to the Palos Verdes Shelf, a long-identified hot spot alongside the Dominguez Channel, per the Los Angeles Times. The EPA designated 17 square miles of that shelf a federal Superfund site in 1996 after an estimated 110 metric tons of DDT and PCBs accumulated on the ocean floor, according to the U.S. Environmental Protection Agency. In December 2000, the Department of Justice and the California Attorney General finalized a $73 million settlement with Montrose and other corporate defendants for natural-resource rehabilitation and cleanup; prior settlements brought the total collected to about $140 million, the DOJ noted at the time.
Barrels Found Thousands of Feet Down Near Catalina
A UC Santa Barbara research expedition found discarded barrels roughly 3,000 feet underwater near Santa Catalina Island, the Los Angeles Times reports. David Valentine, who led that research team, said the bill's scientific and policy advances could apply to other dump sites along the national coastline, according to the same account. Separately, UC San Diego's Scripps Institution of Oceanography mapped barrels across the seafloor and discovered discarded military explosives from the World War II era during that work.
Scripps surveys conducted in 2021 and 2023 covered 135 square miles of the San Pedro Basin, detecting tens of thousands of discarded industrial items alongside those wartime munitions, using autonomous underwater vehicles and high-resolution sonar to map depths up to 3,000 feet, per Scripps Institution of Oceanography. A September 2025 study led by Scripps researchers found that decaying waste barrels have created localized extremophile hotspots on the deep seafloor, significantly altering marine microbial ecosystems more than 50 years after disposal, as reported by Watchers.News.
A Mix of Toxic Waste Streams, Not Just DDT
A February 2024 investigation by UC Santa Barbara scientists found that many corroded seafloor barrels held low-level radioactive waste rather than DDT, revealing that multiple hazardous waste streams were mixed at offshore disposal sites, according to the Los Angeles Times. The EPA also found that thirteen other Southern California offshore areas had been approved for dumping, which included military explosives, radioactive waste and refinery byproducts, with roughly 3 million metric tons of petroleum waste dumped in total, per the Los Angeles Times. Agency records show at least 14 ocean dump sites were historically designated across Southern California between the 1930s and 1972, stretching from the Channel Islands to the U.S.-Mexico border, according to the EPA.
Congress ended that era in 1972 with the Marine Protection, Research, and Sanctuaries Act, commonly known as the Ocean Dumping Act, which formally banned unpermitted industrial and chemical waste disposal in ocean waters, per GovInfo.
The Toll on Marine Life, and What the Bill Would Fund
The ecological consequences are already visible in the water's apex predators. A 2020 study published in Frontiers in Marine Science documented that 18% to 23% of wild adult California sea lions examined after death suffered from aggressive urogenital carcinoma, with cancer incidence strongly linked to organochlorine contaminants like DDT in their tissue — one of the highest wildlife cancer rates recorded globally. A recent study separately linked DDT to that aggressive cancer in California sea lions, the Los Angeles Times reports.
Mark Gold, director of California Cooperative Oceanic Fisheries Investigations for Scripps Institution of Oceanography, has spent more than 30 years pushing for DDT cleanup and said the bill's passage would be monumental, according to the Los Angeles Times. The legislation designates NOAA as the main coordinating agency, requiring consultation with the EPA, the Department of Defense and other relevant agencies. Carbajal and Padilla propose authorizing $6 million annually through 2034 for a contamination research program that would fund mapping of seafloor contamination, track the spread of DDT and related chemicals through water and the food web, and call for scientists to analyze and explore potential cleanup, including through bioremediation. The bill also seeks to develop tools, technologies and scientific approaches that could be applied to characterize waste disposal impacts at other ocean locations nationwide.
