Chemical Dumpsite Offshore Southern California

The deep ocean basins off the coast of Los Angeles have been historical dumpsites for various hazardous industrial wastes including the pesticide dichlorodiphenyltrichloroethane (DDT), petrochemical, and other materials. This dumping is known to have occurred from the 1940s until 1972, when the Marine Protection, Research and Sanctuaries Act, also known as the Ocean Dumping Act, was enacted. Contemporary logs show that thousands of barrels of DDT and other chemicals could have been dumped in the basin.


Seafloor Survey

In March 2021, an expedition led by Scripps Institution of Oceanography mapped more than 36,000 acres of seafloor in the San Pedro Basin in a region previously found to contain high levels of the toxic chemical DDT in sediments and the ecosystem. The survey on Research Vessel Sally Ride identified an excess of 27,000 targets with high confidence to be classified as a barrel, and an excess of 100,000 total debris objects on the seafloor.

Read more on this expedition

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In August 2021, scientists from Scripps Oceanography led an expedition off the coast of Southern California to survey the biodiversity of deep sea areas rich in minerals that are of interest to deep sea mining developers around the world. With an underwater robot, the team also explored the DDT dumpsite, collecting sediment and biological samples around six barrels to understand potential ecological effects of the dump site and to determine the levels of DDT present in the ecosystem.  

Read more on this SAMPLING expedition



Funding Awarded for Dumping Site Research

In Sept. 2022, NOAA awarded $5.6 million in spending directed by Senators Dianne Feinstein and Alex Padilla to Scripps Institution of Oceanography. Working with collaborators from UC Santa Barbara and San Diego State University, this new research will aim to fully characterize the extent of the dumpsite, identify the toxin “fingerprint” contained in the sediments, survey the effects of toxins on microbial communities and animals on the seafloor near the site, and assess toxin pathways to the upper ocean, including the potential for exposure to toxins via fish and fisheries. The project will also explore potential remediation strategies, including the capacity for microbes to neutralize the toxins on the seafloor.




Lisa Levin with students aboard research vessel Sproul.


UC San Diego’s Scripps Institution of Oceanography has a variety of scientific experts on this issue. These scientists can provide expertise on methods to identify the scope and condition of the dumpsite, the processes that transport and alter composition of the dumped chemicals, biological pathways that may lead to human exposure these impacts, and more. 


Frequently Asked Questions

The Environmental Protection Agency, Centers for Disease Control and Prevention and California Office of Environmental Health Hazard Assessment have compiled frequently asked questions about the dumpsite and DDT impacts to human health.

EPA: Ocean Disposal Site #2 Investigation

CDC: ToxFAQs for DDT, DDE, and DDD

OEHHA: Legacy Pesticides in Fish and Shellfish

Sealions underwater.

Contact Us

If you are a reporter interested in contacting a researcher to schedule an interview, or are interested in securing a speaker to discuss this issue at an upcoming event, please email